Android后台执行的定时器实现

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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("\n"); } } 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("\n");  
            }  
        } 
        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


















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