day4.23总结_Service绑定和混合模式以及Messager的应用

一、绑定模式的service

绑定模式service相当于在activity端与service端建立了一个长链接(ServiceConnection),然后可以通过此长连接对象中的方法获得Service中返回的绑定对象。通过此对象调用service中的一些业务方法。

 

（1）绑定模式service的生命周期方法:

1)onCreate (只执行一次)

2)onBind(只执行一次)

3)onUnbind(只执行一次)

4)onDestory(只执行一次)

 

我们一般要把自己的业务，在service对象的生命周期方法中实现。

例子1：绑定模式service的生命周期

public class MainActivity extends Activity { private IPlayer player; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);     //绑定service bindService(newIntent(this,MusicService.class),conn,Context.BIND_AUTO_CREATE); } private ServiceConnection conn=new ServiceConnection() {  建立了一个长链接 @Override public void onServiceDisconnected(ComponentName name) { } @Override public void onServiceConnected(ComponentName name, IBinder service) { player=(IPlayer)service;                     返回的绑定对象 } }; public void onPlay(View v){ player.play(); } public void onPause(View v){ player.pause(); }   @Override protected void onDestroy() { super.onDestroy(); //解除绑定 unbindService(conn); } }

public class MusicService extends Service { public MusicService() { } private MediaPlayer mPlayer; @Override public void onCreate() { mPlayer=new MediaPlayer();   创建对象并加载数据 try { mPlayer.setDataSource("/mnt/sdcard/Music/mu01.mp3"); mPlayer.prepare(); } catch (Exception e) { e.printStackTrace(); } } @Override public IBinder onBind(Intent intent) { return new Player();   返回的绑定对象 }   class Player extends Binder implements IPlayer{ @Override public void play() { mPlayer.start(); } @Override public void pause() { mPlayer.pause(); } } @Override public void onDestroy() { if(mPlayer!=null){ mPlayer.release(); mPlayer=null; } } }

 

 

二、混合模式的service

 

混合模式service一般是绑定和启动相结合的一种service应用模式，此应用模式service的生命周期与启动和绑定的顺序相关。

 

（1）混合模式其生命周期相关方法：

1)onCreate

2)onStartCommon (可以执行多次)

3)onBind

4)onUnbind

5)onDestory

例子2：混合模式其生命周期

public class MainActivity extends Activity implements OnClickListener {   Button startBtn,stopBtn,bindBtn,unBindBtn; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);     startBtn=(Button) findViewById(R.id.button1);     bindBtn=(Button) findViewById(R.id.button2);     unBindBtn=(Button) findViewById(R.id.button3);     stopBtn=(Button) findViewById(R.id.button4);          startBtn.setOnClickListener(this);     bindBtn.setOnClickListener(this);     unBindBtn.setOnClickListener(this);     stopBtn.setOnClickListener(this); } private ServiceConnection conn=new ServiceConnection() { @Override public void onServiceDisconnected(ComponentName name) {   } @Override public void onServiceConnected(ComponentName name, IBinder service) {    Log.i("TAG", "onServiceConnected"); } };   @Override public void onClick(View v) { if(v==startBtn){  startService(new Intent(this,MyService01.class)); }else if(v==bindBtn){  bindService(new Intent(this,MyService01.class),  conn, Context.BIND_AUTO_CREATE); }else if(v==unBindBtn){  unbindService(conn); }else if(v==stopBtn){  stopService(new Intent(this,MyService01.class)); } } }

public class MyService01 extends Service { public MyService01() { }   @Override public void onCreate() { Log.i("TAG", "onCreate"); }   @Override public IBinder onBind(Intent intent) { Log.i("TAG", "onBind"); return new Binder(); }   @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.i("TAG", "onStartCommand"); return super.onStartCommand(intent, flags, startId); }   @Override public boolean onUnbind(Intent intent) { Log.i("TAG", "onUnbind"); return true; }   @Override public void onDestroy() { Log.i("TAG", "onDestroy"); } }

 

三、 Messenger对象的应用

（1）概述

Messenger 对象可以实现跨进程之间的消息传递，它可以实现在service与activity之间的通讯，底层需要封装对应的一个handler对象。

（2）相关方法

1)Messenger(binder) :绑定成功以后在connection中应用

2)Messenger(handler):replyTo

3)send(message):

