Android后台执行的定时器实现

Android后台运行定时器，方便我们运行定位跟踪等任务需求。 以下简要说明实现Android后台定时器的要点， 文章末尾能够下载到project代码，可直接编译运行。

AndroidManifest.xml 文件内容例如以下：

<?
xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.routing.videocamera"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    
    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="16" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.routing.videocamera.Video"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:enabled="true" android:name=".TimerService" /> 
		<receiver android:name=".AutoReceiver" android:label="@string/app_name"> 
			<intent-filter>
			    <action android:name="android.intent.action.BOOT_COMPLETED" />
			    <category android:name="android.intent.category.LAUNCHER" />
			</intent-filter>
		</receiver>
        
    </application>
    
</manifest>

当中关键的代码是赋予项目 RECEIVE_BOOT_COMPLETED 权限 ：

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

Video.java 文件的内容例如以下 ：

package com.routing.videocamera;



public class Video extends Activity {

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

		Intent intent=new Intent(this,AutoReceiver.class);  
		intent.setAction("VIDEO_TIMER"); 
		PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, 0);  
		AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);   
		am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), 10*1000, sender); 
		
		
		Button btnStart = (Button)findViewById(R.id.buttonSave);
		btnStart.setOnClickListener(clickListener);
		
		
		Context ctx = Video.this;       
		SharedPreferences sp = ctx.getSharedPreferences("VIDEO", MODE_PRIVATE);
		//存入数据

		Editor editor = sp.edit();
		
		
		String serverAddr = sp.getString("ServerAddr", "NULL");
		String cameraName = sp.getString("CameraName", "NULL");
		int cameraID   = sp.getInt("CameraID", 0);
		int cameraPort = sp.getInt("CameraPort", 0);

        EditText editServerAddr = (EditText)findViewById(R.id.editServerAddr);  
        editServerAddr.setText(serverAddr);
		
        EditText editCameraName = (EditText)findViewById(R.id.editCameraName);  
        editCameraName.setText(cameraName);
        
        EditText editCameraID = (EditText)findViewById(R.id.editCameraID);  
        editCameraID.setText(Integer.toString(cameraID));
        
        
        EditText editCameraPort = (EditText)findViewById(R.id.editCameraPort);  
        editCameraPort.setText(Integer.toString(cameraPort));
		

	}

	private void saveSetting ()
	{
        EditText editServerAddr = (EditText)findViewById(R.id.editServerAddr);  
        String serverAddr = editServerAddr.getText().toString();
		
        EditText editCameraName = (EditText)findViewById(R.id.editCameraName);  
        String cameraName = editCameraName.getText().toString();
        
        EditText editCameraID = (EditText)findViewById(R.id.editCameraID);  
        int cameraID = Integer.parseInt(editCameraID.getText().toString());
        
        
        EditText editCameraPort = (EditText)findViewById(R.id.editCameraPort);  
        int cameraPort = Integer.parseInt(editCameraPort.getText().toString());
        

		
		//获取SharedPreferences对象
		Context ctx = Video.this;       
		SharedPreferences sp = ctx.getSharedPreferences("VIDEO", MODE_PRIVATE);
		//存入数据
		Editor editor = sp.edit();
		if (serverAddr != "")
			editor.putString("ServerAddr", serverAddr);
		if (cameraName != "")
			editor.putString("CameraName", cameraName);
		
		editor.putInt("CameraID", cameraID);
		
		editor.putInt("CameraPort", cameraPort);

		editor.commit();

        
	}
	

	
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) 
	{
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_video, menu);
		return true;
	}
	
	
	private OnClickListener clickListener = new OnClickListener() 
	{
		
		@Override
		public void onClick(View v) 
		{
			int ret = 0;
			switch(v.getId())
			{
			case R.id.buttonSave:
				saveSetting ();
			break;

			}

		}
	};

}

该文件关键的代码是OnCreate函数中的以下4行代码 ：

		intent.setAction("VIDEO_TIMER"); 
		PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, 0);  
		AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);   
		am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), 10*1000, sender); 

intent.setAction("VIDEO_TIMER") 设置系统向应用程序发送的消息类型为 VIDEO_TIMER。

am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), 10*1000, sender);  该行代码让系统多久发送一次消息，我这里设置的是10秒发送一次VIDEO_TIMER消息。 

发送出去的消息， 会在 class AutoReceiver extends BroadcastReceiver 类里进行接收，并处理。

以下是 TimerService.java 文件 ：

package com.routing.videocamera;


public class TimerService extends Service
{
    public void onCreate() {  

        super.onCreate();  
        Log.v("TimerService",  "OnCreate");
    }  
  
    
    private static String mUrl;
    public void onStart(Intent intent, int startId) {  
    	
