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POOnFling MotionEvent e1 null?
 

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    <p>Ok. This thing almost drives me crazy.</p> <p>Some days ago I could implement the code below and the toast was successfully called when I tried to swipe right or left. </p> <p>However, now it can't be called, because the e1 is always null! </p> <p>How could this happen? I try this code on the emulator, but a user reports me, that it also doesn't work on real device.</p> <pre><code>public class SwipeGestureListener extends GestureDetector.SimpleOnGestureListener{ private static final int SWIPE_MIN_DISTANCE = 150; private static final int SWIPE_MAX_OFF_PATH = 100; private static final int SWIPE_THRESHOLD_VELOCITY = 100; private final Activity activity; protected MotionEvent mLastOnDownEvent = null; public SwipeGestureListener(Activity activity) { this.activity = activity; } @Override public boolean onDown(MotionEvent e) { mLastOnDownEvent = e; System.out.println(e); return super.onDown(e); } @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { System.out.println(e1 + " " + e2); if (e1==null) e1 = mLastOnDownEvent; if (e1==null || e2==null) return false; float dX = e2.getX()-e1.getX(); float dY = e2.getY()-e1.getY(); if (Math.abs(dY)&lt;SWIPE_MAX_OFF_PATH &amp;&amp; Math.abs(velocityX)&gt;=SWIPE_THRESHOLD_VELOCITY &amp;&amp; Math.abs(dX)&gt;=SWIPE_MIN_DISTANCE ) { if (dX&gt;0) { Toast.makeText(activity.getApplicationContext(), "Right Swipe", Toast.LENGTH_SHORT).show(); activity.fetchPrevious(); } else { Toast.makeText(activity.getApplicationContext(), "Left Swipe", Toast.LENGTH_SHORT).show(); activity.fetchNext(); } return true; } return false; } } </code></pre> <p>The code that implement the gesture:</p> <pre><code>final GestureDetector gdt = new GestureDetector(this, new SwipeGestureListener(this)); listview.setOnTouchListener(new OnTouchListener(){ @Override public boolean onTouch(View v, MotionEvent event) { gdt.onTouchEvent(event); return false; } }); </code></pre>
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