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我正在尝试创建一个计时器并在屏幕上显示每个滴答声的计时器。问题是，我得到了一个 javanullexception。

这是我的java代码：

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // requesting to turn the title OFF
    requestWindowFeature(Window.FEATURE_NO_TITLE);

    // making it full screen
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);


    setContentView(R.layout.main);

    timer = (TextView)findViewById(R.id.timer);

     getWindow().setFormat(PixelFormat.UNKNOWN);
     surfaceView = (SurfaceView)findViewById(R.id.camerapreview);
     surfaceHolder = surfaceView.getHolder();  
     surfaceHolder.addCallback(this);
     surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

     controlInflater = LayoutInflater.from(getBaseContext());
     View viewControl = controlInflater.inflate(R.layout.activity_gameplay, null);
     LayoutParams layoutParamsControl
      = new LayoutParams(LayoutParams.FILL_PARENT,
      LayoutParams.FILL_PARENT);
     this.addContentView(viewControl, layoutParamsControl);

     //Create Timer
     new CountDownTimer(60000, 1000) {

         public void onTick(long millisUntilFinished) {
            timer.setText(String.valueOf(millisUntilFinished / 1000));
         }

         public void onFinish() {

         }
         }.start();

}

这是我的 main.xml：

 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 >
<SurfaceView
android:id="@+id/camerapreview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
</LinearLayout>

这是我的 activity_gameplay.xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true">

    <TextView
        android:id="@+id/timer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/lifefull" 
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:text="Timer : "
        android:textSize="20dp"
        android:textColor="#FFFF00" 
        android:textStyle="bold"
        android:layout_marginBottom="10dp"
        android:layout_marginRight="10dp"/>


</LinearLayout>

堆栈跟踪：

01-14 00:57:37.192: E/AndroidRuntime(1235): FATAL EXCEPTION: main
01-14 00:57:37.192: E/AndroidRuntime(1235): java.lang.NullPointerException
01-14 00:57:37.192: E/AndroidRuntime(1235):     at com.example.gems.GamePlay$1.onTick(GamePlay.java:62)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at android.os.CountDownTimer$1.handleMessage(CountDownTimer.java:124)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at android.os.Looper.loop(Looper.java:137)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at android.app.ActivityThread.main(ActivityThread.java:4745)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at java.lang.reflect.Method.invokeNative(Native Method)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at java.lang.reflect.Method.invoke(Method.java:511)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-14 00:57:37.192: E/AndroidRuntime(1235):     at dalvik.system.NativeStart.main(Native Method)

有任何想法吗？

4

1 回答 1

1

您必须从布局膨胀中访问计时器，因为那是它实际所在的位置。

timer = (TextView)viewControl.findViewById(R.id.timer);

所以这条线需要在你膨胀之后。

于 2013-01-13T16:55:10.180 回答