    	Log.v("TimerService",  "onStart");    	
       
        
        Context ctx = TimerService.this;  
		//Context ctx = context;       
		SharedPreferences sp = ctx.getSharedPreferences("VIDEO", MODE_PRIVATE);
		//存入数据

		
		String serverAddr = sp.getString("ServerAddr", "");
		String cameraName = sp.getString("CameraName", "");
		int cameraID   = sp.getInt("CameraID", 0);
		int cameraPort = sp.getInt("CameraPort", 0);
        
		if (serverAddr == "" || cameraName == "" || cameraID == 0 || cameraPort == 0 || serverAddr == "NULL" || cameraName == "NULL")
			return;
		
        String Url = serverAddr + "/cameramgr.php?
" + "CameraName=" + cameraName + "&CameraID=" + cameraID + "&CameraPort=" + cameraPort;
        Log.v("FFMPEG URL=",  Url);
        
        mUrl = Url;
         
        
        new Thread() 
        {
        	   @Override
        	   public void run() 
        	   {
        	        HttpParams httpParams;  
        	        // 创建 HttpParams 以用来设置 HTTP 參数（这一部分没必要的）  
        	        httpParams = new BasicHttpParams();  
        	        // 设置连接超时和 Socket 超时，以及 Socket 缓存大小  
        	        HttpConnectionParams.setConnectionTimeout(httpParams, 20 * 1000);  
        	        HttpConnectionParams.setSoTimeout(httpParams, 20 * 1000);  
        	        HttpConnectionParams.setSocketBufferSize(httpParams, 8192);  
        	        // 设置重定向，缺省为 true  
        	        HttpClientParams.setRedirecting(httpParams, true);  
        	        // 设置 user agent  
        	        String userAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2) Gecko/20100115 Firefox/3.6";  
        	        HttpProtocolParams.setUserAgent(httpParams, userAgent);  
        	        // 创建一个 HttpClient 实例  
        	        // 注意 HttpClient httpClient = new HttpClient(); 是Commons HttpClient  
        	        // 中的使用方法，在 Android 1.5 中我们须要使用 Apache 的缺省实现 DefaultHttpClient  
        	        HttpClient httpClient = new DefaultHttpClient(httpParams);  
        	        
        	        //String s = this.getName();
        	        HttpGet httpRequest = new HttpGet(mUrl);  
        	        String strResult = "doGetError";  
        	        try {  
        	            
        	            HttpResponse httpResponse = httpClient.execute(httpRequest);  
        	            
        	            if (httpResponse.getStatusLine().getStatusCode() == 200) 
        	            {  
        	                 
        	                strResult = EntityUtils.toString(httpResponse.getEntity());  
        	            } 
        	            else 
        	            {  
        	                strResult = "Error Response: "  + httpResponse.getStatusLine().toString();  
        	            }  
        	        } 
        	        catch (ClientProtocolException e) 
        	        {  
        	            strResult = e.getMessage().toString();  
        	            e.printStackTrace();  
        	        } 
        	        catch (IOException e)
        	        {  
        	            strResult = e.getMessage().toString();  
        	            e.printStackTrace();  
        	        } 
        	        catch (Exception e)
        	        {  
        	            strResult = e.getMessage().toString();  
        	            e.printStackTrace();  
        	        }  
        	        Log.v("strResult", strResult);  
        	   }
        }.start ();        
    	
    }  
  
   
    public String doPost(String url, List<NameValuePair> params) 
    {  
        /* 建立HTTPPost对象 */  
        HttpPost httpRequest = new HttpPost(url);  
        String strResult = "doPostError";  
        try {  
            /* 加入请求參数到请求对象 */  
            httpRequest.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));  
            /* 发送请求并等待响应 */  
            
	        HttpParams httpParams;  
	        // 创建 HttpParams 以用来设置 HTTP 參数（这一部分没必要的）  
	        httpParams = new BasicHttpParams();  
	        // 设置连接超时和 Socket 超时。以及 Socket 缓存大小  
	        HttpConnectionParams.setConnectionTimeout(httpParams, 20 * 1000);  
	        HttpConnectionParams.setSoTimeout(httpParams, 20 * 1000);  
	        HttpConnectionParams.setSocketBufferSize(httpParams, 8192);  
	        // 设置重定向，缺省为 true  
	        HttpClientParams.setRedirecting(httpParams, true);  
	        // 设置 user agent  
	        String userAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2) Gecko/20100115 Firefox/3.6";  
	        HttpProtocolParams.setUserAgent(httpParams, userAgent);  
	        
