Android HandlerCallback.handlerMessage 归属线程

Answer 1

The logic inside

1, Show and handleMessage is not in the main thread.
2. ImageSize=0 is output at other points because your Show has not yet called back and the image has not been downloaded.
3. When handleMessage is executed, the thread it is on is the thread where the new Handler() passed in when you Looper is located (you used HandlerThread), so in the entire logic of handleMessage, there is no other code. Possibility of main thread execution.