studio - zoom en pantalla android

Zoom de zoom de zoom de escala de Android en el lienzo

Question

Necesito agregar las siguientes funciones en mi aplicación

Tengo que mostrar Bitmap en Canvas

Luego, el usuario puede acercar y alejar el mapa de bits en Canvas

¿Cómo hacerlo posible? Solo lo necesito en Canvas, no en ImageView

Todas las respuestas no son de mucha ayuda para mí ... entonces pienso actualizar mi pregunta

Básicamente, necesito un simple botón 2 y un lienzo ...

al hacer clic en el primer botón, la imagen en el lienzo puede rotar / acercar y alejar y al hacer clic en el segundo botón debe mostrar la imagen ampliada o alejada creada por el usuario y luego el usuario no debe poder acercarla o alejarla

Answer 1

Si amplía y aleja el mapa de bits en el lienzo, use el código siguiente que

Agrega tu código en tu actividad

MyView myView = new MyView(this);
    setContentView(myView);

y debajo de tu vista

public class MyView extends View {
private Drawable image;
private ScaleGestureDetector scaleDetector;
private float scaleFactor = 1.f;

public MyView(Context context) {
    super(context);
    init(context);
}

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}

public MyView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init(context);
}

private void init(Context ctx) {
    image = getResources().getDrawable(R.drawable.ic_launcher);
    image.setBounds(0, 0, image.getIntrinsicWidth(),
            image.getIntrinsicHeight());
    scaleDetector = new ScaleGestureDetector(ctx, new ScaleListener());
}


@Override
protected void onDraw(Canvas canvas) {
    canvas.save();
    canvas.scale(scaleFactor, scaleFactor);
    image.draw(canvas);
    canvas.restore();

};

@Override
public boolean onTouchEvent(MotionEvent ev) {
    scaleDetector.onTouchEvent(ev);
    return true;
}

private class ScaleListener extends
        ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scaleFactor *= detector.getScaleFactor();
        scaleFactor = Math.max(0.1f, Math.min(scaleFactor, 10.0f));
        invalidate();
        return true;
    }
}
}

Answer 2

Puede usar esta clase de vista personalizada, proporciona arrastre junto con el efecto de zoom. No soy el autor original de esta clase, lo copié de este tutorial . Puede ir a través de páginas de tutoriales si desea ver paso a paso cómo lograr este efecto.

public class ZoomView extends View {

        //These two constants specify the minimum and maximum zoom
        private static float MIN_ZOOM = 1f;
        private static float MAX_ZOOM = 5f;

        private float scaleFactor = 1.f;
        private ScaleGestureDetector detector;

        //These constants specify the mode that we''re in
        private static int NONE = 0;
        private static int DRAG = 1;
        private static int ZOOM = 2;

        private int mode;

        //These two variables keep track of the X and Y coordinate of the finger when it first
        //touches the screen
        private float startX = 0f;
        private float startY = 0f;

        //These two variables keep track of the amount we need to translate the canvas along the X
        //and the Y coordinate
        private float translateX = 0f;
        private float translateY = 0f;

        //These two variables keep track of the amount we translated the X and Y coordinates, the last time we
        //panned.
        private float previousTranslateX = 0f;
        private float previousTranslateY = 0f;    

        public ZoomView(Context context) {
            super(context);
            detector = new ScaleGestureDetector(getContext(), new ScaleListener());
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {

            switch (event.getAction() & MotionEvent.ACTION_MASK) {

                case MotionEvent.ACTION_DOWN:
                    mode = DRAG;

                    //We assign the current X and Y coordinate of the finger to startX and startY minus the previously translated
                    //amount for each coordinates This works even when we are translating the first time because the initial
                    //values for these two variables is zero.               
                    startX = event.getX() - previousTranslateX;
                    startY = event.getY() - previousTranslateY;
                    break;

                case MotionEvent.ACTION_MOVE:               
                    translateX = event.getX() - startX;
                    translateY = event.getY() - startY;

                    //We cannot use startX and startY directly because we have adjusted their values using the previous translation values. 
                    //This is why we need to add those values to startX and startY so that we can get the actual coordinates of the finger.
                    double distance = Math.sqrt(Math.pow(event.getX() - (startX + previousTranslateX), 2) + 
                                                Math.pow(event.getY() - (startY + previousTranslateY), 2)
                                               );

                    if(distance > 0) {
                       dragged = true;
                    }               

                    break;

                case MotionEvent.ACTION_POINTER_DOWN:
                    mode = ZOOM;
                    break;

                case MotionEvent.ACTION_UP:
                    mode = NONE;
                    dragged = false;

                    //All fingers went up, so let''s save the value of translateX and translateY into previousTranslateX and 
                    //previousTranslate           
                    previousTranslateX = translateX;
                    previousTranslateY = translateY;
                    break;

                case MotionEvent.ACTION_POINTER_UP:
                    mode = DRAG;

                    //This is not strictly necessary; we save the value of translateX and translateY into previousTranslateX
                    //and previousTranslateY when the second finger goes up
                    previousTranslateX = translateX;
                    previousTranslateY = translateY;
                    break;       
            }

            detector.onTouchEvent(event);

            //We redraw the canvas only in the following cases:
            //
            // o The mode is ZOOM 
            //        OR
            // o The mode is DRAG and the scale factor is not equal to 1 (meaning we have zoomed) and dragged is
            //   set to true (meaning the finger has actually moved)
            if ((mode == DRAG && scaleFactor != 1f && dragged) || mode == ZOOM) {
                invalidate();
            }

            return true;
        }

        @Override
        public void onDraw(Canvas canvas) {
            super.onDraw(canvas);

            canvas.save();

            //We''re going to scale the X and Y coordinates by the same amount
            canvas.scale(scaleFactor, scaleFactor);

            //If translateX times -1 is lesser than zero, let''s set it to zero. This takes care of the left bound
            if((translateX * -1) < 0) {
               translateX = 0;
            }

            //This is where we take care of the right bound. We compare translateX times -1 to (scaleFactor - 1) * displayWidth.
            //If translateX is greater than that value, then we know that we''ve gone over the bound. So we set the value of 
            //translateX to (1 - scaleFactor) times the display width. Notice that the terms are interchanged; it''s the same
            //as doing -1 * (scaleFactor - 1) * displayWidth
            else if((translateX * -1) > (scaleFactor - 1) * displayWidth) {
               translateX = (1 - scaleFactor) * displayWidth;
            }

            if(translateY * -1 < 0) {
               translateY = 0;
            }

            //We do the exact same thing for the bottom bound, except in this case we use the height of the display
            else if((translateY * -1) > (scaleFactor - 1) * displayHeight) {
               translateY = (1 - scaleFactor) * displayHeight;
            }

            //We need to divide by the scale factor here, otherwise we end up with excessive panning based on our zoom level
            //because the translation amount also gets scaled according to how much we''ve zoomed into the canvas.
            canvas.translate(translateX / scaleFactor, translateY / scaleFactor);

            /* The rest of your canvas-drawing code */
            canvas.restore();
        }

        private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
            @Override
            public boolean onScale(ScaleGestureDetector detector) {
                scaleFactor *= detector.getScaleFactor();
                scaleFactor = Math.max(MIN_ZOOM, Math.min(scaleFactor, MAX_ZOOM));
                return true;
            }
        }
    }