android - recyclerview - Usar la vista de reciclador con una base de datos

listview android

Question

Actualmente no hay una implementación predeterminada de RecyclerView.Adapter disponible.

Puede ser con el lanzamiento oficial, Google lo agregará.

Dado que actualmente no hay soporte para CursorAdapter con la visión de reciclador, ¿cómo podemos usar una vista de reciclador con una base de datos? Alguna sugerencia ?

Answer 1

A continuación se muestra mi implementación de cursoradapter para una vista de reciclador. Admite OnItemClickListener, OnLongItemClickListener, OnfooterClickListener, Sections y footer. No es compatible con , encabezado, onHeaderClickListner, desplazamiento rápido, encabezado adhesivo o secciones adhesivas.

Simplemente extienda este adaptador y cree su propio adaptador. Anula los métodos provistos. y pase el cursor del método OnCursorLoadFinished. Si el adaptador ya está creado, swapCursor ()

package com.tracker.paisa;
import android.database.Cursor;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.util.SparseBooleanArray;
import android.view.ViewGroup;
import java.util.ArrayList;
import java.util.List;
/**
* @author Rahul Upadhyay (https://github.com/devDroidRaul)
* Supports footer
* Onitemclicklistener, OnItemLongClickListener, OnFooterClickListener
* Supports Sections.
*
* Does Not support,Header, OnHeaderClickListener, FastScroller, StickySection (this can b done with item decor)
* Pull requests are welcome for improvements.
*
* Override this to give logic to place subheaders between items.
* public abstract boolean onPlaceSubheaderBetweenItems(int position);
*
* create seperate viewHolders for item, subheaders and footer. and return required views.
*
* @Override below methods for individual item type.
* public abstract VH onCreateItemViewHolder(ViewGroup parent, int viewType);
* public abstract SH onCreateSubheaderViewHolder(ViewGroup parent, int viewType);
* public abstract FH onCreateFooterViewHolder(ViewGroup parent, int viewType);
*
* Bind your views with data here.
* @Override below methods to bind data to individual item types.
* public abstract void onBindSubHeaderViewHolder(SH holder, Cursor cursor);
* public abstract void onBindItemViewHolder(VH holder, Cursor cursor);
* public abstract void onBindFooterViewHolder(FH holder, int itemPosition);
*
* Item type -1,-2,-3 are reserved, kindly do not pass them in getItemViewType.
*/
public abstract class RecyclerViewCursorAdapter<SH extends RecyclerView.ViewHolder, VH extends RecyclerView.ViewHolder, FH extends RecyclerView.ViewHolder>
extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
public static final String TAG = RecyclerViewCursorAdapter.class.getSimpleName();
private static final int TYPE_SECTION_HEADER = -1;
private static final int TYPE_MAIN_HEADER = -2;
private static final int TYPE_FOOTER = -3;
// private int headerLayout=0,viewLayout=0;
boolean createHeader;
private List<Integer> subheaderPositions = new ArrayList<>();
private Cursor mCursor;
private boolean mDataValid,footerRequired=false;
private int mRowIDColumn;
private SparseBooleanArray mSelectedItemsIds;
// public RecyclerViewCursorAdapter() { }
//constructor
public RecyclerViewCursorAdapter(Cursor c,boolean footerRequired) {
setHasStableIds(true);
swapCursor(c);
this.footerRequired = footerRequired;
this.mSelectedItemsIds = new SparseBooleanArray();
}
// interface for listning click on recycler view;
public interface OnItemClickedListener{
void OnItemClick(int id, Object data);
void onItemLongClick(int id);
}
OnItemClickedListener onItemClickedListener;
public void setOnItemClickedListener(OnItemClickedListener onItemClickedListener) {
this.onItemClickedListener = onItemClickedListener;
}
public interface OnFooterClickedListener{
void onFooterClick(Object data);
}
OnFooterClickedListener onFooterClickedListener;
public void setOnFooterClickedListener( OnFooterClickedListener onFooterClickedListener){
this.onFooterClickedListener = onFooterClickedListener;
}
public interface OnHeaderClickedListener{
void onHeaderClick(Object data);
}
OnHeaderClickedListener onHeaderClickedListener;
public void setOnHeaderClickedListener( OnHeaderClickedListener onHeaderClickedListener){
this.onHeaderClickedListener = onHeaderClickedListener;
}
private void initSubheaderPositions() {
subheaderPositions.clear();
if(getItemSize() != 0) {
//TODO:Handle This please.
//subheaderPositions.add(0);
} else {
return;
}
for(int i = 1; i < getItemSize(); i++) {
if(onPlaceSubheaderBetweenItems(i - 1)) {
subheaderPositions.add(i + subheaderPositions.size());
}
}
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
initSubheaderPositions();
}
/**
* Called when adapter needs to know whether to place subheader between two neighboring
* items.
*
