Android提高篇2 之 Service就是后台程序

        上次介绍了Activity以及Intent的使用，这次就介绍Service，如果把Activity比喻为前台程序，那么Service就是后台程序，Service的整个生命周期都只会在后台执行。Service跟Activity一样也由Intent调用。在工程里想要添加一个Service，先新建继承Service的类，然后到AndroidManifest.xml -> Application ->Application Nodes中的Service标签中添加。

         Service要由Activity通过startService 或者 bindService来启动，Intent负责传递参数。先贴出本文程序运行截图：

本文主要讲解Service的调用，以及其生命周期。

上图是startService之后再stopService的Service状态变化。

上图是bindService之后再unbindService的Service状态变化。

       startService与bindService都可以启动Service，那么它们之间有什么区别呢？它们两者的区别就是使Service的周期改变。由startService启动的Service必须要有stopService来结束Service，不调用stopService则会造成Activity结束了而Service还运行着。bindService启动的Service可以由unbindService来结束，也可以在Activity结束之后(onDestroy)自动结束。

 上图是startService之后再Activity.finish()的Service状态变化，Service还在跑着。

上图是bindService之后再Activity.finish()的Service状态变化，Service最后自动unbindService。

main.xml代码：

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<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" android:layout_width="fill_parent" 
    android:layout_height="fill_parent"> 
    <Button android:layout_width="wrap_content" 
        android:layout_height="wrap_content" android:id="@+id/btnStartMyService" 
        android:text="StartMyService"></Button> 
    <Button android:layout_width="wrap_content" 
        android:layout_height="wrap_content" android:id="@+id/btnStopMyService" 
        android:text="StopMyService"></Button> 
    <Button android:layout_width="wrap_content" 
        android:layout_height="wrap_content" android:id="@+id/btnBindMyService" 
        android:text="BindMyService"></Button> 
    <Button android:layout_width="wrap_content" 
        android:layout_height="wrap_content" android:id="@+id/btnUnbindMyService" 
        android:text="UnbindMyService"></Button> 
    <Button android:layout_width="wrap_content" 
        android:layout_height="wrap_content" android:id="@+id/btnExit" 
        android:text="退出程序"></Button> 
</LinearLayout> 
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" android:layout_width="fill_parent"
 android:layout_height="fill_parent">
 <Button android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/btnStartMyService"
  android:text="StartMyService"></Button>
 <Button android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/btnStopMyService"
  android:text="StopMyService"></Button>
 <Button android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/btnBindMyService"
  android:text="BindMyService"></Button>
 <Button android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/btnUnbindMyService"
  android:text="UnbindMyService"></Button>
 <Button android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/btnExit"
  android:text="退出程序"></Button>
</LinearLayout>
 

testService.java的源码：

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package com.testService;  
 
import android.app.Activity;  
import android.app.Service;  
import android.content.ComponentName;  
import android.content.Intent;  
import android.content.ServiceConnection;  
import android.os.Bundle;  
import android.os.IBinder;  
import android.util.Log;  
import android.view.View;  
import android.widget.Button;  
 
public class testService extends Activity {  
    Button btnStartMyService,btnStopMyService,btnBindMyService,btnUnbindMyService,btnExit;  
    @Override 
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        btnStartMyService=(Button)this.findViewById(R.id.btnStartMyService);  
        btnStartMyService.setOnClickListener(new ClickEvent());  
          
        btnStopMyService=(Button)this.findViewById(R.id.btnStopMyService);  
        btnStopMyService.setOnClickListener(new ClickEvent());  
          
        btnBindMyService=(Button)this.findViewById(R.id.btnBindMyService);  
        btnBindMyService.setOnClickListener(new ClickEvent());  
          
        btnUnbindMyService=(Button)this.findViewById(R.id.btnUnbindMyService);  
        btnUnbindMyService.setOnClickListener(new ClickEvent());   
          
        btnExit=(Button)this.findViewById(R.id.btnExit);  
        btnExit.setOnClickListener(new ClickEvent());  
    }  
    @Override 
    public void onDestroy()  
    {  
        super.onDestroy();  
        Log.e("Activity","onDestroy");  
    }  
      
    private ServiceConnection _connection = new ServiceConnection() {    
        @Override 
        public void onServiceConnected(ComponentName arg0, IBinder arg1) {  
            // TODO Auto-generated method stub  
        }  
 
        @Override 
        public void onServiceDisconnected(ComponentName name) {  
            // TODO Auto-generated method stub  
        }    
    };    
    class ClickEvent implements View.OnClickListener{  
 
