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fedepaol / dragqueen

Sample app that shows android's ViewDragHelper usage
Apache License 2.0
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NPE in ViewDragHelper #1

Open sebnapi opened 9 years ago

sebnapi commented 9 years ago

This happens when the user starts to drag outside of drag-queen-view and continues his move over the drag-queen-view.

05-11 00:58:01.537  29335-29335/com.whiterabbit.dragqueen E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.whiterabbit.dragqueen, PID: 29335
    java.lang.NullPointerException: Attempt to read from null array
            at android.support.v4.widget.ViewDragHelper.shouldInterceptTouchEvent(ViewDragHelper.java:1004)
            at com.whiterabbit.dragqueen.OuterLayout.onInterceptTouchEvent(OuterLayout.java:152)
            at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1960)
            at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
            at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
            at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
            at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
            at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
            at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2369)
            at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1719)
            at android.app.Activity.dispatchTouchEvent(Activity.java:2742)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2330)
            at android.view.View.dispatchPointerEvent(View.java:8666)
            at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4123)
            at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3989)
            at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
            at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
            at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
            at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680)
            at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
            at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737)
            at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
            at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
            at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
            at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
            at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
            at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5807)
            at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5781)
            at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5752)
            at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5897)
            at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
            at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
            at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:176)
            at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:5868)
            at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:5920)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
            at android.view.Choreographer.doCallbacks(Choreographer.java:580)
            at android.view.Choreographer.doFrame(Choreographer.java:548)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
sebnapi commented 9 years ago

ViewDragHelper expects to see the ACTION_DOWN/ACTION_POINTER_DOWN event in shouldInterceptTouchEvent, to set the mInitialMotionX/mInitialMotionY arrays. Through isQueenTarget(event) it can't set the arrays and will crash if it receives the ACTION_MOVE event.

if (isQueenTarget(event)  && mDragHelper.shouldInterceptTouchEvent(event)) {
                return true;
        } else {
            return false;
        }