* @return true if you want to place subheader between two neighboring
* items.
*/
public abstract boolean onPlaceSubheaderBetweenItems(int position);
public abstract VH onCreateItemViewHolder(ViewGroup parent, int viewType);
public abstract SH onCreateSubheaderViewHolder(ViewGroup parent, int viewType);
public abstract FH onCreateFooterViewHolder(ViewGroup parent, int viewType);
public abstract void onBindSubHeaderViewHolder(SH holder, Cursor cursor);
public abstract void onBindItemViewHolder(VH holder, Cursor cursor);
public abstract void onBindFooterViewHolder(FH holder, int itemPosition);
public abstract int getItemSize();
/**
* Return the view type of the item at position for the purposes
* of view recycling.
* Don''t return -1. It''s reserved for subheader view type.
*/
public int getViewType(int position) {
return 0;
}
@Override
public final int getItemViewType(int position) {
if(isSubheaderOnPosition(position)) {
return TYPE_SECTION_HEADER;
} if(footerRequired && getCursor().getPosition()==(getCursor().getCount()-1)){
return TYPE_FOOTER;
}else {
return getViewType(position);
}
}
public boolean isFooterAdded(){
return footerRequired;
}
@Override
public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
Log.d("RVCA-OCVH","create viewholder");
if(viewType == TYPE_SECTION_HEADER) {
return onCreateSubheaderViewHolder(parent, viewType);
} if(footerRequired&&viewType == TYPE_FOOTER){
return onCreateFooterViewHolder(parent, viewType);
}else {
return onCreateItemViewHolder(parent, viewType);
}
}
@SuppressWarnings("unchecked")
@Override
public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
Log.d("RVCA-OBVH","bind viewholder");
Log.d("RVCA-OBVH","subheader position:"+isSubheaderOnPosition(position));
if(isSubheaderOnPosition(position)) {
if (!mDataValid) {
throw new IllegalStateException("Cannot bind viewholder when cursor is in invalid state.");
}
if (!mCursor.moveToPosition(getItemPositionForViewHolder(position))) {
throw new IllegalStateException("Could not move cursor to position " + getItemPositionForViewHolder(position) + " when trying to bind viewholder");
}
onBindSubHeaderViewHolder((SH)holder, mCursor);
}if(footerRequired && position==getItemCount()-1){
Log.d("RVCA-OBVH","bind footerHolder");
onBindFooterViewHolder((FH) holder,position);
} else {
if (!mDataValid) {
throw new IllegalStateException("Cannot bind viewholder when cursor is in invalid state.");
}
if (!mCursor.moveToPosition(getItemPositionForViewHolder(position))) {
throw new IllegalStateException("Could not move cursor to position " + getItemPositionForViewHolder(position) + " when trying to bind viewholder");
}
// if(!mCursor.isAfterLast()) {
// mCursor.moveToPosition(position);
onBindItemViewHolder((VH)holder, mCursor);
}
}
@Override
public final int getItemCount() {
return getItemSize() + subheaderPositions.size()+(footerRequired?1:0);
}
public void notifyDataChanged() {
initSubheaderPositions();
notifyDataSetChanged();
}
public void notifyItemInsertedAtPosition(int itemPosition) {
if (itemPosition == 0) {
if (getItemCount() == 1 || onPlaceSubheaderBetweenItems(itemPosition)) {
subheaderPositions.add(0, 0);
increaseSubheaderPositions(1, 2);
notifyItemRangeInserted(0, 2);
} else {
increaseSubheaderPositions(1, 1);
notifyItemInserted(1);
}
} else if (itemPosition == getItemSize() - 1) {
if (onPlaceSubheaderBetweenItems(itemPosition - 1)) {
subheaderPositions.add(getItemCount() - 1);
notifyItemRangeInserted(getItemCount() - 1, 2);
} else {
notifyItemInserted(getItemPositionInRecyclerView(itemPosition));
}
} else {
if (onPlaceSubheaderBetweenItems(itemPosition - 1) && onPlaceSubheaderBetweenItems(itemPosition)) {
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition - 1);
final int countOfSubheadersBeforePosition = getCountOfSubheadersBeforePosition(itemPositionInRv);
subheaderPositions.add(countOfSubheadersBeforePosition, itemPositionInRv + 1);
increaseSubheaderPositions(countOfSubheadersBeforePosition + 1, 2);
notifyItemRangeInserted(itemPositionInRv + 1, 2);
} else if (onPlaceSubheaderBetweenItems(itemPosition)){
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition - 1);
increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
notifyItemInserted(itemPositionInRv + 1);
} else if (onPlaceSubheaderBetweenItems(itemPosition - 1)) {
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
notifyItemInserted(itemPositionInRv);
} else {
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
notifyItemInserted(itemPositionInRv);
}
}
}
public void notifyItemChangedAtPosition(int itemPosition) {
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
notifyItemChanged(itemPositionInRv);
}
public void notifyItemRemovedAtPosition(int itemPosition) {
final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
for (int i = 1; i < subheaderPositions.size(); i++) {
