Android切换前后台点击通知进入当前页面

public class BaseActivity extends AppCompatActivity {
    private static final String TAG = "BaseActivity";
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        AppManager.getInstance().addActivity(this);
    }
    @Override
    protected void onPause() {
        super.onPause();
        if(!isAppOnForeground()){
            Toast.makeText(getApplicationContext(), TAG+"onPause:",
                    Toast.LENGTH_SHORT).show();
        }else {
            Log.e(TAG, "onPause: "+"弹出通知");
            //第一种方式退到后台
            Intent _intent = new Intent(DemoBroadcastReceiver.ACTION_NOTIFY_MESSAGE);
            _intent.setClass(getApplicationContext(), DemoBroadcastReceiver.class);
            sendBroadcast(_intent);
        }
    }

@Override
    public void onActivityStopped(Activity activity) {
        countActivity--;
        L.i("onActivityStopped", "countActivity=" + countActivity);
        if (countActivity <= 0) {
            if (WDRTCSysConfig.getInstance().isCalling()) {
                Intent _intent = new Intent(WDBroadcastReceiver.ACTION_ENABLE_MESSAGES);
                _intent.setClass(getApplicationContext(), WDBroadcastReceiver.class);
                sendBroadcast(_intent);
            }
          
        } 
   }

@Override
    public void onReceive(Context context, Intent intent) {
        switch (intent.getAction()) {
            case ACTION_NOTIFY_MESSAGE:
                String name = null;
                String avatar = null;
                
                //方法一:从系统的Stack中拿到当前的Activity
             /*  ActivityManager mActivityManager = ((ActivityManager) context.getApplicationContext()
                        .getSystemService(Context.ACTIVITY_SERVICE));
                List<ActivityManager.RunningTaskInfo> taskInfos = mActivityManager.getRunningTasks(1);
                Class<?> _class = taskInfos.get(0).topActivity.getClass();
                */
                
                //方法二:从AppManger的Stack中拿到当前的Activity
                Class<?> _class = AppManager.getInstance().currentActivity().getClass();
                if (_class != null) {
                    if (null != reflectionActivity()) {
                        //拿到反射的数据
                        Bundle _bundle = reflectionActivity();
                        if (_bundle != null) {
                            name = _bundle.getString("name");
                            avatar = _bundle.getString("avatar");
                        }
                    }
                    NotificationUtils _notifyUtils = NotificationUtils.getInstance();
                    _notifyUtils.init(context.getApplicationContext(), _class);
                    _notifyUtils.showNotification("从" + name + "退出到后台");
                }
                break;
        }
    }

public void showNotification(@NonNull String contentText){
        PendingIntent _pendingIntent = PendingIntent.getActivity(mContext, notifId, mNotificationIntent,
                PendingIntent.FLAG_UPDATE_CURRENT);
        NotificationCompat.Builder builder = new NotificationCompat.Builder(mContext);
        builder.setLargeIcon(BitmapFactory.decodeResource(mContext.getResources(),R.mipmap.ic_launcher))
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle("通知测试")
                .setContentText(contentText)
                .setSubText(mContext.getString(R.string.notice_click_into))
                .setPriority(Notification.PRIORITY_HIGH)
                .setVibrate(new long[]{0, 0, 0, 10})
                //.setFullScreenIntent(_pendingIntent, true)
                .setContentIntent(_pendingIntent);
        //在什么状态下显示通知,比如锁屏状态
        if (Build.VERSION.SDK_INT >= 21) {
            builder.setVisibility(Notification.VISIBILITY_PUBLIC);
            builder.setCategory(Notification.CATEGORY_MESSAGE);
        }
        mNotification = builder.build();
        mNotificationManager.notify(notifId, mNotification);
    }

public class AppManager {
    private static AppManager instance;
    private static Stack<Activity> activityStack;
    public static AppManager getInstance() {
        if (instance == null) {
            //懒汉双层锁,保证线程安全
            synchronized (AppManager.class) {
                if (instance == null) {
                    instance = new AppManager();
                }
            }
        }
        return instance;
    }
    /**
     * 添加Activity到stack中
     */
    public void addActivity(Activity activity) {
        if (activityStack == null) {
            activityStack = new Stack<>();
        }
        if (activityStack.contains(activity)) {
            activityStack.remove(activity);
        }
        activityStack.add(activity);
    }
    /**
     * 获取stack中当前的Activity
     */
    public Activity currentActivity() {
        if (null != activityStack && null != activityStack.lastElement()) {
            return activityStack.lastElement();
        }
        return null;
    }
    /**
     * 移除当前的Activity
     */
    public void finishActivity() {
        if (null != activityStack && null != activityStack.lastElement()) {
            finishActivity(activityStack.lastElement());
        }
    }
}

 @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        AppManager.getInstance().addActivity(this);
    }

ActivityManager mActivityManager = ((ActivityManager) _app
                .getSystemService(Context.ACTIVITY_SERVICE));
        List<RunningTaskInfo> taskInfos = mActivityManager.getRunningTasks(1);
  Class<?> intentActivity = taskInfos.get(0).topActivity.getClass();