android中的倒计时

我正在尝试创建一个计时器，并在屏幕上显示每个刻度的计时器。问题是,我,；我得到了一个javanullexception

以下是我的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();

}

下面是我的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>

---

有什么想法吗？

您必须从版面膨胀中访问计时器，因为它实际上位于版面膨胀中

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

---

因此，这一行需要在您充气后显示。

哪一行引发异常？完整堆栈跟踪会很有帮助。请参阅我更新的帖子以获取堆栈跟踪再次查看我的帖子。我想有些人会感到困惑，因为我没有发布其他xml。正如@Nicklasgnejserikson所说的，我似乎对这条线路有问题。timer.setText（String.valueOf（millisUntilFinished/1000））；我不知道为什么它不在上面的xml中-您所拥有的只是一个TextView和一个LinearLayout.Ohh。忘了说我正在放大我发布的布局。别介意。它没有给我一个问题。哪个xml是

main

，哪个是

activity\u gameplay

？是啊！谢谢多么简单的错误啊。再次感谢！

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)

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