final int subheaderPosition = subheaderPositions.get(i);
if (subheaderPosition > itemPositionInRv) {
final int previousSubheaderPosition = subheaderPositions.get(i - 1);
if (subheaderPosition - previousSubheaderPosition == 2) {
subheaderPositions.remove(subheaderPositions.indexOf(previousSubheaderPosition));
decreaseSubheaderPositions(subheaderPositions.indexOf(subheaderPosition), 2);
notifyItemRangeRemoved(itemPositionInRv - 1, 2);
} else {
decreaseSubheaderPositions(subheaderPositions.indexOf(subheaderPosition), 1);
notifyItemRemoved(itemPositionInRv);
}
return;
}
}
final int lastSubheaderPosition = subheaderPositions.get(subheaderPositions.size() - 1);
if (itemPositionInRv - lastSubheaderPosition == 1 && getItemCount() == itemPosition + subheaderPositions.size()) {
subheaderPositions.remove(subheaderPositions.size() - 1);
notifyItemRangeRemoved(itemPositionInRv - 1, 2);
} else {
notifyItemRemoved(itemPositionInRv);
}
}
public void setGridLayoutManager(final GridLayoutManager gridLayoutManager) {
gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
@Override
public int getSpanSize(int position) {
if(subheaderPositions.contains(position)) {
return gridLayoutManager.getSpanCount();
} else {
return 1;
}
}
});
}
public boolean isSubheaderOnPosition(int position) {
return subheaderPositions.contains(position);
}
public int getCountOfSubheadersBeforePosition(int position) {
int count = 0;
for(int subheaderPosition : subheaderPositions) {
if(subheaderPosition < position) {
count++;
}
}
return count;
}
public int getItemPositionInRecyclerView(int position) {
int countOfItems = 0;
for (int i = 1; i < subheaderPositions.size(); i++) {
final int previousSubheaderPosition = subheaderPositions.get(i - 1);
final int nextSubheaderPosition = subheaderPositions.get(i);
countOfItems += nextSubheaderPosition - previousSubheaderPosition - 1;
if (countOfItems > position) {
return position + i;
}
}
return position + subheaderPositions.size();
}
public int getItemPositionForViewHolder(int viewHolderPosition) {
return viewHolderPosition - getCountOfSubheadersBeforePosition(viewHolderPosition);
}
private void decreaseSubheaderPositions(int startSubheaderPosition, int decreaseNum) {
for (int i = startSubheaderPosition; i < subheaderPositions.size(); i++) {
final int subheaderPosition = subheaderPositions.get(i);
subheaderPositions.set(i, subheaderPosition - decreaseNum);
}
}
private void increaseSubheaderPositions(int startSubheaderPosition, int increaseNum) {
for (int i = startSubheaderPosition; i < subheaderPositions.size(); i++) {
final int subheaderPosition = subheaderPositions.get(i);
subheaderPositions.set(i, subheaderPosition + increaseNum);
}
}
private List<Integer> getSubheaderPositions() {
return subheaderPositions;
}
public int getSubheaderCount() {
return subheaderPositions.size();
}
public void swapCursor(Cursor newCursor) {
Log.d("RVCA-SC","swap cursor");
if (newCursor == mCursor) {
Log.d("RVCA-SC","same cursor doing nothing");
return;
}
if (newCursor != null) {
Log.d("RVCA-SC","swap cursor not null");
mCursor = newCursor;
mRowIDColumn = mCursor.getColumnIndexOrThrow("_id");
mDataValid = true;
// notify the observers about the new cursor
notifyDataChanged();
} else {
Log.d("RVCA-SC","swap cursor null");
notifyItemRangeRemoved(0, getItemCount());
mCursor = null;
mRowIDColumn = -1;
mDataValid = false;
}
}
public Cursor getCursor(){
return mCursor ;
}
@Override
public long getItemId(int position) {
if (isSubheaderOnPosition(position))
return position;
else {
int cursorPosition = getItemPositionForViewHolder(position);
Cursor cursor = getCursor();
if (hasOpenCursor() && cursor.moveToPosition(cursorPosition)) {
return cursor.getLong(cursor.getColumnIndex("_id"));
}
return NO_CURSOR_POSITION;
}
}
public static final int NO_CURSOR_POSITION = -99;
protected boolean hasOpenCursor() {
Cursor cursor = getCursor();
if (cursor == null || cursor.isClosed()) {
swapCursor(null);
return false;
}
return true;
}
//Methods to do Selection
public void toggleSelection(int position) {
selectView(position, !mSelectedItemsIds.get(position));
}
//Remove selected selections
public void removeSelection() {
mSelectedItemsIds = new SparseBooleanArray();
notifyDataSetChanged();
}
//Put or delete selected position into SparseBooleanArray
public void selectView(int position, boolean value) {
if (value)
mSelectedItemsIds.put(position, value);
else
mSelectedItemsIds.delete(position);
// notifyItemChangedAtPosition(position);
notifyDataSetChanged();
}
//Get total selected count
public int getSelectedCount() {
return mSelectedItemsIds.size();
}
//Return all selected ids
public SparseBooleanArray getSelectedIds() {
return mSelectedItemsIds;
}
public void setSelectedItemIds(SparseBooleanArray selectedItemIds){
this.mSelectedItemsIds=selectedItemIds;
}
}

