详解Android中的Service

public class ExampleService extends Service{
  @Override
  public IBinder onBind(Intent intent) {
    return null;
  }
  @Override
  public void onCreate() {
    super.onCreate();
  }
}

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

// 显示启动ExampleService
Intent intent = new Intent(this,ExampleService.class);
// 启动ExampleService
startService(intent);

  @Override
  public void onDestroy() {
    Log.i("ServiceState","------------------>Destroy");
    super.onDestroy();
  }

//显示关闭Service
Intent serviceIntent = new Intent(MainActivity.this,MyService.class);
//关闭Service
stopService(serviceIntent);

<?xml version="1.0" encoding="utf-8"?>

  
  
  
  
  
  
  
  

package demo.chenqian.com.androidserverdemo;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;
public class MyService extends Service{
　　/* 1、在下方我们定义了内部类MyBinder，这就是为什么我们这里现在能定义binder的原因
　　　　2、这里我们定义binder成员变量的目的是为了在下文的MainActivity中实现转型*/
  private MyBinder binder = new MyBinder();
  @Override
  public void onCreate() {
    Log.d("ServiceInfo","创建成功");
    super.onCreate();
  }
  @Nullable
  @Override
  public IBinder onBind(Intent intent) {
    Log.d("ServiceInfo","绑定成功");
    return null;
  }
  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    Log.d("ServiceInfo","开始执行");
    return super.onStartCommand(intent, flags, startId);
  }
  @Override
  public boolean onUnbind(Intent intent) {
    Log.d("ServiceInfo","解绑成功");
    return super.onUnbind(intent);
  }
  @Override
  public void onDestroy() {
    Log.d("ServiceInfo","销毁成功");
    super.onDestroy();
  }

public void 
onServiceConnected(ComponentName
   name, IBinder service)，注意这里的service是IBinder类型的，我们下方获取MyService将会用到他*/
  class MyBinder extends Binder{
    MyService getService(){
      Log.d("ServiceInfo","成功得到当前服务实例");
      return MyService.this;
    }
  }
}

package demo.chenqian.com.androidserverdemo;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Binder;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
  private Context mContext;
  private Button btnStartService;
  private Button btnStopService;
  private Button btnBindService;
  private Button btnUnbindService;
  private MyService myService;
  private Intent serviceIntent;
  private boolean isBond;
　　/*isBond该变量用来标识当前的Activity与Service是否正在绑定，因为如果不进行标识，如果Activity没有
　　 与Service进行绑定，而执行解除绑定的操作，会照成错误或抛出异常，因为当接触绑定时Android不允许绑定为null */
  /*注意，这里我们新建了一个connection并重写了相关方法，为什么我们要新建这个连接，那是因为在下方的绑定和解绑
   方法即bind和unbind需要一个connection。我们复写相关方法一是为了方便观察，另一个是为了在连接成功或失去关闭
   连接时，执行相关的自定义的任务或操作*/
  private ServiceConnection connection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      Log.d("ServiceState","连接成功");
      myService = ((MyService.MyBinder)service).getService();
    }
    @Override
    public void onServiceDisconnected(ComponentName name) {
      Log.d("ServiceState","关闭连接");
　　　　　　　//当连接指向实例为null没有指引的连接的实例时，好被虚拟机回收，降低占用的资源
      myService = null;
    }
  };
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //初始化数据
    mContext = this;
    isBond = false;
    //引入需要用到的组件
    btnStartService = (Button) findViewById(R.id.btnStartService);
    btnStopService = (Button) findViewById(R.id.btnStopService);
    btnBindService = (Button) findViewById(R.id.btnBindService);
    btnUnbindService = (Button) findViewById(R.id.btnUnbindService);
    //为按钮添加单击事件
    btnStartService.setOnClickListener(this);
    btnStopService.setOnClickListener(this);
    btnBindService.setOnClickListener(this);
    btnUnbindService.setOnClickListener(this);
  }
  @Override
  protected void onStart() {
    serviceIntent = new Intent(this,MyService.class);
    super.onStart();
  }
  @Override
  public void onClick(View v) {
    switch (v.getId()){
      case R.id.btnStartService:
        //开启Service
        startService(serviceIntent);
        break;
      case R.id.btnStopService:
        //关闭Service
        stopService(serviceIntent);
        break;
      case R.id.btnBindService:
        //绑定Service
        isBond = bindService(serviceIntent,connection,Context.BIND_AUTO_CREATE);
        break;
      case R.id.btnUnbindService:
        //解绑Service，当连接为null是解绑会报错
        if(isBond){
          unbindService(connection);
          //如果解绑成功，则修改连接标识为假
          isBond = false;
        }
        break;
    }
  }
}

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