Android how to control image to move with in the screen only?

Question

I'm developing an app related to image view rotation, moving and zooming. In this image view rotation and zoom is doing best. when moving image view it is moving but not control and goes to out of screen. How can i control this image view for screen only?

In this i am using Gesture Detectors for image view moving.

Mycode is::

public class MoveGestureDetector extends BaseGestureDetector {

/**
 * Listener which must be implemented which is used by MoveGestureDetector
 * to perform callbacks to any implementing class which is registered to a
 * MoveGestureDetector via the constructor.
 * 
 * @see MoveGestureDetector.SimpleOnMoveGestureListener
 */
public interface OnMoveGestureListener {
    public boolean onMove(MoveGestureDetector detector);
    public boolean onMoveBegin(MoveGestureDetector detector);
    public void onMoveEnd(MoveGestureDetector detector);
}

/**
 * Helper class which may be extended and where the methods may be
 * implemented. This way it is not necessary to implement all methods
 * of OnMoveGestureListener.
 */
public static class SimpleOnMoveGestureListener implements OnMoveGestureListener {
    public boolean onMove(MoveGestureDetector detector) {
        return false;
    }

    public boolean onMoveBegin(MoveGestureDetector detector) {
        return true;
    }

    public void onMoveEnd(MoveGestureDetector detector) {
        // Do nothing, overridden implementation may be used
    }
}

private static final PointF FOCUS_DELTA_ZERO = new PointF();

private final OnMoveGestureListener mListener;

private PointF mCurrFocusInternal;
private PointF mPrevFocusInternal;  
private PointF mFocusExternal = new PointF();
private PointF mFocusDeltaExternal = new PointF();


public MoveGestureDetector(Context context, OnMoveGestureListener listener) {
    super(context);
    mListener = listener;

}

@Override
protected void handleStartProgressEvent(int actionCode, MotionEvent event){
    switch (actionCode) { 
        case MotionEvent.ACTION_DOWN: 
            resetState(); // In case we missed an UP/CANCEL event

            mPrevEvent = MotionEvent.obtain(event);
            mTimeDelta = 0;

            updateStateByEvent(event);
            break;

        case MotionEvent.ACTION_MOVE:
            mGestureInProgress = mListener.onMoveBegin(this);
            break;
    }
}

@Override
protected void handleInProgressEvent(int actionCode, MotionEvent event){    
    switch (actionCode) {
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            mListener.onMoveEnd(this);
            resetState();
            break;

        case MotionEvent.ACTION_MOVE:
            updateStateByEvent(event);

            if (mCurrPressure / mPrevPressure > PRESSURE_THRESHOLD) {
                final boolean updatePrevious = mListener.onMove(this);
                if (updatePrevious) {
                    mPrevEvent.recycle();
                    mPrevEvent = MotionEvent.obtain(event);
                }
            }
            break;
     }
}

protected void updateStateByEvent(MotionEvent curr) {
    super.updateStateByEvent(curr);

    final MotionEvent prev = mPrevEvent;

    // Focus intenal
    mCurrFocusInternal = determineFocalPoint(curr);
    mPrevFocusInternal = determineFocalPoint(prev);

    boolean mSkipNextMoveEvent = prev.getPointerCount() != curr.getPointerCount();
    mFocusDeltaExternal = mSkipNextMoveEvent ? FOCUS_DELTA_ZERO : new PointF(mCurrFocusInternal.x - mPrevFocusInternal.x,  mCurrFocusInternal.y - mPrevFocusInternal.y);

    mFocusExternal.x += mFocusDeltaExternal.x;
    mFocusExternal.y += mFocusDeltaExternal.y;     

}

/**
 * Determine (multi)finger focal point (a.k.a. center point between all
 * fingers)
 * @param MotionEvent e
 * @return PointF focal point
 */
private PointF determineFocalPoint(MotionEvent e){
    final int pCount = e.getPointerCount(); 
    float x = 0f;
    float y = 0f;

    for(int i = 0; i < pCount; i++){
        x += e.getX(i);
        y += e.getY(i);
    }
     return new PointF(x/pCount, y/pCount);
}

public float getFocusX() {
    return mFocusExternal.x;
}

public float getFocusY() {
    return mFocusExternal.y;
}

public PointF getFocusDelta() {
return mFocusDeltaExternal;
}

}

Thanks...

Answer 1

You need to make sure that the following conditions apply when you move your view:

1. the new X > 0
2. the new Y > 0
3. the new X < screenWidth - viewWidth
4. the new Y < screenHeight - viewHeight

Hope this helps :)