Answer 2

Como su pregunta dice "Cómo usar RecyclerView con una base de datos" y no está siendo específico, ya sea que quiera SQLite o cualquier otra cosa con RecyclerView, le daré una solución que es sumamente óptima. Utilizaré Realm como base de datos y le permitirá visualizar todos los datos dentro de su RecyclerView . También tiene soporte de consultas asíncronas sin usar Loaders o AsyncTask .

¿Por qué reino?

Paso 1

Agregue la dependencia de gradle para Realm, la dependencia para la última versión se encuentra here

Paso 2

Cree su clase de modelo, por ejemplo, digamos algo simple como Datos que tiene 2 campos, una cadena que se mostrará dentro de la fila RecyclerView y una marca de tiempo que se usará como itemId para permitir que RecyclerView anime elementos. Tenga en cuenta que extiendo RealmObject a continuación debido a que su clase Data se almacenará como una tabla y todas sus propiedades se almacenarán como columnas de esa tabla Data . He marcado el texto de datos como clave principal en mi caso, ya que no quiero que se agregue una cadena más de una vez. Pero si prefiere tener duplicados, haga que la marca de tiempo sea la @PrimaryKey. Puede tener una tabla sin una clave principal, pero le causará problemas si intenta actualizar la fila después de crearla. Una clave primaria compuesta en el momento de escribir esta respuesta no es compatible con Realm.

import io.realm.RealmObject;
import io.realm.annotations.PrimaryKey;
public class Data extends RealmObject {
@PrimaryKey
private String data;
//The time when this item was added to the database
private long timestamp;
public String getData() {
return data;
}
public void setData(String data) {
this.data = data;
}
public long getTimestamp() {
return timestamp;
}
public void setTimestamp(long timestamp) {
this.timestamp = timestamp;
}
}

Paso 3

Cree su diseño para ver cómo debe aparecer una sola fila dentro de RecyclerView . El diseño de un elemento de fila única dentro de nuestro Adaptador es el siguiente

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/area"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:background="@android:color/white"
android:padding="16dp"
android:text="Data"
android:visibility="visible" />
</FrameLayout>

Tenga en cuenta que he mantenido un FrameLayout como raíz a pesar de que tengo un TextView dentro. Planeo agregar más elementos en este diseño y, por lo tanto, lo hice flexible por ahora :)

Para las personas curiosas, así es como se ve un solo artículo en la actualidad.

Etapa 4

Crea tu implementación RecyclerView.Adapter. En este caso, el objeto de fuente de datos es un objeto especial llamado RealmResults que básicamente es LISTA DE ARCHIVOS EN VIVO; en otras palabras, a medida que los elementos se agregan o eliminan de su tabla, este objeto de RealmResults se actualiza automáticamente.

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import io.realm.Realm;
import io.realm.RealmResults;
import slidenerd.vivz.realmrecycler.R;
import slidenerd.vivz.realmrecycler.model.Data;
public class DataAdapter extends RecyclerView.Adapter<DataAdapter.DataHolder> {
private LayoutInflater mInflater;
private Realm mRealm;
private RealmResults<Data> mResults;
public DataAdapter(Context context, Realm realm, RealmResults<Data> results) {
mRealm = realm;
mInflater = LayoutInflater.from(context);
setResults(results);
}
public Data getItem(int position) {
return mResults.get(position);
}
@Override
public DataHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.row_data, parent, false);
DataHolder dataHolder = new DataHolder(view);
return dataHolder;
}
@Override
public void onBindViewHolder(DataHolder holder, int position) {
Data data = mResults.get(position);
holder.setData(data.getData());
}
public void setResults(RealmResults<Data> results) {
mResults = results;
notifyDataSetChanged();
}
@Override
public long getItemId(int position) {
return mResults.get(position).getTimestamp();
}
@Override
public int getItemCount() {
return mResults.size();
}
public void add(String text) {
//Create a new object that contains the data we want to add
Data data = new Data();
data.setData(text);
//Set the timestamp of creation of this object as the current time
data.setTimestamp(System.currentTimeMillis());
//Start a transaction
mRealm.beginTransaction();
//Copy or update the object if it already exists, update is possible only if your table has a primary key
mRealm.copyToRealmOrUpdate(data);
//Commit the transaction
mRealm.commitTransaction();
//Tell the Adapter to update what it shows.
notifyDataSetChanged();
}
public void remove(int position) {
//Start a transaction
mRealm.beginTransaction();
//Remove the item from the desired position
mResults.remove(position);
//Commit the transaction
mRealm.commitTransaction();
//Tell the Adapter to update what it shows
notifyItemRemoved(position);
}
public static class DataHolder extends RecyclerView.ViewHolder {
TextView area;
public DataHolder(View itemView) {
super(itemView);
area = (TextView) itemView.findViewById(R.id.area);
}
public void setData(String text) {
area.setText(text);
}
}
}

Tenga en cuenta que llamo notifyItemRemoved con la posición en la que ocurrió la eliminación pero NO invoco notifyItemInserted o notifyItemRangeChanged porque no hay una forma directa de saber en qué posición se insertó el elemento en la base de datos ya que las entradas Realm no se almacenan de manera ordenada. . El objeto RealmResults se actualiza automáticamente cada vez que se agrega, modifica o elimina un nuevo elemento de la base de datos, por lo que llamamos a notifyDataSetChanged al agregar e insertar entradas masivas. En este punto, probablemente le preocupen las animaciones que no se activarán porque llama a notifyDataSetChanged en lugar de a los métodos de notifyXXX . Es exactamente por eso que el método getItemId devuelve la marca de tiempo para cada fila del objeto de resultados. La animación se logra en 2 pasos con notifyDataSetChanged si llama a setHasStableIds (true) y luego reemplaza getItemId para proporcionar algo que no sea solo la posición.

