Android---绘图机制---SurfaceView

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SurfaceView和View绘图的区别

View适用于主动更新的情况下,而SurfaceView适用于被动的更新,比如频繁的刷新.
View在主线程中对画面进行刷新,SurfaceView通过一个子线程对页面进行抓心
View在绘图时没有使用双缓冲机制,SurfaceView在底层机制中实现了双缓冲机制.

总结:如果自定义View需要频繁的刷新,或者刷新的数据量比较大的时候就要使用SurfaceView了

SurfaceView模板

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;    /**     * 三个构造方法     */    public SurfaceViewTemplate(Context context) {        super(context);        init();    }    public SurfaceViewTemplate(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    public SurfaceViewTemplate(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    //初始化    private void init() {        mHolder=getHolder();        mHolder.addCallback(this);        setFocusable(true);        setFocusableInTouchMode(true);        this.setKeepScreenOn(true);        //mHolder.setFormat(PixelFormat.OPAQUE);    }    //SurfaceView的创建    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing=true;        new Thread(this).start();    }    //SurfaceView的改变    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {    }    //SurfaceView的销毁    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mIsDrawing=false;    }    @Override    public void run() {        while (mIsDrawing){            draw();        }    }    private void draw() {        try {            //可以获得当前Canvas绘制的对象            mCanvas=mHolder.lockCanvas();            //绘制的东西在这里写入        }catch (Exception e){        }finally {            if (mCanvas!=null){                //提交                mHolder.unlockCanvasAndPost(mCanvas);            }        }    }}

屏幕绘制一个正弦函数

public class Sin 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;    private int x,y=0;    private Paint mPaint;    private Path mPath;    /**     * 三个构造方法     */    public Sin(Context context) {        super(context);        init();    }    public Sin(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    public Sin(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    //初始化    private void init() {        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);    }    //SurfaceView的创建    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing=true;        mPath.moveTo(0, 400);        new Thread(this).start();    }    //SurfaceView的改变    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {    }    //SurfaceView的销毁    @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 {            //可以获得当前Canvas绘制的对象            mCanvas=mHolder.lockCanvas();            //SurfaceView背景            mCanvas.drawColor(Color.YELLOW);            mCanvas.drawPath(mPath,mPaint);        }catch (Exception e){        }finally {            if (mCanvas!=null){                //提交                mHolder.unlockCanvasAndPost(mCanvas);            }        }    }}

这里写图片描述

在屏幕上绘制图形

public class Art 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;    private Path mPath;    private Paint mPaint;    /**     * 三个构造方法     */    public Art(Context context) {        super(context);        init();    }    public Art(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    public Art(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    //初始化    private void init() {        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);    }    //SurfaceView的创建    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing=true;        new Thread(this).start();    }    //SurfaceView的改变    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {    }    //SurfaceView的销毁    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mIsDrawing=false;    }    @Override    public void run() {        long start=System.currentTimeMillis();        while (mIsDrawing){            draw();        }        long end=System.currentTimeMillis();        //50-100之间        if (end-start<100){            try {                Thread.sleep(100-(end-start));            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }    private void draw() {        try {            //可以获得当前Canvas绘制的对象            mCanvas=mHolder.lockCanvas();            mCanvas.drawColor(Color.WHITE);            mCanvas.drawPath(mPath,mPaint);            //绘制的东西在这里写入        }catch (Exception e){        }finally {            if (mCanvas!=null){                //提交                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;            case MotionEvent.ACTION_UP:                break;        }        return true;    }}

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