与SurfaceView的初次见面

SurfaceView适用于被动更新，通过子线程来进行页面的刷新,使用双缓冲机制。
一般实现SurfaceHolder.Callback 和 Runnable接口。
当SurfaceHolder被销毁的时候回调
surfaceCreated（SurfaceHolder holder）
开始绘制

当SurfaceHolder的尺寸发生变化的时候被回调。
surfaceChange(SurfaceHolder holder, int format, int width, int height)

当SurfaceHolder被创建的时候回调
surfaceDestroyed(SurfaceHolder holder)
一般用于释放资源，或者结束绘图

下面画了一个用SurfaceView画了一个正弦波。

package com.example.administrator.youku_animi;

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


/**
 * Created by Administrator on 2017/8/3 0003.
 */

public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback, Runnable
{

    private SurfaceHolder mHolder;
    private Canvas mCanvas;
    private boolean mIsDrawing;
    private Paint mPaint;
    private Path path;
    int x = 0, y;


    public MySurfaceView(Context context){
        super(context);
        initView();
    }
    public MySurfaceView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        initView();
    }

    /*
    *@author
    *
    *
    *初始化函数
    *create at 2017/8/3 0003 下午 23:11
    */
    private  void initView()
    {
        mHolder = getHolder();
        mHolder.addCallback(this);
        setFocusable(true);
        setFocusableInTouchMode(true);
        this.setKeepScreenOn(true);
        path = new Path();
        path.setLastPoint(0, 400);

        mPaint = new Paint();
        mPaint.setColor(Color.BLACK);
        mPaint.setStrokeWidth(2);
        mPaint.setStyle(Paint.Style.STROKE);
    }

    /*
    *@author
    *
    *
    *
    *create at 2017/8/3 0003 下午 23:10
    */
    @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;
    }

    /*
    *@author
    *
    *
    *画正选波
    *create at 2017/8/3 0003 下午 23:09
    */
    @Override
    public void run()
    {
        while (mIsDrawing)
        {
            draw();
            x += 1;
            y = (int) (100 * Math.sin(x * 2 * Math.PI / 180) + 400);
            path.lineTo(x, y);
        }

    }

    private void draw()
    {
        try
        {
            //锁定画布
            mCanvas = mHolder.lockCanvas();
            //draw something
            //给画布设置颜色为白色
            mCanvas.drawColor(Color.WHITE);
            //画路径
            mCanvas.drawPath(path, mPaint);
        }
        catch (Exception e)
        {

        }
        finally {
            if (mCanvas != null)
            {
                //解锁画布
                mHolder.unlockCanvasAndPost(mCanvas);
            }
        }
    }
}