Paso 5

Vamos a agregar el RecyclerView a nuestra Actividad o Fragmento. En mi caso, estoy usando una Actividad. El archivo de diseño que contiene el RecyclerView es bastante trivial y se vería algo así.

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/recycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="@dimen/text_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />

He agregado una aplicación: layout_behavior porque mi RecyclerView va dentro de un CoordinatorLayout que no he publicado en esta respuesta por brevedad.

Paso 6

Construya RecyclerView en el código y proporcione los datos que necesita. Cree e inicialice un objeto Realm dentro de Crear y ciérrelo en onDestroy de forma similar a cerrar una instancia de SQLiteOpenHelper. En el más simple, su onCreate dentro de la actividad se verá así. El método initUi es donde sucede toda la magia. Abro una instancia de Reino dentro de Crear.

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRealm = Realm.getInstance(this);
initUi();
}
private void initUi() {
//Asynchronous query
RealmResults<Data> mResults = mRealm.where(Data.class).findAllSortedAsync("data");
//Tell me when the results are loaded so that I can tell my Adapter to update what it shows
mResults.addChangeListener(new RealmChangeListener() {
@Override
public void onChange() {
mAdapter.notifyDataSetChanged();
Toast.makeText(ActivityMain.this, "onChange triggered", Toast.LENGTH_SHORT).show();
}
});
mRecycler = (RecyclerView) findViewById(R.id.recycler);
mRecycler.setLayoutManager(new LinearLayoutManager(this));
mAdapter = new DataAdapter(this, mRealm, mResults);
//Set the Adapter to use timestamp as the item id for each row from our database
mAdapter.setHasStableIds(true);
mRecycler.setAdapter(mAdapter);
}

Tenga en cuenta que en el primer paso, solicito a Realm que me proporcione todos los objetos de la clase Data ordenados de manera asincrónica por su nombre de variable llamado datos. Esto me da un objeto RealmResults con 0 elementos en el hilo principal que estoy configurando en el Adaptador. Agregué un RealmChangeListener para recibir una notificación cuando los datos hayan terminado de cargarse desde la secuencia de fondo donde llamo notifyDataSetChanged con mi Adaptador. También llamé a setHasStableIds como verdadero para permitir que la implementación de RecyclerView.Adapter haga un seguimiento de los elementos que se agregan, eliminan o modifican. El comando onDestroy for my Activity cierra la instancia de Realm

@Override
protected void onDestroy() {
super.onDestroy();
mRealm.close();
}

Este método initUi se puede llamar dentro de Crear su actividad o onCreateView o onViewCreated de su Fragmento. Observe las siguientes cosas.

Paso 7

BAM! Hay datos de la base de datos dentro de su RecyclerView cargados asincrónicamente sin CursorLoader, CursorAdapter, SQLiteOpenHelper con animaciones. La imagen GIF que se muestra aquí es un poco lenta, pero las animaciones ocurren cuando agrega elementos o los elimina.

Answer 3

Después de recuperar los datos de DB y almacenarlos en una lista, tal vez debería ser algo como esto:

 dbHelper = new BooksDbAdapter(this);
dbHelper.open();
//Clean all data
dbHelper.deleteAllZist();
//Add some data
dbHelper.insertSomeRecords();
List<String> mylist = dbHelper.getArrayColumn(3);

agregar datos a recyclerview

list = new ArrayList<DataObject>();
Integer i=0;
for (String lst : mylist) {
list.add(i++, new DataObject(lst,
"The RecyclerView widget is a more advanced and flexible
version of ListView."));
}
recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setHasFixedSize(true);
myRecAdapter = new RecyclerviewAdapter(list, Zist1ChapterActivity.this);

Answer 4

Hice un RecyclerViewCursorAdapter usando SortedList como back-end, extendiendo RecyclerView.Adapter

Se puede usar con SQLiteCursor y Loaders

Answer 5

Mi solución fue mantener un miembro CursorAdapter en mi implementación recyclerView.Adapter. Luego pasando todo el manejo de la creación de la nueva vista y uniéndolo al adaptador del cursor, algo como esto:

public class MyRecyclerAdapter extends Adapter<MyRecyclerAdapter.ViewHolder> {
// Because RecyclerView.Adapter in its current form doesn''t natively
// support cursors, we wrap a CursorAdapter that will do all the job
// for us.
CursorAdapter mCursorAdapter;
Context mContext;
public MyRecyclerAdapter(Context context, Cursor c) {
mContext = context;
mCursorAdapter = new CursorAdapter(mContext, c, 0) {
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
// Inflate the view here
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
// Binding operations
}
};
}
public static class ViewHolder extends RecyclerView.ViewHolder {
View v1;
public ViewHolder(View itemView) {
super(itemView);
v1 = itemView.findViewById(R.id.v1);
}
}
@Override
public int getItemCount() {
return mCursorAdapter.getCount();
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
// Passing the binding operation to cursor loader
mCursorAdapter.getCursor().moveToPosition(position); //EDITED: added this line as suggested in the comments below, thanks :)
mCursorAdapter.bindView(holder.itemView, mContext, mCursorAdapter.getCursor());
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
// Passing the inflater job to the cursor-adapter
View v = mCursorAdapter.newView(mContext, mCursorAdapter.getCursor(), parent);
return new ViewHolder(v);
}
}

