SurfaceView介绍

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1.SurfaceView与View的区别

View主要适用于主动更新的情况，而SurfaceView主要适用于被动更新，例如频繁刷新。
View在主线程中对画面进行刷新，而SurfaceView通常会通过一个子线程对画面进行更新。
View在绘图时没有使用双缓冲机制，而SurfaceView在底层实现机制中就已经实现了双缓冲机制。

2.SurfaceView的使用

创建SurfaceView，需要实现两个接口：SurfaceHolder.Callback和Runnable
初始化SurfaceView,初始化SurfaceHolder并注册其回调方法
使用SurfaceView，在surfaceCreated（）方法中开启子线程进行绘制

SurfaceView的代码模板：

package com.imooc.surfaceviewtest;import android.content.Context;import android.graphics.Canvas;import android.util.AttributeSet;import android.view.SurfaceHolder;import android.view.SurfaceView;public class SurfaceViewTemplate extends SurfaceView        implements SurfaceHolder.Callback, Runnable {    // SurfaceHolder    private SurfaceHolder mHolder;    // 用于绘图的Canvas    private Canvas mCanvas;    // 子线程标志位    private boolean mIsDrawing;    public SurfaceViewTemplate(Context context) {        super(context);        initView();    }    public SurfaceViewTemplate(Context context, AttributeSet attrs) {        super(context, attrs);        initView();    }    public SurfaceViewTemplate(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        initView();    }    private void initView() {        mHolder = getHolder();        mHolder.addCallback(this);        setFocusable(true);        setFocusableInTouchMode(true);        this.setKeepScreenOn(true);        //mHolder.setFormat(PixelFormat.OPAQUE);    }    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing = true;        new Thread(this).start();    }    @Override    public void surfaceChanged(SurfaceHolder holder,                               int format, int width, int height) {    }    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mIsDrawing = false;    }    @Override    public void run() {        while (mIsDrawing) {            draw();        }    }    private void draw() {        try {            mCanvas = mHolder.lockCanvas();//获得当前的Canvas绘图对象            // draw sth        } catch (Exception e) {        } finally {            if (mCanvas != null)            //对画布内容进行提交                mHolder.unlockCanvasAndPost(mCanvas);        }    }}

3.SurfaceView的使用实例

绘制正弦曲线
代码如下：

public class SinView extends SurfaceView        implements SurfaceHolder.Callback, Runnable {    private SurfaceHolder mHolder;    private Canvas mCanvas;    private boolean mIsDrawing;    private int x = 0;    private int y = 0;    private Path mPath;    private Paint mPaint;    public SinView(Context context) {        super(context);        initView();    }    public SinView(Context context, AttributeSet attrs) {        super(context, attrs);        initView();    }    public SinView(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        initView();    }    private void initView() {        mHolder = getHolder();        mHolder.addCallback(this);        setFocusable(true);        setFocusableInTouchMode(true);        this.setKeepScreenOn(true);        mPath = new Path();        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mPaint.setColor(Color.RED);        mPaint.setStyle(Paint.Style.STROKE);        mPaint.setStrokeWidth(10);        mPaint.setStrokeCap(Paint.Cap.ROUND);        mPaint.setStrokeJoin(Paint.Join.ROUND);    }    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing = true;        mPath.moveTo(0, 400);        new Thread(this).start();    }    @Override    public void surfaceChanged(SurfaceHolder holder,                               int format, int width, int height) {    }    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mIsDrawing = false;    }    @Override    public void run() {        while (mIsDrawing) {            draw();            x += 1;            y = (int) (100*Math.sin(x * 2 * Math.PI / 180) + 400);            mPath.lineTo(x, y);        }    }    private void draw() {        try {            mCanvas = mHolder.lockCanvas();            // SurfaceView背景            mCanvas.drawColor(Color.WHITE);            mCanvas.drawPath(mPath, mPaint);        } catch (Exception e) {        } finally {            if (mCanvas != null)                mHolder.unlockCanvasAndPost(mCanvas);        }    }}

参考：Android群英传

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