让Android靠山运行，不用service

今天因项目需求，让Android后台运行，在网上查找了哈资料，找到了一种比较简单的方式，不用service，模拟home键，该代码只能在启动程序中使用，其他activity会报空异常。贴上代码

//后台运行    private void mainservice(){    	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);    }  //后台运行  	 private void startActivitySafely(Intent intent){  		 intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  		 try{  			 startActivity(intent);  		 }catch (ActivityNotFoundException e) {    		        Toast.makeText(this, "未发现该activity",    		                Toast.LENGTH_SHORT).show();    		 } catch (SecurityException e) {    			 Toast.makeText(this, "SecurityException",    		                Toast.LENGTH_SHORT).show();   		 }  	 }

?