Answer 6

Puede implementar todos los métodos necesarios usted mismo. Hace poco hice mi propia implementación copiando el código de CursorAdapter.

public class MyAdapter extends RecyclerView.Adapter<ViewHolder> {
protected boolean mDataValid;
protected boolean mAutoRequery;
protected Cursor mCursor;
protected Context mContext;
protected int mRowIDColumn;
protected ChangeObserver mChangeObserver;
protected DataSetObserver mDataSetObserver;
protected FilterQueryProvider mFilterQueryProvider;
public static final int FLAG_AUTO_REQUERY = 0x01;
public static final int FLAG_REGISTER_CONTENT_OBSERVER = 0x02;
public Cursor getCursor() {
return mCursor;
}
//Recommended
public MyAdapter(Context context, Cursor c, int flags) {
init(context, c, flags);
}
public MyAdapter(Context context, Cursor c) {
init(context, c, FLAG_AUTO_REQUERY);
}
public MyAdapter(Context context, Cursor c, boolean autoRequery) {
init(context, c, autoRequery ? FLAG_AUTO_REQUERY : FLAG_REGISTER_CONTENT_OBSERVER);
}
void init(Context context, Cursor c, int flags) {
if ((flags & FLAG_AUTO_REQUERY) == FLAG_AUTO_REQUERY) {
flags |= FLAG_REGISTER_CONTENT_OBSERVER;
mAutoRequery = true;
} else {
mAutoRequery = false;
}
boolean cursorPresent = c != null;
mCursor = c;
mDataValid = cursorPresent;
mContext = context;
mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;
if ((flags & FLAG_REGISTER_CONTENT_OBSERVER) == FLAG_REGISTER_CONTENT_OBSERVER) {
mChangeObserver = new ChangeObserver();
mDataSetObserver = new MyDataSetObserver();
} else {
mChangeObserver = null;
mDataSetObserver = null;
}
if (cursorPresent) {
if (mChangeObserver != null) c.registerContentObserver(mChangeObserver);
if (mDataSetObserver != null) c.registerDataSetObserver(mDataSetObserver);
}
}
// Create new views (invoked by the layout manager)
@Override
public ViewHolder onCreateViewHolder(final ViewGroup parent,
int viewType) {
// create a new view
final View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item, parent, false);
// set the view''s size, margins, paddings and layout parameters
ViewHolder vh = new ViewHolder(view, mCursor, new ViewHolder.IMyViewHolderClicks() {
@SuppressLint("NewApi")
@Override
public void onClick(Cursor cursor) {
Log.e("Item :", cursor.getString(cursor.getColumnIndex(MyDatabaseHelper.MW_NAAM)));
Intent intent = new Intent(TasksListFragment.this.getActivity(), DetailActivity.class);
intent.putExtra(DetailActivity.EXTRA_PARAM_ID, cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));
ActivityOptions activityOptions = ActivityOptions.makeSceneTransitionAnimation(
TasksListFragment.this.getActivity(),
// Now we provide a list of Pair items which contain the view we can transitioning
// from, and the name of the view it is transitioning to, in the launched activity
new Pair<View, String>(
view.findViewById(R.id.imageview_item),
DetailActivity.VIEW_NAME_HEADER_IMAGE),
new Pair<View, String>(
view.findViewById(R.id.textview_name),
DetailActivity.VIEW_NAME_HEADER_TITLE)
);
// Now we can start the Activity, providing the activity options as a bundle
startActivity(intent, activityOptions.toBundle());
// END_INCLUDE(start_activity)
}
});
return vh;
}
// Replace the contents of a view (invoked by the layout manager)
@SuppressLint("NewApi")
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
// - get element from your dataset at this position
// - replace the contents of the view with that element
final Cursor cursor = getItem(position);
holder.mTextView.setText(cursor.getString(cursor.getColumnIndex(MyDatabaseHelper.MW_NAAM)));
holder.mImageView.setTransitionName("grid:image:" + cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));
holder.mTextView.setTransitionName("grid:name:" + cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));
}
//@Override
// public View getView(int position, View view, ViewGroup viewGroup) {
// return view;
// }
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return getCount();
}
public int getCount() {
if (mDataValid && mCursor != null) {
return mCursor.getCount();
} else {
return 0;
}
}
public Cursor getItem(int position) {
if (mDataValid && mCursor != null) {
mCursor.moveToPosition(position);
return mCursor;
} else {
return null;
}
}
@Override
public long getItemId(int position) {
if (mDataValid && mCursor != null) {
if (mCursor.moveToPosition(position)) {
return mCursor.getLong(mRowIDColumn);
} else {
return 0;
}
} else {
return 0;
}
}
public Cursor swapCursor(Cursor newCursor) {
if (newCursor == mCursor) {
return null;
}
Cursor oldCursor = mCursor;
if (oldCursor != null) {
if (mChangeObserver != null) oldCursor.unregisterContentObserver(mChangeObserver);
if (mDataSetObserver != null) oldCursor.unregisterDataSetObserver(mDataSetObserver);
}
mCursor = newCursor;
if (newCursor != null) {
if (mChangeObserver != null) newCursor.registerContentObserver(mChangeObserver);
if (mDataSetObserver != null) newCursor.registerDataSetObserver(mDataSetObserver);
mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
mDataValid = true;
// notify the observers about the new cursor
notifyDataSetChanged();
} else {
mRowIDColumn = -1;
mDataValid = false;
// notify the observers about the lack of a data set
notifyDataSetInvalidated();
}
return oldCursor;
}
public void changeCursor(Cursor cursor) {
Cursor old = swapCursor(cursor);
if (old != null) {
old.close();
}
}
public CharSequence convertToString(Cursor cursor) {
return cursor == null ? "" : cursor.toString();
}
public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
if (mFilterQueryProvider != null) {
return mFilterQueryProvider.runQuery(constraint);
}
return mCursor;
}
public FilterQueryProvider getFilterQueryProvider() {
return mFilterQueryProvider;
}
public void setFilterQueryProvider(FilterQueryProvider filterQueryProvider) {
mFilterQueryProvider = filterQueryProvider;
}
protected void onContentChanged() {
if (mAutoRequery && mCursor != null && !mCursor.isClosed()) {
if (false) Log.v("Cursor", "Auto requerying " + mCursor + " due to update");
mDataValid = mCursor.requery();
}
}
private class ChangeObserver extends ContentObserver {
public ChangeObserver() {
super(new Handler());
}
@Override
public boolean deliverSelfNotifications() {
return true;
}
@Override
public void onChange(boolean selfChange) {
onContentChanged();
}
}
private class MyDataSetObserver extends DataSetObserver {
@Override
public void onChanged() {
mDataValid = true;
notifyDataSetChanged();
}
@Override
public void onInvalidated() {
mDataValid = false;
notifyDataSetInvalidated();
}
}
private final DataSetObservable mDataSetObservable = new DataSetObservable();
public void registerDataSetObserver(DataSetObserver observer) {
mDataSetObservable.registerObserver(observer);
}
public void unregisterDataSetObserver(DataSetObserver observer) {
mDataSetObservable.unregisterObserver(observer);
}
public void notifyDataSetInvalidated() {
mDataSetObservable.notifyInvalidated();
}
}

