Android之绘图

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一直对画画相关不感冒，但是Android的绘图机制还是要硬着头皮学

绘画主要是使用paint(画笔)在canvas(画布)进行各种图形的绘制，画矩形、圆、三角形等点线构成的2维图形

//矩形  drawRect (float left, float top, float right, float bottom, Paint paint)        canvas.drawRect(50, 100, 200, 200, paint);        //圆  drawCircle (float cx, float cy, float radius, Paint paint)        canvas.drawCircle(width / 2, height / 2, 100, paint);        //三角形（画线）        //实例化路径        Path path = new Path();        path.moveTo(80, 300);// 此点为多边形的起点        path.lineTo(120, 250);        path.lineTo(80, 250);        path.close(); // 使这些点构成封闭的多边形        canvas.drawPath(path, paint);        //扇形 RectF (float left, float top, float right, float bottom)        RectF rectF = new RectF(160, 200, 400, 400);        // drawArc (RectF oval, float startAngle 起始弧度, float sweepAngle 扫过的弧度, boolean useCenter, Paint paint)        canvas.drawArc(rectF, 200, 130, true, paint);        //椭圆        rectF = new RectF(300, 300, 600, 600);        //  set (float left, float top, float right, float bottom)        rectF.set(210,100,450,200);        // drawOval (RectF oval, Paint paint)        canvas.drawOval(rectF, paint);        //曲线        //设置空心        paint.setStyle(Paint.Style.STROKE);        path = new Path();        path.moveTo(500, 500);//设置Path的起点        path.quadTo(550, 510, 670, 600);  //设置路径点和终点        canvas.drawPath(path, paint);        //文字+ 图片        paint.setTextSize(30);        //文本 drawText (String text, float x, float y, Paint paint)        canvas.drawText("slack", 350, 330, paint);        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);        //图片 drawBitmap (Bitmap bitmap, float left, float top, Paint paint)        canvas.drawBitmap(bitmap, 320, 360, paint);

canvas有几个重要的方法，画图时会使用到，类似ps里的图层，旋转，位移的概念

/*     *  Canvas.save() 将之前的图像保存起来，让后续的操作能像在新的画布一样操作    *  Canvas.restore() 合并图层    *  Canvas.translate() 平移 我们绘制的时候默认坐标点事左上角的起始点，那么我们调用translate（x,y）之后，    则将原点（0,0）移动到（x,y）之后的所有绘图都是在这一点上执行的    *  Canvas.roate() 旋转    * */

画一个时钟，就把这些理解了

//画时钟        // 画外圆        Paint paintCircle = new Paint();        paintCircle.setAntiAlias(true);        paintCircle.setStyle(Paint.Style.STROKE);        paintCircle.setStrokeWidth(5);        canvas.drawCircle(width / 2, height / 2, width / 3, paintCircle);        // 画刻度        Paint paintDegree = new Paint();        paintDegree.setStrokeWidth(3);        canvas.rotate(30, width / 2, height / 2);        for (int i = 1; i <= 12; i++) {            // 区别整点和非整点            if (i == 3 || i == 6 || i == 9 || i == 12 ) {                paintDegree.setStrokeWidth(5);                paintDegree.setTextSize(30);                // drawLine (float startX, float startY, float stopX, float stopY, Paint paint)                canvas.drawLine(width / 2, height / 2 - width / 3,                        width / 2, height / 2 - width / 3 + 60, paintDegree);                String degree = String.valueOf(i);                canvas.drawText(degree,                        width / 2 - paintDegree.measureText(degree) / 3,                        height / 2 - width / 3 + 90, paintDegree);            } else {                paintDegree.setStrokeWidth(3);                paintDegree.setTextSize(15);                // 圆上的一点（x = 屏幕宽一半, y = 屏幕的一半 - 半径）                canvas.drawLine(width / 2, height / 2 - width / 3,                        width / 2, height / 2 - width / 3 + 30, paintDegree);                String degree = String.valueOf(i);                canvas.drawText(degree,                        width / 2 - paintDegree.measureText(degree) / 3,                        height / 2 - width / 3 + 60, paintDegree);            }            // 通过旋转画布——实际上是旋转了画图的坐标轴 简化坐标运算            canvas.rotate(30, width / 2, height / 2);        }        canvas.save();        // 画指针        Paint paintHour = new Paint();        paintHour.setStrokeWidth(15);        Paint paintMinute = new Paint();        paintMinute.setStrokeWidth(10);        //绘制的时候默认坐标点事左上角的起始点，那么我们调用translate（x,y）之后，则将原点（0,0）移动到（x,y）之后的所有绘图都是在这一点上执行的        canvas.translate(width / 2, height / 2);        canvas.drawPoint(0, 0, paintHour);//圆点        canvas.drawLine(0, 0, 100, 100, paintHour);        canvas.drawLine(0, 0, 100, -200, paintMinute);        canvas.restore();