            HttpClient httpClient = new DefaultHttpClient(httpParams); 
            HttpResponse httpResponse = httpClient.execute(httpRequest);  
            /* 若状态码为200 ok */  
            if (httpResponse.getStatusLine().getStatusCode() == 200) 
            {  
                /* 读返回数据 */  
                strResult = EntityUtils.toString(httpResponse.getEntity());  
            } 
            else 
            {  
                strResult = "Error Response: "  + httpResponse.getStatusLine().toString();  
            }  
        } 
        catch (ClientProtocolException e) 
        {  
            strResult = e.getMessage().toString();  
            e.printStackTrace();  
        } 
        catch (IOException e)
        {  
            strResult = e.getMessage().toString();  
            e.printStackTrace();  
        } 
        catch (Exception e) 
        {  
            strResult = e.getMessage().toString();  
            e.printStackTrace();  
        }  
        Log.v("strResult", strResult);  
        return strResult;  
    }  
     
    public void onDestroy() {  
        
        super.onDestroy();  
        Log.v("TimerService",  "onDestroy");
    }
	
    public IBinder onBind(Intent intent) {  
        return null;  
    }
    
    public static String inStream2String(InputStream inputStream) 
    {  
        InputStreamReader inputStreamReader = null;  
        try 
        {  
            inputStreamReader = new InputStreamReader(inputStream, "utf8");  
        }
        catch (UnsupportedEncodingException e1) 
        {  
            e1.printStackTrace();  
        }  
        BufferedReader reader = new BufferedReader(inputStreamReader);  
        StringBuffer sb = new StringBuffer("");  
        String line;  
        try
        {  
            while ((line = reader.readLine()) != null) 
            {  
                sb.append(line);  
                sb.append("
");  
            }  
        } 
        catch (IOException e) 
        {  
            e.printStackTrace();  
        }  
        return sb.toString();  
    }   
    
}

该文件是定时器运行的代码，没什么特别的。

以下是 AutoReceiver.java 文件 ：

package com.routing.videocamera;

  

public class AutoReceiver extends BroadcastReceiver
{
    /*要接收的intent源*/
    //static final String ACTION = "android.intent.action.BOOT_COMPLETED";
	private static final int MODE_PRIVATE = 0;
    @Override
    public void onReceive(Context context, Intent intent) 
    {

        if (intent.getAction().equals("VIDEO_TIMER")) 
        {
        	Intent Intentservice = new Intent(context, TimerService.class);  // 要启动的Activity
        	Intentservice.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        	context.startService(Intentservice);
        	

        }
    }
    
    public static String inStream2String(InputStream inputStream) 
    {  
        InputStreamReader inputStreamReader = null;  
        try 
        {  
            inputStreamReader = new InputStreamReader(inputStream, "utf8");  
        }
        catch (UnsupportedEncodingException e1) 
        {  
            e1.printStackTrace();  
        }  
        BufferedReader reader = new BufferedReader(inputStreamReader);  
        StringBuffer sb = new StringBuffer("");  
        String line;  
        try
        {  
            while ((line = reader.readLine()) != null) 
            {  
                sb.append(line);  
                sb.append("
");  
            }  
        } 
        catch (IOException e) 
        {  
            e.printStackTrace();  
        }  
        return sb.toString();  
    }      
    
    public void KeepAlive() 
	{  
		new Thread() 		
		{
			public void run() 	
			{
		        HttpClient client = new DefaultHttpClient();  

		        HttpGet get = new HttpGet("http://www.baidu.com");  
		        HttpResponse response;

		        try {
		        	response = client.execute(get);
			        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) 
			        {  
			            InputStream is = response.getEntity().getContent();  
			            String result = inStream2String(is);  
			            //Assert.assertEquals(result, "GET_SUCCESS");  
			            //Toast.makeText(Video.this, "Http Get Success:", Toast.LENGTH_LONG).show();
			            Log.v("FFMPEG-----= ",  result);
			        }
			        else
			        {
			        	//Toast.makeText(Video.this, "Http Get Fail", Toast.LENGTH_LONG).show();
			        	
			        }
		        }
		        catch (ClientProtocolException e)
		        {
		        	// TODO Auto-generated catch block
		        	e.printStackTrace();
		        } 
		        catch (IOException e)
		        {
		        	// TODO Auto-generated catch block
		        	e.printStackTrace();
		        }
		        //super.run();
			}
        }.start();
    }  
    
    
}

该文件的关键函数是onReceive函数，在这里接收到系统发送出来的 VIDEO_TIMER 消息，然后我们启动一个新任务来运行 TimerService 的代码 ：

    public void onReceive(Context context, Intent intent) 
    {

        if (intent.getAction().equals("VIDEO_TIMER")) 
        {
        	Intent Intentservice = new Intent(context, TimerService.class);  // 要启动的Activity
        	Intentservice.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        	context.startService(Intentservice);
        	

        }
    }

完整源码下载地址 ：http://download.csdn.net/download/langeldep/7845831