        @Override 
        public void onClick(View v) {  
            Intent intent=new Intent(testService.this,MyService.class);  
            if(v==btnStartMyService){  
                testService.this.startService(intent);  
            }  
            else if(v==btnStopMyService){  
                testService.this.stopService(intent);  
            }  
            else if(v==btnBindMyService){  
                testService.this.bindService(intent, _connection, Service.BIND_AUTO_CREATE);  
            }  
            else if(v==btnUnbindMyService){  
                if(MyService.ServiceState=="onBind")//Service绑定了之后才能解绑  
                    testService.this.unbindService(_connection);  
            }  
            else if(v==btnExit)  
            {  
                testService.this.finish();  
            }  
              
        }  
          
    }  
} 
package com.testService;

import android.app.Activity;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class testService extends Activity {
    Button btnStartMyService,btnStopMyService,btnBindMyService,btnUnbindMyService,btnExit;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        btnStartMyService=(Button)this.findViewById(R.id.btnStartMyService);
        btnStartMyService.setOnClickListener(new ClickEvent());
       
        btnStopMyService=(Button)this.findViewById(R.id.btnStopMyService);
        btnStopMyService.setOnClickListener(new ClickEvent());
       
        btnBindMyService=(Button)this.findViewById(R.id.btnBindMyService);
        btnBindMyService.setOnClickListener(new ClickEvent());
       
        btnUnbindMyService=(Button)this.findViewById(R.id.btnUnbindMyService);
        btnUnbindMyService.setOnClickListener(new ClickEvent());
       
        btnExit=(Button)this.findViewById(R.id.btnExit);
        btnExit.setOnClickListener(new ClickEvent());
    }
    @Override
    public void onDestroy()
    {
     super.onDestroy();
     Log.e("Activity","onDestroy");
    }
   
    private ServiceConnection _connection = new ServiceConnection() { 
  @Override
  public void onServiceConnected(ComponentName arg0, IBinder arg1) {
   // TODO Auto-generated method stub
  }

  @Override
  public void onServiceDisconnected(ComponentName name) {
   // TODO Auto-generated method stub
  } 
    }; 
    class ClickEvent implements View.OnClickListener{

  @Override
  public void onClick(View v) {
   Intent intent=new Intent(testService.this,MyService.class);
   if(v==btnStartMyService){
    testService.this.startService(intent);
   }
   else if(v==btnStopMyService){
    testService.this.stopService(intent);
   }
   else if(v==btnBindMyService){
    testService.this.bindService(intent, _connection, Service.BIND_AUTO_CREATE);
   }
   else if(v==btnUnbindMyService){
    if(MyService.ServiceState=="onBind")//Service绑定了之后才能解绑
     testService.this.unbindService(_connection);
   }
   else if(v==btnExit)
   {
    testService.this.finish();
   }
   
  }
     
    }
}

MyService.java的源码：

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package com.testService;  
 
import android.app.Service;  
import android.content.Intent;  
import android.os.IBinder;  
import android.util.Log;  
 
public class MyService extends Service {  
    static public String ServiceState="";  
    @Override 
    public IBinder onBind(Intent arg0) {  
        Log.e("Service", "onBind");  
        ServiceState="onBind";  
        return null;  
    }  
    @Override 
    public boolean onUnbind(Intent intent){  
        super.onUnbind(intent);  
        Log.e("Service", "onUnbind");  
        ServiceState="onUnbind";  
        return false;  
          
    }  
    @Override 
    public void onCreate(){  
        super.onCreate();  
        Log.e("Service", "onCreate");  
        ServiceState="onCreate";  
    }  
    @Override 
    public void onDestroy(){  
        super.onDestroy();  
        Log.e("Service", "onDestroy");  
        ServiceState="onDestroy";  
    }  
    @Override 
    public void onStart(Intent intent,int startid){  
        super.onStart(intent, startid);  
        Log.e("Service", "onStart");  
        ServiceState="onStart";  
    }  
 
} 
package com.testService;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {
 static public String ServiceState="";
 @Override
 public IBinder onBind(Intent arg0) {
  Log.e("Service", "onBind");
  ServiceState="onBind";
  return null;
 }
 @Override
 public boolean onUnbind(Intent intent){
  super.onUnbind(intent);
  Log.e("Service", "onUnbind");
  ServiceState="onUnbind";
  return false;
  
 }
 @Override
 public void onCreate(){
  super.onCreate();
  Log.e("Service", "onCreate");
  ServiceState="onCreate";
 }
 @Override
 public void onDestroy(){
  super.onDestroy();
  Log.e("Service", "onDestroy");
  ServiceState="onDestroy";
 }
 @Override
 public void onStart(Intent intent,int startid){
  super.onStart(intent, startid);
  Log.e("Service", "onStart");
  ServiceState="onStart";
 }

}
 

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