android 多线程 异步消息处理 服务 学习笔记 （六）

三种多线程编程方法

1     class Mythread extends Thread{
     @Override
     public void run(){}
    }
    new Mythread().start()
2     class Mythread implements Runnable{
        @Override
        public void run(){}
    }
    Mythread myThread=new Mythread();
    new Thread(myThread).start();
3    new Thread{new Runnable{
        @Override
        public void run(){}
    }.start();

异步消息处理机制（使用message更新ui）

public class MainActivity extends Activity implements OnClickListener{
    Button button;
    TextView text;
    public static final int change=1;
    private Handler handler=new Handler(){
        public void handleMessage(Message ms){
            switch(ms.what){
            case change:
                text.setText("nice to meet you");
                break;
                default:
                    break;
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=(Button) findViewById(R.id.change_Button);
        text=(TextView)findViewById(R.id.text);
        button.setOnClickListener(this);
        
    }
    public void onClick(View v){
        switch (v.getId()) {
            case R.id.change_Button:
                new Thread(new Runnable(){
                        public void run(){
                            Message ms=new Message();
                            ms.what=change;
                            handler.sendMessage(ms);
                        }
                        }).start();
                break;
                default:
                    break;
        }
                 
       }
}

使用AsynvTask更新ui

class DownloadTask extends AsyncTask<Void,Integer,Boolean>{
    @Override
    protected void onPreExecute(){
        progressDialog.show();
    }
    @0verride
    protected Boolean doInBackground(Void...params){
        try{
            while(true){
                int downloadPercent=doDownload();
                publishProgress(downloadPercent);
                if(downloadPercent>=100){
                    break;
                }
            }
        }catch(Exception e){
            return false;
            }
            return true;
    }
    protected void onProgressUpdate(Integer...values){
        progressDialog.setMessage("Download"+values[0]+"%");
        }
        @Override 
        protected void onPostExecute(Boolean result){
            progressDialog.dismiss();
            if(result){
                Toast.makeText(context,"Download succeeded",Toast.LENGTH_SHORT).show();
                }else{
                Toast.makeText(context,"Download failed",Toast.LENGTH_SHORT).show();
                }
            }
}

定义一个服务   

 服务定义完成后要使用的话必须同android其他三大组件一样在manifest中注册才行 <service  android:name=".MyService"></service>
 在活动中启动或停止服务的话使用intent
  Intent intent=new Intent(this,Myservice.class);
  startService(intent);
  Intent intent1=new Intent(this,Myservice.class);
  stopService(intent1);或者是在服务的定义中调用stopSelf()来停止服务

public class MyService extends Service{
    public IBinder onBind(Intent intent){
        return null;
        }
    public void onCreate(){
        super.onCreate();
        }
    public int onStartCommand(Intent inten,int flags,int startId){
        return super.onStartCommand(intent,flags,startId);
        }
    public  void onDestroy(){
        super.onDestroy();
        }
}

活动和服务进行通信：使用onBind（）

public class MyService extends Service{
    private DownloadBinder mBinder=new DownloadBinder();
    class DownloadBinder extends Binder{
        public void startDownload(){
            Log.d("MyService","startdownload");
        }
        public int getProgress(){
            Log.d("MyService","getProgress")
            return 0
        }
        }
    public IBinder onBind(Intent intent){
            return mBinder;
        }
}
主活动中调用 先建立一个ServieceConnection匿名类
    private ServiceConnection connection=new ServiceConnection(){
        public void onServiceDisconnected(ComponentName name){}
        public void onServiceConnected(ComponentName name,IBinder service){
            MyService.DownloadBinder downloadBinder=(MyService.DownloadBinder)service;获得一个DownloadBinder实例
            downloadBinder.startDownload();
            downloadBinder.getProgress();
        }
    }
    Intent bindintent=new Intent(this,MyService.class);
    bindService(bindintent,connection,BIND_ANTO_CREATE);绑定服务并且绑定后自动创建
    。。
    unbinderService(connection);解绑，connection为前面定义的ServiceConnection实例
注意服务在任何活动中都是通用的 可以和任何activity 进行绑定

使用intentService（可以自己开启线程并且可以自动停止）
定义：

public class MyIntentService  extends IntentService {

    public MyIntentService( ) {
        super("MyIntentService");
        // TODO Auto-generated constructor stub
    }
    protected void onHandleIntent(Intent intent){
        Log.d("MyIntentService","thread id id"+Thread.currentThread().getId());    
    }
    public void onDestroy(){
        super.onDestroy();
        Log.d("MyIntentService","ondestroy exe");
    }

}
在活动中启动或者的方法是一样的
 Intent intentService=new Intent(this,MyIntentService.class);
 startSercice(intentService);
同样要进行注册注册方法和普通服务一样的

服务的最佳实践  定时循环开启一项服务：

public class LongRunningService extends Service {
     public IBinder onBind(Intent intent){
         return null;
     }
     public int onStartCommand(Intent intent,int flags,int startId){
         new Thread(new Runnable(){
             public void run(){
                 Log.d(".","");
             }
         }).start();
         AlarmManager manager=(AlarmManager)getSystemService(ALARM_SERVICE);
         int anHour=60*60*1000;
         long triggerAtTime=SystemClock.elapsedRealtime()+anHour;
         Intent i=new Intent(this,AlarmReceiver.class);
         PendingIntent pi=PendingIntent.getBroadcast(this,0,i,0);
         manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,triggerAtTime,pi);
         return super.onStartCommand(intent, flags, startId);
         
     }
}

定义一个广播接收器
public class AlarmReceiver extends BroadcastReceiver{
   public void onReceive(Context context,Intent intent){
       Intent i=new Intent(context,LongRunningService.class);
       context.startService(i);
   }
}
在活动中进行启动这个服务 一旦启动就会不断重复 
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent intent=new Intent(this,LongRunningService.class);
        startService(intent);
    }
注意 ：现在的手机当中为了省电，当存在多个Alarm定时任务的时候，他会
把时间相近的几个任务集合在一起去唤醒cpu，所以会有一些时间上的误差，为了准确无误，可以
把服务中manager.set()改为manager.setExact()