SurfaceView使用总结_msurfaceview.addonlayoutchangelistener 回调慢-优快云博客

本文介绍如何使用自定义SurfaceView实现绘图功能，并提供了一个简单的画板示例。SurfaceView允许开发者在子线程中控制绘图速率，适合于需要高性能实时更新的场景。

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SurfaceView与View作用一样都是绘制控件，不同点是View是按照系统速率进行绘制，无法修改，而且是再UI线程中绘制的。而SurfaceView是在子线程中绘制的，可以修改绘制速率。

自定义SurfaceView的用法基本可以套用，基础实现公式是：

1.先创建自定义的View 继承SurfaceView ，实现SurfaceHolder.Callback和Runnable；

2.实现构造方法和接口的方法

3.定义SurfaceHolder，Canvas，isCanvas，Paint；

4.初始化SurfaceHolder、Paint；

5.在surfaceCreated方法中设置isCanvas=true；、开启一个线程；

6.在run方法中判断isCanvas是否为true，进行绘制

7.在绘制过程中获取canvas对象锁定画布，进行canvas绘制，通过try\catch,在finally方法中判断canvas是否为空，不为空进行解除画布锁定

8.在surfaceDestory方法中设置isCanvas=false;

public class MyDrawingBoard extends SurfaceView implements SurfaceHolder.Callback, Runnable {
    private SurfaceHolder mHolder;
    private Canvas mCanvas;
    private boolean isCanvas = false;
    private Paint mPaint;

    public MyDrawingBoard(Context context) {
        super(context);
        init();
    }

    public MyDrawingBoard(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyDrawingBoard(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mHolder = getHolder();
        mHolder.addCallback(this);
        mPaint=new Paint();
        mPaint.setStrokeWidth(3);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.BLUE);
    }

    @Override
    public void surfaceCreated(SurfaceHolder surfaceHolder) {
        isCanvas = true;
        new Thread(this).start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
        isCanvas = false;
    }

    @Override
    public void run() {
        while (isCanvas) {
            draw();
        }
    }

    private void draw() {
        try {
            mCanvas=mHolder.lockCanvas();
            //mCanvas do something 绘制操作
        }catch (Exception e){

        }finally {
            if(mCanvas!=null)
                mHolder.unlockCanvasAndPost(mCanvas);
        }
    }
}

示例：

这是一个实现画板的小例子：

public class MyDrawingBoard extends SurfaceView implements SurfaceHolder.Callback, Runnable {
    private SurfaceHolder mHolder;
    private Canvas mCanvas;
    private boolean isCanvas = false;
    private Path mPath;
    private Paint mPaint;

    public MyDrawingBoard(Context context) {
        super(context);
        init();
    }

    public MyDrawingBoard(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyDrawingBoard(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mHolder = getHolder();
        mHolder.addCallback(this);
        mPath=new Path();
        mPaint=new Paint();
        mPaint.setStrokeWidth(3);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.BLUE);


    }

    @Override
    public void surfaceCreated(SurfaceHolder surfaceHolder) {
        isCanvas = true;
        new Thread(this).start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
        isCanvas = false;
    }

    @Override
    public void run() {
        while (isCanvas) {
            draw();
        }
    }

    private void draw() {
        try {
            mCanvas=mHolder.lockCanvas();
            mCanvas.drawColor(Color.GRAY);
            mCanvas.drawPath(mPath,mPaint);
        }catch (Exception e){

        }finally {
            if(mCanvas!=null)
                mHolder.unlockCanvasAndPost(mCanvas);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x= (int) event.getX();
        int y= (int) event.getY();
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                mPath.moveTo(x,y);
                break;
            case MotionEvent.ACTION_MOVE:
                mPath.lineTo(x,y);
                break;
        }
        return true;
    }
}