（五）认识Android中的Service

一、使用Service

1.右击java文件夹，选择新建Service，然后重写其中的onStartCommand函数，只要执行了startService函数，onStartCommand便会被执行

package com.example.shiyanshi.learnservice;

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

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        //throw new UnsupportedOperationException("Not yet implemented");

return new Binder(); //要被重写，否则会弹出上面的错误

    }


    //执行startService时被调用
    @Override
    public int

onStartCommand

(Intent intent, int flags, int startId) {
        System.out.println("Service onStartCommand");

        new Thread(new Runnable(){
            @Override
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("******************Service is running********************");
                }
            }

        }).start();
        return super.onStartCommand(intent, flags, startId);
    }

//    @Override
//    public void onCreate() {
//        super.onCreate();
//        System.out.println("**************Service onCreate*****************");
//    }
//
//    @Override
//    public void onDestroy() {
//        super.onDestroy();
//        System.out.println("****************Service onDestroy***************");
//    }

2.启动service时调用startService函数，关闭service时调用stopService函数，该函数需要一个Intent，无论是像下述方式创建intent还是通过

startService(new Intent(MainActivity.this,MyService.class));stopService(new Intent(MainActivity.this,MyService.class));打开或者关闭的服务均是同一个

public class MainActivity extends Activity implements View.OnClickListener, ServiceConnection {
private Intent intent;

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

intent=new Intent(MainActivity.this,MyService.class);

findViewById(R.id.btnStartService).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startService(intent);
}
});

findViewById(R.id.btnStopService).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
stopService(intent);
}
});

二、绑定Service

1.绑定Service时调用bindService函数，public abstract boolean bindService (Intent service, ServiceConnection conn, int flags) 其第二个参数表示服务的连接，服务的连接主要用来侦听服务的状态，可以传递this指针（当传递this时该服务便与当前Activity绑定在一起了，当退出当前Activity时，服务便会自动被系统关闭（调用onDestroy函数，并且会弹出一个错误信息）），第三个参数可以为`BIND_AUTO_CREATE`, `BIND_DEBUG_UNBIND`, `BIND_NOT_FOREGROUND`, `BIND_ABOVE_CLIENT`, `BIND_ALLOW_OOM_MANAGEMENT`, or `BIND_WAIVE_PRIORITY`.注意当第二个参数传递this时，还要在当前Activity类中实现onServiceConnected和onServiceDisconnected，否则会出现类型不匹配的错误，其中onServiceConnected函数在绑定服务成功后执行，onServiceDisconnected服务所在的进程崩溃或被杀掉的时候被执行。

public class MainActivity extends Activity implements View.OnClickListener, ServiceConnection {
    private Intent intent;

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

        intent=new Intent(MainActivity.this,MyService.class);

findViewById(R.id.btnStartService).setOnClickListener(this);
findViewById(R.id.btnStopService).setOnClickListener(this);
findViewById(R.id.btnBindService).setOnClickListener(this);
findViewById(R.id.btnUnbindService).setOnClickListener(this);

    }

 
    @Override
    public void

onClick

(View view) {

switch (view.getId())
{

            case R.id.btnStartService:
                startService(intent);
                break;
            case R.id.btnStopService:
                stopService(intent);
                break;
            case R.id.btnBindService:

bindService(intent, this, Context.BIND_AUTO_CREATE);

                break;
            case R.id.btnUnbindService:

unbindService(this);

                break;
            default:
                break;

}


    }

    //服务被绑定成功成功后执行
    @Override
    public void

onServiceConnected

(ComponentName componentName, IBinder iBinder) {
        System.out.println("***************Service Connect Successful********************");
    }

    //服务所在的进程崩溃或被杀掉的时候被执行
    @Override
    public void

onServiceDisconnected

(ComponentName componentName) {
        System.out.println("***************Service disconnect Successful********************");
    }
}

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
//        throw new UnsupportedOperationException("Not yet implemented");

return new Binder();

    }


    //执行startService时被调用
    @Override
    public int

onStartCommand

(Intent intent, int flags, int startId) {
        System.out.println("Service onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void

onCreate

() {
        super.onCreate();
        System.out.println("**************Service onCreate*****************");
    }

    @Override
    public void

onDestroy

() {
        super.onDestroy();
        System.out.println("****************Service onDestroy***************");
    }
}

2.Service程序

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
//        throw new UnsupportedOperationException("Not yet implemented");

return new Binder();

    }


    //执行startService时被调用
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        System.out.println("Service onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onCreate() {
        super.onCreate();
        System.out.println("**************Service onCreate*****************");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        System.out.println("****************Service onDestroy***************");
    }
}