Android 从后台进入前台

public void moveTaskToFront(int taskId, int flags) {

try {
ActivityManagerNative.getDefault().moveTaskToFront(taskId, flags);
} catch (RemoteException e) {
// System dead, we will be dead too soon!

}

 //获取ActivityManager

        ActivityManager mAm = (ActivityManager) context.getSystemService(context.ACTIVITY_SERVICE);

        //获得当前运行的task

        List taskList = mAm.getRunningTasks(100);

        for (ActivityManager.RunningTaskInfo rti : taskList) {

            //找到当前应用的task，并启动task的栈顶activity，达到程序切换到前台

            if(rti.topActivity.getPackageName().equals(context.getPackageName())) {

                mAm.moveTaskToFront(rti.id,0);

                return;

            }

        }

        //若没有找到运行的task，用户结束了task或被系统释放，则重新启动mainactivity

        Intent resultIntent = new Intent(context, MainActivity.class);

        resultIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_SINGLE_TOP);

        context.startActivity(resultIntent);