This setting is usually in the "Security Center-Battery Power and Power Saving Management" of Android phones. Taking Xiaomi mobile phone as an example, the method of closing the lock screen and clearing the memory is as follows:

1, as shown below, found on the mobile phone desktop, and click "Settings":

2. Click "xx Power Supply", as shown in the following figure:

3. Click the gear icon in the upper right corner, as shown in the figure below:

4. As shown in the figure below, click the > arrow behind "Lock screen and clear memory", and then click "Never" in the pop-up menu. After this setting, the phone will not clear the memory after the screen is locked: