Question

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android imageView: setting drag and pinch zoom parameters

I am very new to android .. I have an image view in my layout .. I want to enable the zoom in and zoom out for the image coming from this image view .. zoom should be done on two finger touch ..
can anyone tell me how to accomplish this,

Thanks ,

Raj

Answer 1

see this

private static final String TAG = "Touch";

//These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();  

// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
static final int DRAW =3;
int mode = NONE;

// Remember some things for zooming
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

// Limit zoomable/pannable image
private float[] matrixValues = new float[9];
private float maxZoom;
private float minZoom;
private float height;
private float width;
private RectF viewRect;
/////////************ touch events functions **************////////////////////
@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if(hasFocus){  init();   }
}
private void init() {
    maxZoom = 4;
    minZoom = 0.25f;
    height = myimage.getDrawable().getIntrinsicHeight()+20;
    width = myimage.getDrawable().getIntrinsicWidth()+20;
    viewRect = new RectF(0, 0, myimage.getWidth()+20, myimage.getHeight()+20);
}

  /////////************touch events for image Moving, panning and zooming   ***********///
public boolean onTouch(View v, MotionEvent event) {

    // Dump touch event to log
    dumpEvent(event);
    // Handle touch events here...
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
        savedMatrix.set(matrix);
        start.set(event.getX(), event.getY());
        Log.d(TAG, "mode=DRAG");
        mode = DRAG;
        break;
    case MotionEvent.ACTION_POINTER_DOWN:
        oldDist = spacing(event);
        Log.d(TAG, "oldDist=" + oldDist);
        if (oldDist > 10f) {
            savedMatrix.set(matrix);
            midPoint(mid, event);
            mode = ZOOM;
            Log.d(TAG, "mode=ZOOM");
        }
        break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
        mode = NONE;
        Log.d(TAG, "mode=NONE");
        break;
    case MotionEvent.ACTION_MOVE:
        if (mode == DRAW){ onTouchEvent(event);}
        if (mode == DRAG) {
                ///code for draging..        
        } 
     else if (mode == ZOOM) {
         float newDist = spacing(event);
         Log.d(TAG, "newDist=" + newDist);
         if (newDist > 10f) {
             matrix.set(savedMatrix);
             float scale = newDist / oldDist;
             matrix.getValues(matrixValues);
             float currentScale = matrixValues[Matrix.MSCALE_X];
             // limit zoom
             if (scale * currentScale > maxZoom) {
                 scale = maxZoom / currentScale; 
                }else if(scale * currentScale < minZoom){
                    scale = minZoom / currentScale; 
                 }
             matrix.postScale(scale, scale, mid.x, mid.y);
            }
     }
     break;
    }
    myimage.setImageMatrix(matrix);
    return true; // indicate event was handled
}

//*******************Determine the space between the first two fingers
private float spacing(MotionEvent event) {
   float x = event.getX(0) - event.getX(1);
   float y = event.getY(0) - event.getY(1);
   return FloatMath.sqrt(x * x + y * y);
}

//************* Calculate the mid point of the first two fingers 
private void midPoint(PointF point, MotionEvent event) {
   float x = event.getX(0) + event.getX(1);
   float y = event.getY(0) + event.getY(1);
   point.set(x / 2, y / 2);
}
}