按照 Android 开发者网站教程中的说明进行操作时无法绑定到服务

Posted 2023-02-23

【中文标题】按照 Android 开发者网站教程中的说明进行操作时无法绑定到服务

【英文标题】：Can't bind to service when following instructions in tutorial from Android Developers website

【发布时间】：2011-10-19 14:35:45

【问题描述】：

虽然我遵循了 android 开发者网站上的教程，但我无法让我的活动绑定到我的服务。

package com.dieselboris.motioncapture;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.dieselboris.motioncapture.LocalService.LocalBinder;

public class HelloMotionCaptureActivity extends Activity implements OnClickListener 
    private TextView textBox; 
    LocalService mService;
    boolean mBound = false;


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        textBox = (TextView) findViewById(R.id.textView1);  
    

    @Override
    protected void onStart() 
        super.onStart();
        // Bind to LocalService NEVER RETURNS TRUE!!!!
        Intent intent = new Intent(this, LocalService.class);
        boolean isBound = bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
        String text = Boolean.toString(isBound);
        textBox.setText(text);

    

    @Override
    protected void onStop() 
        super.onStop();
        // Unbind from the service
        if (mBound) 
            unbindService(mConnection);
            mBound = false;
        
    

    //start the service when clicked
    public void onClick(View v) 

        if (v == startButton)
           
             //NEVER IN HERE
             if (mBound) 
                int num = mService.getRandomNumber();
                Toast.makeText(this, "incoming number: " + num, Toast.LENGTH_LONG).show();
            
            Toast.makeText(this, "the service should run now", Toast.LENGTH_LONG).show();

        
    

    /** Defines callbacks for service binding, passed to bindService() */
    private ServiceConnection mConnection = new ServiceConnection() 

        @Override
        public void onServiceConnected(ComponentName className,
                IBinder service) 
            // We've bound to LocalService, cast the IBinder and get LocalService instance
            LocalBinder binder = (LocalBinder) service;
            mService = binder.getService();
            mBound = true;
            if (mBound) 
                // Call a method from the LocalService.
                // However, if this call were something that might hang, then this request should
                // occur in a separate thread to avoid slowing down the activity performance.
                int num = mService.getRandomNumber();
                String text = Integer.toString(num);
                textBox.setText(text);
            
        

        @Override
        public void onServiceDisconnected(ComponentName arg0) 
            mBound = false;
        
    ;
 

我尝试连接的服务：

package com.dieselboris.motioncapture;

import java.util.Random;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

public class LocalService extends Service 
    // Binder given to clients
    private final IBinder mBinder = new LocalBinder();
    // Random number generator
    private final Random mGenerator = new Random();

    /**
     * Class used for the client Binder.  Because we know this service always
     * runs in the same process as its clients, we don't need to deal with IPC.
     */
    public class LocalBinder extends Binder 
        LocalService getService() 
            // Return this instance of LocalService so clients can call public methods
            return LocalService.this;
        
    

    @Override
    public IBinder onBind(Intent intent) 
        return mBinder;
    

    /** method for clients */
    public int getRandomNumber() 
      return mGenerator.nextInt(100);
    

我从模拟器得到以下输出：

错误/AndroidRuntime(10878)：致命异常：main 错误/AndroidRuntime(10878)：java.lang.NullPointerException 错误/AndroidRuntime(10878)：在 com.dieselboris.motioncapture.HelloMotionCaptureActivity.onClick(HelloMotionCaptureActivity.java:66) 错误/AndroidRuntime(10878)：在 android.view.View.performClick(View.java:2408) 错误/AndroidRuntime(10878)：在 android.view.View$PerformClick.run(View.java:8817) 错误/AndroidRuntime(10878)：在 android.os.Handler.handleCallback(Handler.java:587) 错误/AndroidRuntime(10878)：在 android.os.Handler.dispatchMessage(Handler.java:92) 错误/AndroidRuntime(10878)：在 android.os.Looper.loop(Looper.java:144) 错误/AndroidRuntime(10878)：在 android.app.ActivityThread.main(ActivityThread.java:4937) 错误/AndroidRuntime(10878)：在 java.lang.reflect.Method.invokeNative(Native Method) 错误/AndroidRuntime(10878)：在 java.lang.reflect.Method.invoke(Method.java:521) 错误/AndroidRuntime(10878)：在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 错误/AndroidRuntime(10878)：在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) ERROR/AndroidRuntime(10878): at dalvik.system.NativeStart.main(Native Method)

似乎我在服务初始化之前调用了公共方法，或者尚未建立连接。

我仔细按照开发者网站上的示例进行操作，无法弄清楚我做错了什么。

【参考方案1】：

我的权限设置不正确。

我必须为整个应用程序插入一个权限，并在应用程序清单中插入一个“uses-permission”。

没有权限，意图永远不会传递给服务。