什么是保存/加载位图的有效方法

Question

I'm working on an app that can be used for taking notes, simply a drawing application which is keeping bunch of Bitmap objects. I completed creating those pages(Bitmap) and drawing part but i have trouble with memory management, i dynamically create Bitmap object as full screen (for ex; 1280x720) resolution then working on it.

Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)

When user starts to create new pages, normally memory keeps growing. Some point i'm getting "Out of memory" error then my application is crashing.

In my application user can navigate between pages with scrolling and can see maximum two pages at a time (partial pages). I wonder if there any existing API for saving those Bitmap objects which is not displayed at that moment and unload from memory and loading those Bitmap objects when need to display. If there is no existing API can you give me some ideas how can i write my own Memory manager, how i must save those Bitmaps and where ?

For example ; User start to create new pages 1-2-3-4 right now i just need show page4 on the screen i don't need to keep page1-2 (page3 could be in memory for smooth transition ?) in memory i need to save it to disk (or encode as PNG ? or any better solution ? ) When user start to scrolling up that means i need to show page3-page4 at the same time (Maybe i also need to load page2 at this moment to Memory for smooth scrolling), so my app works as like that.

Answer 1

You should use multi threading methods and associate them with async task. Take a look here https://developer.android.com/training/multiple-threads/run-code.html