Answer 7

Si está ejecutando una consulta con un CursorLoader y desea RecyclerView en lugar de ListView.

Puedes probar mi CursorRecyclerViewAdapter: CursorAdapter en RecyclerView

Answer 8

Solo otra respuesta, ya que no me gustó la aceptada (que no tiene un uso intuitivo).

La siguiente es mi propia implementación, que es muy similar a (y parcialmente inspirada por) SimpleCursorAdapter :

public class RecyclerViewSimpleCursorAdapter extends RecyclerView.Adapter {
private int mLayout;
private Cursor mCursor;
private String[] mFrom;
private int[] mTo;
private boolean mAutoRequery;
private ContentObserver mContentObserver;
/**
* Standard constructor.
*
* @param layout resource identifier of a layout file that defines the views for this list item. The layout file should include at least those named views defined in "to"
* @param c The database cursor. Can be null if the cursor is not available yet.
* @param from A list of column names representing the data to bind to the UI. Can be null if the cursor is not available yet.
* @param to The views that should display column in the "from" parameter. These should all be TextViews and ImageViews. The first N views in this list are given the values of the first N columns in the from parameter. Can be null if the cursor is not available yet.
*/
public RecyclerViewSimpleCursorAdapter(int layout, Cursor c, String[] from, int[] to, boolean autoRequery) {
mLayout = layout;
mCursor = c;
mFrom = from;
mTo = to;
mAutoRequery = autoRequery;
if (mAutoRequery) {
initializeContentObserver();
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new RecyclerView.ViewHolder(
LayoutInflater.from(parent.getContext())
.inflate(mLayout, parent, false)
) {
};
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
mCursor.moveToPosition(position);
if (mFrom == null || mTo == null)
return;
for (int i = 0; i < mFrom.length && i < mTo.length; i++) {
String from = mFrom[i];
int columnIndex = mCursor.getColumnIndex(from);
String value = mCursor.getString(columnIndex);
View view = holder.itemView.findViewById(mTo[i]);
if (view instanceof TextView) {
((TextView) view).setText(value);
} else if (view instanceof ImageView) {
try {
((ImageView) view).setImageResource(Integer.parseInt(value));
} catch (NumberFormatException nfe) {
((ImageView) view).setImageURI(Uri.parse(value));
}
} else {
throw new IllegalStateException(view.getClass().getName() + " is not a view that can be bound by this RecyclerViewSimpleCursorAdapter");
}
}
}
@Override
public int getItemCount() {
return mCursor != null ? mCursor.getCount() : 0;
}
private void initializeContentObserver() {
mContentObserver = new ContentObserver(new Handler()) {
@Override
public boolean deliverSelfNotifications() {
return true;
}
@Override
public void onChange(boolean selfChange) {
notifyDataSetChanged();
}
};
mCursor.registerContentObserver(mContentObserver);
}
/**
* Change the underlying cursor to a new cursor. If there is an existing cursor it will be closed.
*
* @param cursor The new cursor to be used
*/
public void changeCursor(Cursor cursor) {
Cursor oldCursor = mCursor;
if (mAutoRequery) {
if (mCursor != null) {
mCursor.unregisterContentObserver(mContentObserver);
}
mContentObserver = new ContentObserver(new Handler()) {
@Override
public boolean deliverSelfNotifications() {
return true;
}
@Override
public void onChange(boolean selfChange) {
notifyDataSetChanged();
}
};
mCursor = cursor;
if (mCursor != null) {
mCursor.registerContentObserver(mContentObserver);
}
}
notifyDataSetChanged();
if (oldCursor != null && oldCursor != mCursor) {
oldCursor.close();
}
}
/**
* Change the cursor and change the column-to-view mappings at the same time.
*
* @param cursor The database cursor. Can be null if the cursor is not available yet.
* @param from A list of column names representing the data to bind to the UI. Can be null if the cursor is not available yet.
* @param to The views that should display column in the "from" parameter. These should all be TextViews or ImageViews. The first N views in this list are given the values of the first N columns in the from parameter. Can be null if the cursor is not available yet.
*/
public void changeCursorAndColumns(Cursor cursor, String[] from, int[] to) {
mFrom = from;
mTo = to;
changeCursor(cursor);
}
/**
* Returns the cursor.
* @return the cursor
*/
public Cursor getCursor() {
return mCursor;
}
}

