23

我用 Toast 来发出通知，但它似乎会出现，即使它的活动不在当前屏幕中并且已经启动了一些其他活动。

我想检查这种情况，当活动不是当前活动时，我不会发送 Toast 通知。但是怎么办？

4

7 回答 7

86

当您的 Activity 进入前台时，onResume()将调用其方法。当另一个 Activity 出现在您的 Activity 前面时，onPause()将调用它的方法。因此，您需要做的就是实现一个布尔值，指示您的 Activity 是否在前台：

private boolean isInFront;

@Override
public void onResume() {
    super.onResume();
    isInFront = true;
}

@Override
public void onPause() {
    super.onPause();
    isInFront = false;
}
于 2010-07-16T05:41:46.833 回答
7 
ArrayList<String> runningactivities = new ArrayList<String>();

ActivityManager activityManager = (ActivityManager)getBaseContext().getSystemService (Context.ACTIVITY_SERVICE); 

List<RunningTaskInfo> services = activityManager.getRunningTasks(Integer.MAX_VALUE); 

for (int i1 = 0; i1 < services.size(); i1++) { 
    runningactivities.add(0,services.get(i1).topActivity.toString());  
} 

if(runningactivities.contains("ComponentInfo{com.app/com.app.main.MyActivity}")==true){
    Toast.makeText(getBaseContext(),"Activity is in foreground, active",1000).show(); 
}

这样，您将知道指向的活动是否是当前可见活动。

于 2012-01-22T19:23:17.823 回答
5

我不喜欢自己处理状态，所以我实现了一个为我做这件事的类。

package mypackage;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

// Mine extends AppCompatActivity - your's might need to extend Activity, depending on whether
// you use the support library or not.
public class StateTrackingActivity extends AppCompatActivity {

    public enum ActivityState {

        CREATED, RESUMED, STARTED, PAUSED, STOPPED, DESTROYED
    }

    private ActivityState _activityState;

    protected ActivityState getActivityState() { return _activityState; }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        _activityState = ActivityState.CREATED;
    }

    @Override
    protected void onResume() {

        super.onResume();
        _activityState = ActivityState.RESUMED;
    }

    @Override
    protected void onStart() {

        super.onStart();
        _activityState = ActivityState.STARTED;
    }

    @Override
    protected void onPause() {

        super.onPause();
        _activityState = ActivityState.PAUSED;
    }

    @Override
    protected void onStop() {

        super.onStop();
        _activityState = ActivityState.STOPPED;
    }

    @Override
    protected void onDestroy() {

        super.onDestroy();
        _activityState = ActivityState.DESTROYED;
    }
}

然后你的活动可以扩展这个，你可以通过调用来获取状态getActivityState()。

于 2016-07-10T09:10:24.030 回答
3

这是我的终极 isActivityVisible 功能。

protected boolean isActivityVisible() {
    if (this.mActivity != null) {
        Class klass = this.mActivity.getClass();
        while (klass != null) {
            try {
                Field field = klass.getDeclaredField("mResumed");
                field.setAccessible(true);
                Object obj = field.get(this.mActivity);
                return (Boolean)obj;
            } catch (NoSuchFieldException exception1) {
//                Log.e(TAG, exception1.toString());
            } catch (IllegalAccessException exception2) {
//                Log.e(TAG, exception2.toString());
            }
            klass = klass.getSuperclass();
        }
    }
    return false;
}
于 2014-07-09T15:03:23.570 回答
2 
if (BaseActivity.this instanceof Faq)
            {
                Toast.makeText(BaseActivity.this, "You are in the Same Page", Toast.LENGTH_SHORT).show();
            }else {
                Intent intent = new Intent(BaseActivity.this, Faq.class);
                startActivity(intent);
                drawer.closeDrawer(GravityCompat.START);
            }

//// 这里是我所有的活动都在名为 BaseActivity 的活动上扩展

于 2016-11-02T06:42:52.763 回答
-1

有Activity#isTaskRoot()方法

于 2011-06-08T08:45:06.047 回答
-5 
  if ( getActivity() instanceof ManageCardActivity){

   // your code
  }
于 2017-03-09T06:44:17.477 回答