使用SurfaceView时是否需要使用单独的线程？

Question

In Android, I am using a SurfaceView. It is inside a FrameLayout, to draw a couple of things on a transparent layer over the top of a general XML layout (with standard textViews, buttons etc.) The drawing does not involve very intensive computation, and does not animate, it only updates in response to button presses.

All the examples I have seen of SurfaceView use a separate thread for drawing, and then close down that thread in OnSurfaceDestroyed.

My code works without using a separate thread, but it does crash/freeze occasionally, especially when switching between orientations/applications.

So my question is, do I need to use an extra thread to prevent these crashes. And if not, is there any other specific thing I should do in OnSurfaceDestroyed? (I'd rather not post all my code here, just looking for a simple yes/no response and reasons in a couple of sentences).

Answer 1

You don't need to have a separate thread, but it's often a good idea.

For example, take a look at Grafika's " multi-surface test " Activity. It has three overlapping SurfaceViews that are rendered from the UI thread. If you click on the "bounce" button, it starts a new thread to control the animation, because it's simpler to do that way (it can sit in a loop and draw, instead of having to post timed draw events to the UI looper). The bounce thread stops when the Activity is paused. Note the code doesn't do anything in surfaceDestroyed() .

The interaction between SurfaceView and the Activity lifecycle can be tricky. A discussion can be found here .

(It can be tricky to get everything right.)