Question

我正在研究如何在tabhost活动中绑定服务

我有一个名为Remoteserviceconnection的依赖项目我在tabhost子活动

中调用inokeservice（）

正如我所说，我有一个带有三个子活动的tabhost活动，我想在子活动中绑定一个服务，我得到nul指针异常。

我经历了这两个链接仍然没有得到任何想法

Binding Multiple Activities(Tabs) to a Service using a Base Class Activity

http://code.google.com/p/android/issues/detail?id=2483

我的项目中有4项活动

1）TabBarExample.java 2）FirstTab.java 3）SecondTab.java 4）ThirdTab.java

我究竟做错了什么？

我们非常感谢任何帮助，谢谢

这是我的代码，我在这个java文件中遇到错误，

FirstTab.java

 public class FirstTab extends Activity {
protected static final String TAG = "HvacActivity";
/** Called when the activity is first created. */
private IMyRemoteService remoteService;
private boolean started = false;
private RemoteServiceConnection conn = null;
private Handler serviceHandler;

private static int speed;
private static int hvactemp;
private static int hvacTemppass;
private Task myTask = new Task();
private ImageView fanimgview;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.hvac);

    if(started == false )
    startService();
    bindService();
    System.gc();

    serviceHandler = new Handler();
    serviceHandler.postDelayed(myTask, 1000L);

}

class RemoteServiceConnection implements ServiceConnection {
    // static final int hvactemp = 0;

    public void onServiceConnected(ComponentName className,
            IBinder boundService) {
        remoteService = IMyRemoteService.Stub
                .asInterface((IBinder) boundService);
        Log.d(getClass().getSimpleName(), "onServiceConnected()");
    }

    public void onServiceDisconnected(ComponentName className) {
        remoteService = null;
        // updateServiceStatus();
        Log.d(getClass().getSimpleName(), "onServiceDisconnected");
    }
};

private void startService() {
    if (started) {
        // Toast.makeText(CarHome.this, "Service already started",
        // Toast.LENGTH_SHORT).show();
    } else {
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        startService(i);
        started = true;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "startService()");
    }

}

private void stopService() {
    if (!started) {
        // drivertmpcount.setText(Integer.toString(hvactemp)); //
        // Toast.makeText(CarHome.this, "Service not yet started",
        // Toast.LENGTH_SHORT).show();
    } else {
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        stopService(i);
        started = false;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "stopService()");
    }
}

private void bindService() {
    if (conn == null) {
        conn = new RemoteServiceConnection();
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        bindService(i, conn, Context.BIND_AUTO_CREATE);
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "bindService()");
    } else {
        // Toast.makeText(CarHome.this,
        // "Cannot bind - service already bound",
        // Toast.LENGTH_SHORT).show();
    }
}

private void releaseService() {
    if (conn != null) {
        unbindService(conn);
        conn = null;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "releaseService()");
    } else {
        // Toast.makeText(CarHome.this, "Cannot unbind - service not bound",
        // Toast.LENGTH_SHORT).show();
    }
}

private void invokeService() { // getting ERROR here

    if (conn == null) {
        // Toast.makeText(CarHome.this, "Cannot invoke - service not bound",
        // Toast.LENGTH_SHORT).show();
    } else {
        try {
            System.out.println(remoteService);

            final TextView drivertmpcount = (TextView) findViewById(R.id.curtempcount);
            // final TextView tempcountpass = (TextView)
            // findViewById(R.id.tempcountpass);

            hvactemp = remoteService.getHvacTemp();  // getting ERROR here
            hvacTemppass = remoteService.getHvacTemppass();
            System.out.println("Raghav hvac" + hvactemp);

            System.out.println("jaydeep speed" + speed);
            // rpm_text.setText(rpm);

            drivertmpcount.setText(Integer.toString(hvactemp));
            // tempcountpass.setText(Integer.toString(hvacTemppass));

            Log.d(getClass().getSimpleName(), "invokeService()");
        } catch (RemoteException re) {
            Log.e(getClass().getSimpleName(), "RemoteException");
        }
    }
}

private void updateServiceStatus() {
    String bindStatus = conn == null ? "unbound" : "bound";
    String startStatus = started ? "started" : "not started";
    String statusText = "Service status: " + bindStatus + "," + startStatus;
    // TextView t = (TextView)findViewById( R.id.serviceStatus);
    // t.setText( statusText );
    System.out.println("Jaydeep : " + statusText);
}

protected void onDestroy() {
    super.onDestroy();

    releaseService();
    Log.d(getClass().getSimpleName(), "onDestroy()");
}

class Task implements Runnable {
    public void run() {
        invokeService();  // getting ERROR here

        // serviceHandler.postDelayed(this, 1000L);
        //Log.i(getClass().getSimpleName(),
        //      "Incrementing engineRPM in the run method");
    }

}

}

LOGCAT消息

   09-06 19:12:36.550: E/AndroidRuntime(14116): FATAL EXCEPTION: main
   09-06 19:12:36.550: E/AndroidRuntime(14116): java.lang.NullPointerException
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab.invokeService(FirstTab.java:145)
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab.access$1(FirstTab.java:132)
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab$Task.run(FirstTab.java:180)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Handler.handleCallback(Handler.java:587)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Handler.dispatchMessage(Handler.java:92)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Looper.loop(Looper.java:130)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.app.ActivityThread.main(ActivityThread.java:3686)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at java.lang.reflect.Method.invokeNative(Native Method)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at java.lang.reflect.Method.invoke(Method.java:507)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at dalvik.system.NativeStart.main(Native Method)

Answer 1

此remoteService代码null对象为hvactemp = remoteService.getHvacTemp();。

看起来您期望该服务将在1秒内连接。因为你在调用bindService 1秒后调用invokeService（）。在您的任务中检查remoteService对象是否为空。如果对象不为null，则在对象为invokeService()时调用null方法，然后注册另一个回调，如下所示：

class Task implements Runnable {
    public void run() {
        if(remoteService !=null){
        invokeService();  // getting ERROR here
         } else{
           serviceHandler.postDelayed(this, 1000L);
         }
        //Log.i(getClass().getSimpleName(),
        //      "Incrementing engineRPM in the run method");
    }

}

EDIT1：

或者您可以致电，您可以从invokeService()方法调用onServiceConnected()方法以避免异常

Android：在tabhost类中调用Invokeservice（）时出现空指针异常

1 个答案: