如何检查活动后堆栈中的实例并删除其中一个活动

Question

I have 3 activities , stacked one above another

A -> B -> C -> D

• Now When I am in D , How to find that B is available in backstack
• Now when B is present in back stack remove only B from the stack A,B,C,D
• Then launch B again ... making result to be ACDB

Is this possible in android, How ?

PS: Do I need to post code ?.. let me know ... because there are just activities and no other logic

Answer 1

You can achieve this using ActivityManager. Below is the same code,

ActivityManager m = (ActivityManager) ctx.getSystemService( ctx.ACTIVITY_SERVICE );
List<RunningTaskInfo> runningTaskInfoList =  m.getRunningTasks(10);
Iterator<RunningTaskInfo> itr = runningTaskInfoList.iterator();
while(itr.hasNext()){
    RunningTaskInfo runningTaskInfo = (RunningTaskInfo)itr.next();
    int id = runningTaskInfo.id;
    CharSequence desc= runningTaskInfo.description;
    int numOfActivities = runningTaskInfo.numActivities;
    String topActivity = runningTaskInfo.topActivity.getShortClassName();
}

This will get you all the activities. For more detail, refer docs

https://developer.android.com/reference/android/app/ActivityManager

Answer 2

Problem: Changing the backstack ABCD to ACDB .

Solution: From Android Developer documentation.

FLAG_ACTIVITY_REORDER_TO_FRONT

 public static final int FLAG_ACTIVITY_REORDER_TO_FRONT 

If set in an Intent passed to Context#startActivity, this flag will cause the launched activity to be brought to the front of its task's history stack if it is already running.

For example, consider a task consisting of four activities: A, B, C, D. If D calls startActivity() with an Intent that resolves to the component of activity B, then B will be brought to the front of the history stack, with this resulting order: A, C, D, B. This flag will be ignored if FLAG_ACTIVITY_CLEAR_TOP is also specified.

Answer 3

In Your Base Activity Make an ArrayList of Type Activities.

public static ArrayList<Activity> activityArrayList = new ArrayList<>();

while changing activities just add a line in next activity

BaseActivity.activityArrayList.add(this);

these activities are add in your arrayList, now you can easy add or remove any activity on your choice from array list eg i have create multiple function in Base Activity removing all activities or removing all except main

public static void finishAllExceptMain() {
  try {
    //Constants.logMessage(Constants.TAG, "outer Start Size: " + activityArrayList.size());
    int count = activityArrayList.size();
    while (count > 1) {
      count--;
      activityArrayList.get(count).finish();
      activityArrayList.remove(count);
    }

  } catch (Exception e) {

  }
}

public static void finishLastActivity() {
  int lastActivity = activityArrayList.size() - 1;
  activityArrayList.get(lastActivity).finish();
  activityArrayList.remove(activityArrayList.get(lastActivity));
}