例子3：Messenger 对象可以实现跨进程之间的消息传递

public class MainActivity extends Activity {   @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);   bindService(new Intent(this,MyService01.class), conn, Context.BIND_AUTO_CREATE);(1)启动服务 }   private Handler aHandler=new Handler(){ public void handleMessage(Message msg) { Log.i("TAG",String.valueOf(msg.obj));(9)处理service传过来的msg }; }; private ServiceConnection conn=new ServiceConnection() { @Override public void onServiceDisconnected(ComponentName name) { }   @Override public void onServiceConnected(ComponentName name, IBinder binder) {   Messenger mGer=new Messenger(binder);(3)创建一个返回来binder的Messenger Message msg=Message.obtain(); msg.obj="hello service!"; msg.replyTo=new Messenger(aHandler);(4)创建绑定aHandler的Messenger赋值给message try{ mGer.send(msg);//发送消息(5) }catch(Exception e){} } }; protected void onDestroy() { super.onDestroy(); unbindService(conn); }; }

public class MyService01 extends Service { public MyService01() { } private Handler bhandler=new Handler(){ public void handleMessage(Message msg) {(6)处理activity传过来的msg  Log.i("TAG",String.valueOf(msg.obj));  //可以回复消息给activity  Message aMsg=Message.obtain();(7)创建一个msg  aMsg.obj="hello activity";  try{  msg.replyTo.send(aMsg);(8)发送消息  }catch(Exception e){e.printStackTrace();} }; }; @Override public IBinder onBind(Intent intent) { Log.i("TAG", "onBind"); return new Messenger(bhandler).getBinder();(2)返回IBinder } }

 

例子4：Messenger对象的应用：更新音乐列表

ublic class MainActivity extends ListActivity {   private SimpleCursorAdapter adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.activity_main);     adapter=new SimpleCursorAdapter(this,     android.R.layout.simple_list_item_2,     null, new String[]{Media.TITLE,Media.ARTIST},     new int[]{android.R.id.text1,android.R.id.text2},     CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);     setListAdapter(adapter);     startService(new Intent(this,MusicService.class));     bindService(new Intent(this,MusicService.class),         conn, Context.BIND_AUTO_CREATE); } private Handler aHandler=new Handler(){ public void handleMessage(Message msg) { Cursor cursor=MusicService.getCursor(); adapter.changeCursor(cursor); }; }; private ServiceConnection conn=new ServiceConnection() { @Override public void onServiceDisconnected(ComponentName name) { } @Override public void onServiceConnected(ComponentName name, IBinder binder){    //时机不合适 Message msg=Message.obtain(); msg.replyTo=new Messenger(aHandler); try{     new Messenger(binder).send(msg); }catch(Exception e){} } }; protected void onListItemClick(android.widget.ListView l, View v, int position, long id) { Intent intent=new Intent("ACTION_PLAY"); intent.putExtra("position", position); startService(intent); }; @Override protected void onDestroy() { super.onDestroy(); stopService(new Intent(this,MusicService.class)); }

public class MusicService extends Service { public MusicService() {} @Override public void onCreate() { new MusicAsyncTask().execute(); } private Messenger replyTo; private Handler sHandler=new Handler(){ public void handleMessage(Message msg) { replyTo=msg.replyTo; }; }; @Override public IBinder onBind(Intent intent) {   return new Messenger(sHandler).getBinder(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { if(intent!=null){ String action=intent.getAction(); if("ACTION_PLAY".equals(action)){  int pos=intent.getIntExtra("position",0);  playMusic(pos); }//else if() } return START_STICKY; } private MediaPlayer mPlayer; public void playMusic(int pos){ if(mPlayer==null){ mPlayer=new MediaPlayer(); } mPlayer.reset(); try{ cursor.moveToPosition(pos); String path=cursor.getString(cursor.getColumnIndex(Media.DATA)); mPlayer.setDataSource(path); mPlayer.prepare(); mPlayer.start(); }catch(Exception e){e.printStackTrace();}; } class MusicAsyncTask extends AsyncTask<Void, Void, Cursor>{ @Override protected Cursor doInBackground(Void... params) { return getContentResolver() .query(Media.EXTERNAL_CONTENT_URI, null,Media.IS_MUSIC+"=1", null,null); } @Override protected void onPostExecute(Cursor cursor) { //将数据如何更新到activity对应的页面上     MusicService.cursor=cursor;     //??????通知activity调用getCursor执行更新动作     while(replyTo==null);     try{     replyTo.send(Message.obtain());     }catch(Exception e){} } } private static Cursor cursor; /**什么时候调用此方法更新UI*/ public static Cursor getCursor() { return cursor; } }