模拟刮刮乐

// PorterDuffXfermode 刮刮乐 通过DST_IN.SRC_IN模式来实现将一个矩形变成圆角图片的效果        mPaint = new Paint();        mPaint.setAlpha(0);        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));        mPaint.setStyle(Paint.Style.STROKE);        mPaint.setStrokeJoin(Paint.Join.ROUND);        mPaint.setStrokeWidth(50);        mPaint.setStrokeCap(Paint.Cap.ROUND);        mPath = new Path();        // createBitmap (int width, int height, Bitmap.Config config)        mFgBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);        mCanvas = new Canvas(mFgBitmap);        mCanvas.drawColor(Color.GRAY);

/**     * 触摸事件     * 画一条透明的线  曲线     * @param event     * @return     */    @Override    public boolean onTouchEvent(MotionEvent event) {        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:                mPath.reset();                lastX = event.getX();                lastY = event.getY();                mPath.moveTo(lastX, lastY);//起点                break;            case MotionEvent.ACTION_UP:                mPath.lineTo(event.getX(), event.getY());                break;            case MotionEvent.ACTION_MOVE:                //移动时，记录这一次的点位置                mPath.quadTo(lastX, lastY, event.getX(), event.getY());  //设置曲线路径点和终点                lastX = event.getX();                lastY = event.getY();                break;        }        mCanvas.drawPath(mPath, mPaint);        invalidate();        return true;    }

@Override    public void draw(Canvas canvas) {        super.draw(canvas);        //刮刮乐        canvas.drawBitmap(mFgBitmap, 0, 0, null);    }

SurfaceView主要用于频繁刷新处，做一个画板

SurfaceView的简单使用也简单

public class SurfaView extends SurfaceView implements SurfaceHolder.Callback, Runnable

在线程里处理绘画的事件，贴上代码

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.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceView;/** * SurfaceView的使用 * Created by chenling on 2016/5/9. * 1.View主要用于自动更新的情况下,而surfaceVicw主要适用于被动更新,例如频繁刷新 * 2.View在主线程中刷新，而surfaceView通常会通过一 个子线程来进行页面刷新。 * 3.View在绘制的时候没有双缓冲机制,而surfaceVicw在底层实现机制中就已经实现了双缓冲机制； */public class SurfaView extends SurfaceView implements SurfaceHolder.Callback, Runnable {    //SurfaceHolder    private SurfaceHolder mHolder;    //用于绘制的Canvas    private Canvas mCanvas;    //子线程标志位    private boolean mIsDrawing;    private float lastX,lastY;    private Path mPath;    private Paint mPaint;    /**     * 构造方法     *     * @param context     * @param attrs     */    public SurfaView(Context context, AttributeSet attrs) {        super(context, attrs);        mPath = new Path();        mPaint = new Paint();        mPaint.setStrokeWidth(20);        mPaint.setAntiAlias(true);        mPaint.setStyle(Paint.Style.STROKE);        mHolder = getHolder();        mHolder.addCallback(this);        setFocusable(true);        setFocusableInTouchMode(true);        setKeepScreenOn(true);    }    // 创建    @Override    public void surfaceCreated(SurfaceHolder holder) {        mIsDrawing = true;        new Thread(this).start();    }    // 改变    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {    }    //销毁    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mIsDrawing = false;    }    @Override    public void run() {        while (mIsDrawing) {            draw();//            lastX += 1;//            lastY = (int) (100 * Math.sin(lastX * 2 * Math.PI / 180) + 400);//            mPath.lineTo(lastX, lastY);        }    }    // 负责绘画，频繁刷新    private void draw() {        try {            mCanvas = mHolder.lockCanvas();            mCanvas.drawColor(Color.WHITE);            mCanvas.drawPath(mPath, mPaint);        } catch (Exception e) {        } finally {            if (mCanvas != null) {                //提交                mHolder.unlockCanvasAndPost(mCanvas);            }        }    }    /**     * 触摸事件     *     * @param event     * @return     */    @Override    public boolean onTouchEvent(MotionEvent event) {        lastX =  event.getX();        lastY =  event.getY();        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:                mPath.moveTo(lastX, lastY);                break;            case MotionEvent.ACTION_MOVE:                mPath.lineTo(lastX,lastY);                break;            case MotionEvent.ACTION_UP:                break;        }        return true;    }}

附件：源码：https://github.com/CL-window/android_paint

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