Resize ImageView with only one finger movement instead of two

Question

I'm trying to change an ImageView's height with only one finger movement (upside or downside). The code below changes height with two fingers (like pinching or reverse). How can I modify this code to do what I want? Thanks.

public class MainActivity extends Activity {


    private  ImageView iv;
    private  Matrix matrix = new Matrix();
    private float scale = 1f;
    private ScaleGestureDetector SGD;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        iv = iv=(ImageView)findViewById(R.id.imageView);
        SGD = new ScaleGestureDetector(this, new ScaleListener());

    }

    public boolean onTouchEvent(MotionEvent ev) {
        SGD.onTouchEvent(ev);
        return true;
    }

    private class  ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener
    {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            scale *= detector.getScaleFactor();
            scale = Math.max(0.1f, Math.min(scale, 5.0f));

            matrix.setScale(1, scale);
            iv.setImageMatrix(matrix);
            return true;
        }
    }
}

Maybe this helps: https://developer.android.com/training/gestures/movement.html — cherry-wave, Jun 02 '16 at 11:46

HotIceCream · Accepted Answer · 2016-06-04T13:27:43.390

Use GestureDetector for scroll:

@Bind(R.id.container)
ViewGroup container;

@Bind(R.id.image)
ImageView image;
private GestureDetectorCompat detector;
private float yscale = 1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    ButterKnife.bind(this);
    image.setScaleType(ImageView.ScaleType.MATRIX);

    detector = new GestureDetectorCompat(this, new GestureDetector.SimpleOnGestureListener() {

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            Matrix m = new Matrix();
            yscale += distanceY / container.getHeight();
            m.setScale(1, yscale, 0, 0);
            image.setImageMatrix(m);
            return true;
        }
    });
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    return detector.onTouchEvent(event);
} detector.onTouchEvent(event);
}

Thank you for your answer. How can I set a top as fixed and change size from bottom? — jason, Jun 04 '16 at 12:59
Okey I fixed it, thank you, i will give your bounty in 22 hours — jason, Jun 04 '16 at 13:08
Do you know how to set bottom as fixed while resizing? Thanks. — jason, Jun 08 '16 at 13:22

score 0 · Answer 2 · answered Jun 04 '16 at 12:26

change

public boolean onTouchEvent(MotionEvent ev) {
    SGD.onTouchEvent(ev);
    return true;
}

to

public boolean onTouchEvent(MotionEvent ev) {
    switch(ev.getActionMasked()) {
        case MotionEvent.ACTION_DOWN, case MotionEvent.ACTION_UP:
           SGD.onTouchEvent(ev);
           break;
    return true;
}

score -1 · Answer 3 · answered Jun 02 '16 at 11:54

This code snipet should help you to detect up and down

 private VelocityTracker mVelocityTracker = null;
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int index = event.getActionIndex();
        int action = event.getActionMasked();
        int pointerId = event.getPointerId(index);

        switch(action) {
            case MotionEvent.ACTION_DOWN:
                if(mVelocityTracker == null) {
                    // Retrieve a new VelocityTracker object to watch the velocity of a motion.
                    mVelocityTracker = VelocityTracker.obtain();
                }
                else {
                    // Reset the velocity tracker back to its initial state.
                    mVelocityTracker.clear();
                }
                // Add a user's movement to the tracker.
                mVelocityTracker.addMovement(event);
                break;
            case MotionEvent.ACTION_MOVE:
                mVelocityTracker.addMovement(event);
                // When you want to determine the velocity, call 
                // computeCurrentVelocity(). Then call getXVelocity() 
                // and getYVelocity() to retrieve the velocity for each pointer ID. 
                mVelocityTracker.computeCurrentVelocity(1000);
                // Log velocity of pixels per second
                // Best practice to use VelocityTrackerCompat where possible.
                Log.d("", "X velocity: " + 
                        VelocityTrackerCompat.getXVelocity(mVelocityTracker, 
                        pointerId));
                Log.d("", "Y velocity: " + 
                        VelocityTrackerCompat.getYVelocity(mVelocityTracker,
                        pointerId));
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                // Return a VelocityTracker object back to be re-used by others.
                mVelocityTracker.recycle();
                break;
        }
        return true;
    }

Can you help on how to combine this code to my existing code? — jason, Jun 02 '16 at 11:55

Resize ImageView with only one finger movement instead of two

3 Answers3