Android SurfaceView简例

Android SurfaceView简例

Android中各的SurfaceView和View有很大的不同，两者应用场景不同。大多数View能做的事情SurfaceView也可以，但是SurfaceView效率更高。Android的View绘制过程由Android系统控制，刷新机制开发者比较难以控制。而SurfaceView支持高频、多线程绘制。SurfaceView不存在是否在Android UI主线程绘制问题。通常SurfaceView用于游戏、多媒体（视频）开发。
现在给出一个例子。

写一个自定义的SurfaceView，MySurfaceView.java：

package zhangphil.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

/**
 * Created by Phil on 2017/9/12.
 */

public class MySurfaceView extends SurfaceView {
    public MySurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        SurfaceHolder holder = getHolder();

        final MyTask task = new MyTask(holder);

        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {
                task.startTask();
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
                task.stopTask();
            }
        });
    }

    private class MyTask extends Thread {
        private int width;
        private int height;

        private SurfaceHolder surfaceHolder;
        private Paint paint;
        private float radius = 0;

        public boolean stopTask = false;

        public MyTask(SurfaceHolder surfaceHolder) {
            this.surfaceHolder = surfaceHolder;

            paint = new Paint();
            paint.setAntiAlias(true);
            paint.setColor(Color.RED);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(10f);
        }

        public void startTask() {
            stopTask = false;
            this.start();
        }

        public void stopTask() {
            stopTask = true;
        }

        @Override
        public void run() {
            while (!stopTask) {
                try {
                    Thread.sleep(1);
                } catch (Exception e) {
                    e.printStackTrace();
                }

                Canvas canvas = surfaceHolder.lockCanvas();

                width = getWidth();
                height = getHeight();

                canvas.drawColor(Color.WHITE);
                canvas.drawCircle(width / 2, height / 2, radius++, paint);

                surfaceHolder.unlockCanvasAndPost(canvas);

                //如果半径大于边界，置0.
                if (radius >= (width / 2)) {
                    radius = 0;
                }
            }
        }
    }
}

测试的activity_main.xml：

代码运行结果：