1

我/我有一个 NullPointerException，我相信这个问题与 onCreate 方法中的 setContentView 有关。

这是主要活动：

protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

这是我将文本添加到 textView 的代码。这段代码是在另一个视图中编写的：

public boolean onTouchEvent(MotionEvent event) {

    // get pointer index from the event object
    int pointerIndex = event.getActionIndex();

    // get pointer ID
    int pointerId = event.getPointerId(pointerIndex);

    // get masked (not specific to a pointer) action
    int maskedAction = event.getActionMasked();

    switch (maskedAction) {

    case MotionEvent.ACTION_DOWN:
    case MotionEvent.ACTION_POINTER_DOWN: {
        // We have a new pointer. Lets add it to the list of pointers

        PointF f = new PointF();
        f.x = event.getX(pointerIndex);
        f.y = event.getY(pointerIndex);
        mActivePointers.put(pointerId, f);
        break;
    }
    case MotionEvent.ACTION_MOVE: { // a pointer was moved
        for (int size = event.getPointerCount(), i = 0; i < size; i++) {
            PointF point = mActivePointers.get(event.getPointerId(i));
            if (point != null) {
                point.x = event.getX(i);
                point.y = event.getY(i);
            }
        }
        break;
    }
    case MotionEvent.ACTION_UP:
        String schema = getLetterSchema();
        String letter = getLetter(schema);

        if(letter == null) {
            System.out.println("***************************");
            System.out.println("****ERROR***"+schema+"***");
            System.out.println("***************************");
        } else {

            TextView t=(TextView)findViewById(R.id.textView);
            t.setText(letter);

            System.out.println("***************************");
            System.out.println("*"+letter+"*");
            System.out.println("****************"+schema+"****");
        }

        mActivePointers.clear();
        break;
    case MotionEvent.ACTION_POINTER_UP:
        // DO NOT USE
        break;
    case MotionEvent.ACTION_CANCEL: {
        // DO NOT USE
        mActivePointers.clear();
        break;
    }
    }
    ;
    invalidate();

    return true;
}

这是日志：

09-09 18:01:47.221: I/(29842): PLATFORM VERSION : JB-MR-2
09-09 18:01:47.246: D/mali_winsys(29842): new_window_surface returns 0x3000
09-09 18:01:47.321: D/OpenGLRenderer(29842): Enabling debug mode 0
09-09 18:01:50.546: E/InputEventReceiver(29842): Exception dispatching input event.
09-09 18:01:50.551: E/MessageQueue-JNI(29842): Exception in MessageQueue callback:      handleReceiveCallback
09-09 18:01:50.556: E/MessageQueue-JNI(29842): java.lang.NullPointerException
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.example.multitouch.MultitouchView.onTouchEvent(MultitouchView.java:127)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.View.dispatchTouchEvent(View.java:8112)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2252)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1587)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.app.Activity.dispatchTouchEvent(Activity.java:2507)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2200)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.View.dispatchPointerEvent(View.java:8320)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4558)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4430)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4042)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4011)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4122)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4019)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4179)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4042)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4011)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4019)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6333)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6249)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6220)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6185)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6413)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.os.MessageQueue.nativePollOnce(Native Method)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.os.MessageQueue.next(MessageQueue.java:138)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.os.Looper.loop(Looper.java:123)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at android.app.ActivityThread.main(ActivityThread.java:5335)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at java.lang.reflect.Method.invokeNative(Native Method)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at java.lang.reflect.Method.invoke(Method.java:515)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
09-09 18:01:50.556: E/MessageQueue-JNI(29842):  at dalvik.system.NativeStart.main(Native Method)
09-09 18:01:50.556: D/AndroidRuntime(29842): Shutting down VM
09-09 18:01:50.556: W/dalvikvm(29842): threadid=1: thread exiting with uncaught exception (group=0x4175fc08)
09-09 18:01:50.571: E/AndroidRuntime(29842): FATAL EXCEPTION: main
09-09 18:01:50.571: E/AndroidRuntime(29842): Process: com.example.multitouch, PID: 29842
09-09 18:01:50.571: E/AndroidRuntime(29842): java.lang.NullPointerException
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.example.multitouch.MultitouchView.onTouchEvent(MultitouchView.java:127)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.View.dispatchTouchEvent(View.java:8112)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2420)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2153)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2252)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1587)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.app.Activity.dispatchTouchEvent(Activity.java:2507)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2200)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.View.dispatchPointerEvent(View.java:8320)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4558)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at    android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4430)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4042)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4011)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4122)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4019)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4179)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4042)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4011)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4019)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3988)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6333)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6249)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6220)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6185)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6413)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.os.MessageQueue.nativePollOnce(Native Method)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.os.MessageQueue.next(MessageQueue.java:138)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.os.Looper.loop(Looper.java:123)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at android.app.ActivityThread.main(ActivityThread.java:5335)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at java.lang.reflect.Method.invokeNative(Native Method)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at java.lang.reflect.Method.invoke(Method.java:515)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
09-09 18:01:50.571: E/AndroidRuntime(29842):    at dalvik.system.NativeStart.main(Native Method)
09-09 18:01:53.381: I/Process(29842): Sending signal. PID: 29842 SIG: 9

第 127 行是这样的：t.setText(letter);

这是主要活动：

public class MainActivity extends Activity 
{

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);     

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) 
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}
4

1 回答 1

0

你的假设是错误的。它与 无关setContentView()，而是与您的findViewById电话有关。您声明代码来自另一个视图，这意味着您的代码在扩展的类中View。但View它本身也有findViewById()方法。在文档下方

查找具有给定 id 的子视图。如果此视图具有给定的 id，则返回此视图。

参数：
id 要搜索的 id。
返回：
在层次结构中具有给定 id 的视图或 null

而且我猜你R.id.textView不是你另一个观点的孩子。

你想调用findViewById()你的Context，例如调用getContext().findViewById(R.id.textView). 希望有帮助。

于 2014-09-09T19:08:10.123 回答