Question

我正在尝试使用只需按下按钮即可启动后台服务的应用。然后，后台应用程序应使用套接字打开到服务器的连接，然后发送一些虚拟数据。完成后，服务应该死了。

当我点击按钮并且整个应用程序停止时，我正在获得java.lang.IllegalStateException。这是我迄今为止在主要活动中所拥有的。

public class MainActivity extends AppCompatActivity {

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


  public void start_clicked(View view) {
    Intent my_intent = new Intent(this,BackgroundService.class);
    startActivity(my_intent);
  }
}

以下是与按钮和后台服务对应的XML：这是Activity_Main.xml

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Start"
    android:id="@+id/button"
    android:layout_centerVertical="true"
    android:layout_centerHorizontal="true"
    android:onClick="start_clicked"/>

这是与服务对应的Android清单

<service android:name="com.example.g.backgroundsensor.BackgroundService"
        android:exported="true"
        android:enabled="true" >
</service>

最后这是实际的BackgroundService类（我认为导致错误的片段）

public class BackgroundService extends Service {

private Socket my_socket;

public BackgroundService() {
    try {
        my_socket = new Socket(ip, 5000);
    }catch(Exception e){

    }
}
public int onStartCommand(Intent intent, int flags, int startId) {
    try {
        DataOutputStream my_stream = new DataOutputStream(my_socket.getOutputStream());
        my_stream.write(121);
    }catch(Exception e){

    }
    stopSelf();
    return 1;
}

导致此错误的原因是什么（我将来）自己调试这个错误，因为控制台相对含糊不清：

---/com.example.g.backgroundsensor E/AndroidRuntime: FATAL EXCEPTION: main
---/com.example.g.backgroundsensor E/AndroidRuntime: Process: com.example.g.backgroundsensor, PID: 9876

---/com.example.g.backgroundsensor E/AndroidRuntime: java.lang.IllegalStateException: Could not execute method of the activity

Answer 1

要开始Service，您应该使用startService()而不是startActivity()

Intent my_intent = new Intent(this, BackgroundService.class);
startService(my_intent);

我不知道如何调试它，但你应该总是确定你在调用的地方和你要传递的参数。

Answer 2

首先你必须创建一个Intent Service而不是服务，因为在UI线程上调用了intent服务而且android不允许在UI线程上进行任何网络调用看看下面的代码

public class SocketService extends IntentService {

    @Override
    protected void onHandleIntent(Intent workIntent) {
       //CONNECT SOCKET HERE
    }
}

然后在Manifest中注册此服务

<application>
<service android:name=".SocketService" />
</application>

然后像这样开始你的服务

startService(new Intent(this, SocketService.class)); //YOU HAVE USED startActivity INSTEAD OF startService

Answer 3

我有一个类似的应用程序，我的Manifest只包含这个：

<service android:name=".ServiceActivity" />

在应用程序标记内，就在活动标记之前。除此之外，你的清单应该明确：

<uses-permission android:name="android.permission.INTERNET" />

Answer 4

此代码中存在两个问题。

要启动应该在后台运行的服务，您需要启动服务，因此您需要调用startservice（）：

Intent my_intent = new Intent（this，BackgroundService.class）; startService（my_intent）;
第二大问题是您创建服务的方式。默认情况下，它将在UI线程上启动。因此，在这种情况下，您应该在单独的线程上使用IntentService或服务。

意图服务：

    public class BackgroundService extends IntentService {
        private Socket my_socket;
        @Override
        protected void onHandleIntent(Intent workIntent) {
            try {
                my_socket = new Socket(ip, 5000);
                DataOutputStream my_stream = new DataOutputStream(my_socket.getOutputStream());
                my_stream.write(121);
            }catch(Exception e){

            }
        }
    }

意向服务的主要好处是，一旦完成所有工作并且没有更多请求，它将调用stopSelf。其次，所有工作都将在后台完成。

单独线程上的服务：

    public class BackgroundService extends Service {
      private Looper mServiceLooper;
      private ServiceHandler mServiceHandler;

      // Handler that receives messages from the thread
      private final class ServiceHandler extends Handler {
          public ServiceHandler(Looper looper) {
              super(looper);
          }
          @Override
          public void handleMessage(Message msg) {
              // Normally we would do some work here, like download a file.
              // For our sample, we just sleep for 5 seconds.
              public class HelloService extends Service {
  private Looper mServiceLooper;
  private ServiceHandler mServiceHandler;

  // Handler that receives messages from the thread
  private final class ServiceHandler extends Handler {
      public ServiceHandler(Looper looper) {
          super(looper);
      }
      @Override
      public void handleMessage(Message msg) {
          // Normally we would do some work here, like download a file.
          // For our sample, we just sleep for 5 seconds.
          try {
              Thread.sleep(5000);
          } catch (InterruptedException e) {
              // Restore interrupt status.
              Thread.currentThread().interrupt();
          }
          // Stop the service using the startId, so that we don't stop
          // the service in the middle of handling another job
          stopSelf(msg.arg1);
      }
  }

