java - 4.0 上带有 onTouchListener 和 onClickListener 的 Android TextView NullPointerException

Question

我有一个 TextView，我已经为它分配了一个 onTouchListener 和一个 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 将为手势检测器检测 onFling()。除了 Android 4.0( Ice Cream Sandwich )之外，这段代码没有任何问题。在 4.0 中，我在“_gestureDetector.onTouchEvent(event);”上收到 NullPointerException (当我试图 throw 时)。

但是，如果我注释掉 onClickListener，该 fling 将起作用并且我不会收到 NullPointerException。

我的假设是，如果两个触摸监听器都返回 false，则不会消耗该事件，从而使两者都能正常工作。

有人有什么想法吗？谢谢!

这是我的更多代码:

 /** 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;
    }
}

堆栈跟踪:

 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)

Answer 1

我的 friend ，当你从 gestureDetector 得到你想要处理的事件时，尝试返回 true:

 public boolean onTouch(View v, MotionEvent event) {
     if (_gestureDetector.onTouchEvent(event)) {
         return true;
     }
     return false;
 }

否则返回false。