Adding fling gesture to an ImageView

Question

I'm trying to add fling gesture to an imageview. Im using this code

public class MyActivity extends Activity { private void onCreate() { final GestureDetector gdt = new GestureDetector(new GestureListener()); final ImageView imageView = (ImageView) findViewById(R.id.image_view); imageView.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(final View view, final MotionEvent event) { gdt.onTouchEvent(event); return true; } }); } private static final int SWIPE_MIN_DISTANCE = 120; private static final int SWIPE_THRESHOLD_VELOCITY = 200; private class GestureListener extends SimpleOnGestureListener { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { return false; // Right to left } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { return false; // Left to right } if(e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { return false; // Bottom to top } else if (e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { return false; // Top to bottom } return false; } } }

But it just doesn't work. The log says nullpointerexception and it refers to this line imageView.setOnTouchListener(new OnTouchListener() {

Where is my mistake? Am I missing something?

Pragnani Kinnera · Accepted Answer · 2013-02-16 14:30:32Z

1

Your imageView returning null because U haven't setContentView() before actually getting the imageview

setContentView(R.layout.yourlayout) in your onCreate before getting the imageview

answered Feb 16, 2013 at 14:30

Pragnani Kinnera

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Raz Over a year ago

thanks :D the thing is that i added this code before the setcontentview so i just moved it to the top and now it works :)

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