[Android] Activity 重複使用

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• Intent intent = new Intent(A.this, B.class);    
• intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT | Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP);

 

Intent.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.

當你依次開啟四個Activity A, B, C, D(沒有finish), 如果在D的時候想startActivity B， 那麼系統會檢測到B已經在task 棧裡， 並且把B提到棧頂,這個過程沒有建立B.

[Android] Activity 重複使用