绑定服务

定义可绑定式使用的服务

定义的服务 是给 与服务所在进程一致的应用 使用的：

public class LocalService extends Service {

    private final IBinder mBinder = new LocalBinder();

    /**
     * 自定义了一个继承Binder类的类
     */
    public class LocalBinder extends Binder {
        LocalService getService() {
            return LocalService.this;
        }
    }

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

    private final Random mGenerator = new Random();

    /**
     * 绑定使用本服务的组件可以通过onBind()方法
     * 返回的LocalBinder对象的getService()方法
     * 获取到本服务实例对象后，使用本getRandomNumber()方法
     */
    public int getRandomNumber() {
        return mGenerator.nextInt(100);
    }
}

多个 与服务所在进程不一样的进程应用 同时使用服务提供的执行操作时，这些执行操作在服务中只会在同一个线程中同步顺序执行：

import android.app.Service;
import android.content.Intent;
import android.os.Build;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;

public class Server extends Service {

    private HandlerThread mHandlerThread;

    private static class MyHandler extends Handler{

        private final static int PRINT_HELLO_WORLD = 1;
        private final static int RECEIVER_MESSENGER = 2;
        private Messenger mClientMessenger;

        MyHandler(HandlerThread handlerThread) {
            super(handlerThread.getLooper());
        }

        @Override
        public void handleMessage(Message msg) {
            // 执行本方法的线程 == Handler对象绑定的线程
            switch (msg.what){
                case PRINT_HELLO_WORLD:
                    System.out.println("Hello World");
                    break;
                case RECEIVER_MESSENGER:
                    // 接收客户端发送过来的Messenger
                    mClientMessenger = msg.replyTo;
                    Message message2 = Message.obtain();
                    message2.what = 3;
                    try {
                        mClientMessenger.send(message2);
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                    break;
            }
        }
    }

    @Override
    public void onCreate() {
        // 创建 接收Handler发送的消息的线程
        mHandlerThread = new HandlerThread("Server");
        mHandlerThread.start();
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public IBinder onBind(Intent intent) {
        Messenger messenger = new Messenger(new MyHandler(mHandlerThread));
        return messenger.getBinder();
    }

    @Override
    public void onDestroy() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            mHandlerThread.quitSafely();
        }else {
            mHandlerThread.quit();
        }
        super.onDestroy();
    }
}

组件使用上述定义的服务

public class LocalActivity extends Activity {

    private ServiceConnection mServiceConnection = null;
    private boolean isBind = false;
    private LocalService mLocalService;

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

        findViewById(R.id.bt_send).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (isBind && mLocalService !=null){
                    int randomNumber = mLocalService.getRandomNumber();
                }
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();

        if (!isBind && mServiceConnection == null){
            Intent intent = new Intent(getApplication(), LocalService.class);
            mServiceConnection = new ServiceConnection() {
                @Override
                public void onServiceConnected(ComponentName name, IBinder service) {
                    Toast.makeText(getApplication(), "成功绑定链接服务", Toast.LENGTH_LONG).show();
                    isBind = true;
                    LocalService.LocalBinder  localBinder = (LocalService.LocalBinder) service;
                    mLocalService = localBinder.getService();
                    mLocalService = null;
                }

                @Override
                public void onServiceDisconnected(ComponentName name) {
                    Toast.makeText(getApplication(), "绑定链接的服务断开了", Toast.LENGTH_LONG).show();
                    isBind = false;
                }
            };
            bindService(intent, mServiceConnection,Context.BIND_AUTO_CREATE);
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (isBind && mServiceConnection != null){
            unbindService(mServiceConnection);
            isBind = false;
            mServiceConnection = null;
            mLocalService = null;
        }
    }
}

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    private ServiceConnection serviceConnection;

    private static class MyHandler extends Handler{

        private final static int PRINT_HE_HE = 3;

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what){
                case PRINT_HE_HE:
                    System.out.println("Hello World");
                    break;
            }
        }
    }

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

        findViewById(R.id.bt_bind).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                intent.setPackage("com.example.zhq.server");
                intent.setAction("com.example.zhq.server.RECEIVER_AND_SEND");
                intent.addCategory("android.intent.category.DEFAULT");
                serviceConnection = new ServiceConnection(){
                    @Override
                    public void onServiceConnected(ComponentName name, IBinder service) {
                        Messenger messenger = new Messenger(service);
                        Message message1 = Message.obtain();
                        message1.what = 1;

                        // 将客户端创建的Messenger发送给服务端
                        Message message2 = Message.obtain();
                        message2.what = 2;
                        message2.replyTo = new Messenger(new MyHandler());
                        try {
                            messenger.send(message1);
                            messenger.send(message2);
                        } catch (RemoteException e) {
                            System.out.println();
                        }
                    }

                    @Override
                    public void onServiceDisconnected(ComponentName name) {
                        System.out.println();
                    }
                };
                bindService(intent,serviceConnection,BIND_AUTO_CREATE);
            }
        });
        findViewById(R.id.bt_unbind).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                unbindService(serviceConnection);
            }
        });
    }
}