  @Override
  public void onCreate() {
    // Start up the thread running the service.  Note that we create a
    // separate thread because the service normally runs in the process's
    // main thread, which we don't want to block.  We also make it
    // background priority so CPU-intensive work will not disrupt our UI.
    HandlerThread thread = new HandlerThread("ServiceStartArguments",
            Process.THREAD_PRIORITY_BACKGROUND);
    thread.start();

    // Get the HandlerThread's Looper and use it for our Handler
    mServiceLooper = thread.getLooper();
    mServiceHandler = new ServiceHandler(mServiceLooper);
  }

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
      Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();

      // For each start request, send a message to start a job and deliver the
      // start ID so we know which request we're stopping when we finish the job
      Message msg = mServiceHandler.obtainMessage();
      msg.arg1 = startId;
      mServiceHandler.sendMessage(msg);

      // If we get killed, after returning from here, restart
      return START_STICKY;
  }

  @Override
  public IBinder onBind(Intent intent) {
      // We don't provide binding, so return null
      return null;
  }

  @Override
  public void onDestroy() {
    Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
  }
}
              // Stop the service using the startId, so that we don't stop
              // the service in the middle of handling another job
              stopSelf(msg.arg1);
          }
      }

      @Override
      public void onCreate() {
        // Start up the thread running the service.  Note that we create a
        // separate thread because the service normally runs in the process's
        // main thread, which we don't want to block.  We also make it
        // background priority so CPU-intensive work will not disrupt our UI.
        HandlerThread thread = new HandlerThread("ServiceStartArguments",
                Process.THREAD_PRIORITY_BACKGROUND);
        thread.start();

        // Get the HandlerThread's Looper and use it for our Handler
        mServiceLooper = thread.getLooper();
        mServiceHandler = new ServiceHandler(mServiceLooper);
      }

      @Override
      public int onStartCommand(Intent intent, int flags, int startId) {
          Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();

          // For each start request, send a message to start a job and deliver the
          // start ID so we know which request we're stopping when we finish the job
          Message msg = mServiceHandler.obtainMessage();
          msg.arg1 = startId;
          mServiceHandler.sendMessage(msg);

          // If we get killed, after returning from here, restart
          return START_STICKY;
      }

      @Override
      public IBinder onBind(Intent intent) {
          // We don't provide binding, so return null
          return null;
      }

      @Override
      public void onDestroy() {
        Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
      }
    }

我建议使用intentservice，因为它很简单，非常适合您的场景。

Answer 5

导致此错误的原因

调用

startActivity而不是startService

我怎么能（将来）调试这个，因为控制台相对模糊

这是一个有趣的部分，消息后面应该是一个完整的堆栈跟踪，它是明确描述错误的。像这样：

02-10 12:26:52.734: E/AndroidRuntime(16214): FATAL EXCEPTION: main
02-10 12:26:52.734: E/AndroidRuntime(16214): Process: com.example.sandbox, PID: 16214
02-10 12:26:52.734: E/AndroidRuntime(16214): java.lang.IllegalStateException: Could not execute method for android:onClick
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.view.View$DeclaredOnClickListener.onClick(View.java:4458)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.view.View.performClick(View.java:5204)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.view.View$PerformClick.run(View.java:21153)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.os.Handler.handleCallback(Handler.java:739)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.os.Handler.dispatchMessage(Handler.java:95)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.os.Looper.loop(Looper.java:148)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.ActivityThread.main(ActivityThread.java:5417)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at java.lang.reflect.Method.invoke(Native Method)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
02-10 12:26:52.734: E/AndroidRuntime(16214): Caused by: java.lang.reflect.InvocationTargetException
02-10 12:26:52.734: E/AndroidRuntime(16214):    at java.lang.reflect.Method.invoke(Native Method)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.view.View$DeclaredOnClickListener.onClick(View.java:4453)
02-10 12:26:52.734: E/AndroidRuntime(16214):    ... 9 more
02-10 12:26:52.734: E/AndroidRuntime(16214): Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.sandbox/com.example.sandbox.BackgroundService}; have you declared this activity in your AndroidManifest.xml?
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1794)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Instrumentation.execStartActivity(Instrumentation.java:1512)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Activity.startActivityForResult(Activity.java:3930)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Activity.startActivityForResult(Activity.java:3890)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Activity.startActivity(Activity.java:4213)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at android.app.Activity.startActivity(Activity.java:4181)
02-10 12:26:52.734: E/AndroidRuntime(16214):    at com.example.sandbox.MainActivity.start_clicked(MainActivity.java:19)
02-10 12:26:52.734: E/AndroidRuntime(16214):    ... 11 more

部分Unable to find explicit activity class com.example.sandbox/com.example.sandbox.BackgroundService}; have you declared this activity in your AndroidManifest.xml?非常清晰，只需阅读即可轻松解决问题。

基本后台服务尝试打开套接字

5 个答案: