Android 实现Activity后台运行

 @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
    	if (keyCode == KeyEvent.KEYCODE_BACK) {
    		PackageManager pm = getPackageManager();
    		ResolveInfo homeInfo = pm.resolveActivity(new Intent(Intent.ACTION_MAIN).addCategory(Intent.CATEGORY_HOME), 0);
	    	ActivityInfo ai = homeInfo.activityInfo;
			Intent startIntent = new Intent(Intent.ACTION_MAIN);
			startIntent.addCategory(Intent.CATEGORY_LAUNCHER);
			startIntent.setComponent(new ComponentName(ai.packageName, ai.name));
			startActivitySafely(startIntent);
	    	return true;
    	}
    	return super.onKeyDown(keyCode, event);
    }


 private void startActivitySafely(Intent intent) {  
    	intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  
    	try {  
    		startActivity(intent);  
    	} catch (ActivityNotFoundException e) {  
    		Toast.makeText(this, "没正常启动", Toast.LENGTH_SHORT).show();  
    	} catch (SecurityException e) {  
    		Toast.makeText(this, "存在安全隐患",  
    				Toast.LENGTH_SHORT).show();  
    				Log.e(MYLOG,"Launcher does not have the permission to launch "  
    							+ intent  
    							+ ". Make sure to create a MAIN intent-filter for the corresponding activity "  
    							+ "or use the exported attribute for this activity.",  
    							e);  
    	}  
    }  

 

 

下面是在通知栏开启一个已经启动的Activity

public void createNotification() {
//		int icon = android.R.drawable.ic_menu_revert;
		int icon = R.drawable.icon;
		Notification notification = new Notification(icon, "", notificationId);
		notification.flags = Notification.FLAG_ONLY_ALERT_ONCE;
		notification.setLatestEventInfo(context, "", "", receiveIntent());
		RemoteViews contentView = new RemoteViews(context.getPackageName(), R.layout.app_notification_layout);
		notification.contentView = contentView;
		notfionMgr.notify(notificationId, notification);
	}

	private PendingIntent receiveIntent() {
		Intent appIntent = new Intent(Intent.ACTION_MAIN);
		appIntent.addCategory(Intent.CATEGORY_LAUNCHER);
		appIntent.setComponent(new ComponentName(context.getPackageName(),
				context.getPackageName() + "." + localClassName));
		appIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
		appIntent.setFlags(Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
		appIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
		PendingIntent contentIntent = PendingIntent.getActivity(context, notificationId, appIntent, PendingIntent.FLAG_UPDATE_CURRENT);
		
//		Intent intent = new Intent(context, HomeActivity.class);
////		intent.putExtra(NONE_START_APP, NONE);
//		intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
//		PendingIntent contentIntent = PendingIntent.getActivity(context, notificationId, intent, PendingIntent.FLAG_UPDATE_CURRENT);
		return contentIntent;
	}