Android TextView NullPointerException with onTouchListener and onClickListener on Java – 4.0
I have
a TextView to which I have assigned an onTouchListener and an onClickListener:
myTextView.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
_gestureDetector.onTouchEvent(event);
return false;
}
});
myTextView.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Show Toast Notification
}
});
onTouchListener will detect onFling() for gesture detectors. With the exception of Android 4.0 (Ice Cream Sandwich), there is nothing wrong with this code. In 4.0, I wrote in “_gestureDetector.onTouchEvent(event); “I received a NullPointerException (when I tried to throw).
However, if I comment out onClickListener, that fling will work and I won’t get a NullPointerException.
My assumption is that if both touch listeners return false, the event is not consumed, allowing both to work.
Does anyone have any ideas? Thanks!
Here is more of my code :
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.calendar);
_gestureDetector = new GestureDetector(new GestureListener());
}
private class GestureListener extends SimpleOnGestureListener {
@Override
public boolean onDown(MotionEvent e) {
return false;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
if (e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE
&& Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) {
Bottom to top
_calendarTableLayout.removeAllViews();
int month = _calendar.get(Calendar.MONTH);
_calendar.set(Calendar.MONTH, month + 1);
_calendar.set(Calendar.DATE, 1); important
drawCalendar();
return true;
} else if (e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE
&& Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) {
Top to bottom
_calendarTableLayout.removeAllViews();
int month = _calendar.get(Calendar.MONTH);
_calendar.set(Calendar.MONTH, month - 1);
_calendar.set(Calendar.DATE, 1); important
redrawCalendar();
return true;
}
return false;
}
@Override
public void onLongPress(MotionEvent e) {
Do nothing
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
Do nothing
return false;
}
@Override
public void onShowPress(MotionEvent e) {
Do nothing
}
@Override
public boolean onSingleTapUp(MotionEvent e) {
Do nothing
return false;
}
}
Stack trace:
01-27 11:12:16.406: E/AndroidRuntime(1448): FATAL EXCEPTION: main
01-27 11:12:16.406: E/AndroidRuntime(1448): java.lang.NullPointerException
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.GestureDetector.onTouchEvent(GestureDetector.java:587)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.my.package.MyActivity$9.onTouch(MyActivity.java:287)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.View.dispatchTouchEvent(View.java:5481)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1959)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1728)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1892)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1371)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.app.Activity.dispatchTouchEvent(Activity.java:2364)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java: 1840)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.View.dispatchPointerEvent(View.java:5662)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:2863)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.os.Handler.dispatchMessage(Handler.java:99)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.os.Looper.loop(Looper.java:137)
01-27 11:12:16.406: E/AndroidRuntime(1448): at android.app.ActivityThread.main(ActivityThread.java:4340)
01-27 11:12:16.406: E/AndroidRuntime(1448): at java.lang.reflect.Method.invokeNative(Native Method)
01-27 11:12:16.406: E/AndroidRuntime(1448): at java.lang.reflect.Method.invoke(Method.java:511)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-27 11:12:16.406: E/AndroidRuntime(1448): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-27 11:12:16.406: E/AndroidRuntime(1448): at dalvik.system.NativeStart.main(Native Method)
Solution
My friend, when you get the event you want to handle from gestureDetector, try to return true:
public boolean onTouch(View v, MotionEvent event) {
if (_gestureDetector.onTouchEvent(event)) {
return true;
}
return false;
}
Otherwise, false is returned.