CODEWITHSUNDEEP
android
aviks
aviks

Reputation: 2097

Surface view drawing thread - busy loop?

All examples of the use of a SurfaceView seems to use a run method that performs a busy loop. Is that a valid way to do this? All the code I can see follows this paradigm from the lunar lander sample. However, creating a busy while loop seems to be a strange way to code multi threaded apps. Shouldnt the drawing code wait on a queue of drawing commands, or something similar. I would have implemented it that way, but the amount of code that I see that does is like below makes me ask the question... What is the best semantics for a thread drawing on a SurfaceView. 

public void run() {
            while (mRun) {
                Canvas c = null;
                try {
                    c = mSurfaceHolder.lockCanvas(null);
                    synchronized (mSurfaceHolder) {
                        // DO DRAWING HERE
                    }
                } finally {

                    if (c != null) {
                        mSurfaceHolder.unlockCanvasAndPost(c);
                    }
                }
            }
        }

Upvotes: 0

Views: 543

Answers (1)

ProjectJourneyman
ProjectJourneyman

Reputation: 3606

I don't know what is best practice in this case, but I have successfully used a slightly modified version of that example in my apps. Since I respond to touch input (rather than continuously updating the canvas) I added a flag to test if drawing even needs to be done. I also added a sleep after each refresh to limit system load. This is my code inside of the try block:

            if(mPanel.needsRefresh()) {
                c = mSurfaceHolder.lockCanvas(null);
                synchronized (mSurfaceHolder) {
                    mPanel.onDraw(c);
                }
            } else {
                SystemClock.sleep(10);
            }

Upvotes: 1

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