Performance status:
1. Start activityB in activityA, note that there is no finish operation in this process;
2. Finish yourself in activityB;
3. Go back to activityA and find that the original member variables are all cleared/null, and the onCreate method is executed
Expected situation:
It should be that activityA retains the values of all member variables and starts executing from the onStart method
possible reason:
1. The worst case should be that the system memory is full and activityA is forcibly released, but the possibility is relatively low;
2. A very important place that is easily overlooked: Settings -> Developer Options, pull it all the way to the bottom, there is an option " Do not keep activities (destruct each activity after the user leaves) ", here if it is If the wrong operation is selected, it will affect the default life cycle of Android! ! !