SurfaceView与Timer实现动态绘图

来源：互联网发布：linux破解wifi工具包编辑：程序博客网时间：2024/05/16 02:15

在View的绘图时，必须在UI线程中更新画面，在对于比较费时的绘图中，有可能会降低UI的响应，造成不良的用户体验。因此在android中还提供了SurfaceView用于代替View绘图，SurfaceView是在新起的单独线程中完成重新绘图。

SurfaceView完成绘图需要SurfaceHolder的配合完成。

setFixedSize(WIDTH, HEIGHT);用于设置canvas的大小

SurfaceHolder提供 lockCanvas() 用于锁定SurfaceView对象，获取画布。

lockCanvas（Rect dirty）用于锁定SurfaceView对象的Rect区的Canvas，用于更新。

unlockCanvasAndPost（canvas）用于释放canvas，实现画布画面更新。

addCallbak 回调函数，包含三个方法;

public void surfaceCreated(SurfaceHolder myHolder) 用于创建时调用

public void surfaceChanged(SurfaceHolder holder, int format,int width, int height) ，在画布内容改变时调用。

public void surfaceDestroyed(SurfaceHolder holder)，销毁时调用。

TimerTask是基于Runable接口实现的线程

Timer中运行任务的方式有

schedule(task, time); //在指定时间执行一次任务

schedule(task, firstTime, period); //从firstTime开始，每隔period间隔，执行一次任务

schedule(task, delay); //从现在开始，过delay时间，执行任务一次

schedule(task, delay, period); //从现在开始，过delay时间，每隔period执行一次任务

绘制正弦，余弦函数实例

布局文件

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实例源码

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public class MainActivity extends Activity {

    private Button Sin;
    private Button Cos;
    private SurfaceView surface;
    private SurfaceHolder holder;
    private Paint paint;
    final int HEIGHT = 320;     //定义大小参数
    final int WIDTH = 768;
    final int X_OFFSET = 5;
    private int cx = X_OFFSET;
    int centerY = HEIGHT / 2;
    Timer timer = new Timer();

    private Sintask sintask;
    private Costask costask;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Sin = (Button) findViewById(R.id.Sin);
        Cos = (Button) findViewById(R.id.Cos);
        surface = (SurfaceView) findViewById(R.id.show);
        holder = surface.getHolder();
        holder.setFixedSize(WIDTH+10, HEIGHT+20);     //设置Canvas大小
        paint = new Paint();
        paint.setColor(Color.GREEN);
        paint.setStrokeWidth(3);
        Sin.setOnClickListener(new SinOnClick());
        Cos.setOnClickListener(new CosOnClick());
        holder.addCallback(new Callback() {
            @Override
            public void surfaceChanged(SurfaceHolder holder, int format,
                    int width, int height) {
                drawBack(holder);
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                timer.cancel();
            }

            @Override
            public void surfaceCreated(SurfaceHolder myHolder) {
                // TODO Auto-generated method stub
                //drawBack(holder);
            }
        });
    }

    private class SinOnClick implements OnClickListener {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            drawBack(holder);
            cx = X_OFFSET;
            if (sintask != null) {
                sintask.cancel();
            }
            if (costask != null) {
                costask.cancel();
            }
            sintask = new Sintask();          //创建正弦函数绘图任务
            new Thread(sintask).start();       //启动任务
            timer.schedule(sintask, 0, 30);    //每个30ms执行一次任务

        }

    }

    private class CosOnClick implements OnClickListener {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            drawBack(holder);
            cx = X_OFFSET;
            if (sintask != null) {
                sintask.cancel();
            }
            if (costask != null) {
                costask.cancel();
            }
            costask = new Costask();            //创建余弦函数绘图任务
            new Thread(costask).start();        //启动任务
            timer.schedule(costask, 0, 30);    //每个30ms执行一次任务

        }
    }

    private class Sintask extends TimerTask {
        public Sintask(){

        }
        @Override
        public void run() {
            // TODO Auto-generated method stub
            int cy = centerY
                    - (int) (100 * Math.sin((cx - 5) * 2 * Math.PI / 150));
            Canvas canvas = holder.lockCanvas(new Rect(cx, cy - 2, cx + 2,
                    cy + 2));
            canvas.drawPoint(cx,cy,paint);
            cx++;
            if (cx > WIDTH) {
                cancel();
            }
            holder.unlockCanvasAndPost(canvas);
        }
    }

    private class Costask extends TimerTask {
        @Override
        public void run() {
            // TODO Auto-generated method stub
            int cy = centerY
                    - (int) (100 * Math.cos((cx - 5) * 2 * Math.PI / 150));
            Canvas canvas = holder.lockCanvas(new Rect(cx, cy - 2, cx + 2,cy + 2));   //获取Rect区画布
            canvas.drawPoint(cx, cy, paint);              //画点
            cx++;
            if (cx > WIDTH) {
                cancel();
            }
            holder.unlockCanvasAndPost(canvas);     //释放Canvas
        }
    }

    private void drawBack(SurfaceHolder holder) {
        Canvas canvas = holder.lockCanvas();
        // 绘制黑背景
        canvas.drawColor(Color.BLACK);
        Paint p = new Paint();
        p.setColor(Color.WHITE);
        p.setStrokeWidth(2);
        // 绘制坐标轴
        canvas.drawLine(X_OFFSET, centerY, WIDTH, centerY, p);
        canvas.drawLine(X_OFFSET, 40, X_OFFSET, HEIGHT, p);
        holder.unlockCanvasAndPost(canvas);
        holder.lockCanvas(new Rect(0, 0, 0, 0));
        holder.unlockCanvasAndPost(canvas);
    }
}

程序运行效果

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