Android中使用IntentService运行后台任务 _后台任务

知识养成了思想,思想同时又在融化知识。这篇文章主要讲述Android中使用IntentService运行后台任务相关的知识，希望能为你提供帮助。
IntentService提供了一种在后台线程中运行任务的方式，适合处理运行时间较长的后台任务。
长处：
（1）IntentService执行在单独的线程中，不会堵塞UI线程
（2）IntentService不受生命周期的影响
缺点：
（1）不能与UI直接进行交互，能够用Broadcast
（2）顺序运行请求，第二个请求仅仅有在第一个请求运行完以后才干运行
（3）请求不能被中断

使用IntentService的步骤：
（1）在Activity中通过startService启动service，并传递參数。

（2）Service中接收參数，做耗时的处理，处理完成，发送Broadcat。并把处理结果传递出来
（3）Activity中注冊BroadcastReceiver，监听广播。更新UI。

看一个样例：

public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button btn = (Button) this.findViewById(R.id.btn); btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) {//通过startService启动service，并传递參数。 Intent mServiceIntent = new Intent(MainActivity.this,RSSPullService.class); mServiceIntent.setData(Uri.parse(" http://www.baidu.com/" )); MainActivity.this.startService(mServiceIntent); } }); //注冊BroadcastReceiver。监听广播 IntentFilter statusIntentFilter = new IntentFilter(Constants.BROADCAST_ACTION); // Sets the filter' s category to DEFAULT statusIntentFilter.addCategory(Intent.CATEGORY_DEFAULT); DownloadStateReceiver mDownloadStateReceiver = new DownloadStateReceiver(); // Registers the DownloadStateReceiver and its intent filters LocalBroadcastManager.getInstance(this).registerReceiver(mDownloadStateReceiver, statusIntentFilter); } private class DownloadStateReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { String data = https://www.songbingjia.com/android/intent.getStringExtra(Constants.EXTENDED_DATA); Log.e(" test" , data); Toast.makeText(context, data, Toast.LENGTH_SHORT).show(); } }}

public class RSSPullService extends IntentService { public RSSPullService() { super(" RSSPullService" ); } @Override protected void onHandleIntent(Intent workIntent) {//接收參数。做耗时的处理，处理完成。发送Broadcat String localUrlString = workIntent.getDataString(); String data = https://www.songbingjia.com/android/download(localUrlString); Intent localIntent = new Intent(Constants.BROADCAST_ACTION); // Puts the status into the Intent localIntent.putExtra(Constants.EXTENDED_DATA, data); // Broadcasts the Intent to receivers in this app. LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent); } private String download(String localUrlString){ try{ URL url = new URL(localUrlString); HttpURLConnection conn = (HttpURLConnection)url.openConnection(); InputStream in = conn.getInputStream(); ByteArrayOutputStream out = new ByteArrayOutputStream(); byte[] buff = new byte[1024]; int len = 0; while((len = in.read(buff)) != -1){ out.write(buff,0,len); } in.close(); return new String(out.toByteArray()); }catch(Exception e){ e.printStackTrace(); return " " ; } } }

public class Constants { // Defines a custom Intent action public static final String BROADCAST_ACTION = " com.example.android.threadsample.BROADCAST" ; // Defines the key for the status " extra" in an Intent public static final String EXTENDED_DATA_STATUS = " com.example.android.threadsample.STATUS" ; public static final String EXTENDED_DATA = https://www.songbingjia.com/android/" com.example.android.threadsample.DATA" ; }

AndroidManifest.xml:

< manifest xmlns:android=" http://schemas.android.com/apk/res/android" package=" com.example.android.intentservicedemo" android:versionCode=" 1" android:versionName=" 1.0" > < uses-sdk android:minSdkVersion=" 11" android:targetSdkVersion=" 17" /> < !-- Requires this permission to download RSS data from Picasa --> < uses-permission android:name=" android.permission.INTERNET" /> < !-- Defines the application. --> < application android:icon=" @drawable/icon" android:label=" @string/app_name" > < activity android:name=" com.example.android.intentservicedemo.MainActivity" android:label=" @string/activity_title" > < intent-filter> < action android:name=" android.intent.action.MAIN" /> < category android:name=" android.intent.category.LAUNCHER" /> < /intent-filter> < /activity> < !-- No intent filters are specified, so android:exported defaults to " false" . The service is only available to this app. --> < service android:name=" com.example.android.intentservicedemo.RSSPullService" android:exported=" false" /> < /application> < /manifest>

參考：http://developer.android.com/training/run-background-service/index.html
【Android中使用IntentService运行后台任务】