Puede modificarlo para otros usos particulares, pero tener un cursor funciona igual que SimpleCursorAdapter , solo con un RecyclerView .

Answer 9

Simplest implementation is to use cursor object in the adapter and pass cursor to viewholder constructor for modifying views and change the cursor position in onBindViewholder.

If you are using cursor Loader call the setCursor method in onLoadfinished() and passing null in onLoadReset()

public class PetCursorRecyclerViewAdapter extends RecyclerView.Adapter<PetCursorRecyclerViewAdapter.ViewHolder> {
Cursor cursor = null;
Context context;
public PetCursorRecyclerViewAdapter(Context context) {
this.context = context;
}
public void setCursor(Cursor cursor) {
this.cursor = cursor;
notifyDataSetChanged();
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(context).inflate(R.layout.catalog_item, parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
this.cursor.moveToPosition(position);
holder.bindModel(this.cursor);
}
/* getItemCount() returns the count of videos from the Cursor, or 0 if the
Cursor is null (mimicking the behavior of CursorAdapter, which also treats
a null Cursor as merely being one that has no rows)*/
@Override
public int getItemCount() {
if (cursor == null) {
return 0;
} else {
return cursor.getCount();
}
}
public static class ViewHolder extends RecyclerView.ViewHolder {
private TextView name_tv, breed_tv;
public ViewHolder(View itemView) {
super(itemView);
name_tv = (TextView) itemView.findViewById(R.id.name_tv);
breed_tv = (TextView) itemView.findViewById(R.id.breed_tv);
}
public void bindModel(Cursor cursor) {
int name_index = cursor.getColumnIndexOrThrow(PetsContract.PetEntry.COLUMN_PET_NAME);
int breed_index = cursor.getColumnIndexOrThrow(PetsContract.PetEntry.COLUMN_PET_BREED);
name_tv.setText(cursor.getString(name_index));
String breed = cursor.getString(breed_index);
if (TextUtils.isEmpty(breed)) {
breed = "Unknown Breed";
}
breed_tv.setText(breed);
}
}

}

Answer 10

You can use SQLite database to store the details. It is easy to access the data. You can check my code on github. https://github.com/thiru-wta/ToDo

 database = new Database(this);
getSupportActionBar().setTitle("To Do List");
etAddItems = (EditText) findViewById(R.id.etAddItem);
btnAdd = (Button) findViewById(R.id.btnAdd);
mRecyclerView = (RecyclerView) findViewById(R.id.listView);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new RecyclerAdapter(this, listData);
mRecyclerView.setAdapter(adapter);
btnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
event_name = etAddItems.getText().toString();
String getname="";
database.storeEventDetails(event_name);
getname = database.getEventDetails(event_name);
if (getname.length() != 0) {
listData.add(getname);
etAddItems.setText("");
adapter.notifyData(listData);
}

Database methods:

 public void storeEventDetails(String event_name, long timerStart) {
SQLiteDatabase db1 = getWritableDatabase();
db1.execSQL("insert into ''"+event_details_tbl+"'' values(''" + event_name + "'')");
db1.close();
}

get method:

 public String getEventDetails(String event_name) {
SQLiteDatabase db1 = getReadableDatabase();
Cursor cur = db1.rawQuery("select * from ''"+event_details_tbl+"'' where event_name =''" + event_name + "''", null);
cur.moveToFirst();
String evName = null;
if (cur != null) {
do {
int eventName = cur.getColumnIndex("event_name");
String ev_name = cur.getString(eventName);
evName = ev_name;
} while (cur.moveToNext());
}
cur.close();
db1.close();
return evName;
}

Answer 11

You have simply to follow these steps:

• In the recycler view.adapter , create an ArrayList or an Iterator initialized with a null value.
• Create a method like the ex swapcursor, for example swapdata(Arraylist<T> data) . Inside you give a new values to the array list, iterator or any structure that system can iterate using the integer position int the bindview. The values of this method are passed in the onloaderfinished() . Then call in just after assignement notifydatachange() ; these will ask the RecyclerView to redraw all the list with new data of the ArrayList.

In the activity or fragment where you are using the loadercalback, create a method that transforms the cursor to an arraylist, or iterator, depending on the data structure chosen in the adapter.

This way you can always use the loadercalback with out blocking the main thread.