Android(安卓)Canvas

今天趁有空熟悉一下Canvas基本绘图方法：

public class MyView extends View{    private Bitmap bm;    private Paint paint;    private Rect srcRect;    private Rect dstRect;    public MyView(Context context) {        super(context);        // TODO Auto-generated constructor stub    }        public MyView(Context context,AttributeSet set)    {        super(context,set);         bm = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);         paint = new Paint();         srcRect = new Rect(0,0,50,50);         dstRect = new Rect(200,200,250,250);                               }    /* (non-Javadoc)     * @see android.view.View#onDraw(android.graphics.Canvas)     */    @SuppressLint("DrawAllocation")    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        paint.setAlpha(125);        paint.setColor(Color.BLACK);        paint.setAntiAlias(true);//低分辨率放到高分辨的屏幕的时候，图片会产生锯齿，设置抗锯齿可以柔化边缘                        canvas.drawColor(Color.WHITE);//绘制背景        canvas.drawBitmap(bm, 0, 0, paint);//左上角完全显示+透明度        canvas.drawBitmap(bm,50,50, paint);//左上角偏离左边框50px,上边框50px完全显示+透明度        canvas.drawBitmap(bm,100,100,null);//左上角偏离左边框100px,上边框100px完全显示+透明度        canvas.drawBitmap(bm,srcRect,dstRect,null);//从bmp中挖去50*50中放到屏幕Piont(200,200)处                /**         * DrawCircle         */        canvas.drawCircle(400,50,50,paint);        paint.setColor(Color.RED);        paint.setAntiAlias(false);        canvas.drawCircle(500,50 ,50, paint);                /**         * drawLine         */        paint.setColor(Color.BLACK);        paint.setAntiAlias(true);        canvas.drawLine(350, 150, 700, 150, paint);        paint.setColor(Color.RED);        paint.setAntiAlias(false);        canvas.drawLine(350, 200, 700, 200, paint);                /**         * drawRect         */        paint.setColor(Color.BLACK);        paint.setAntiAlias(true);        paint.setStyle(Style.STROKE);//填充风格->点填充        canvas.drawRect(new Rect(350, 250, 500, 300), paint);        paint.setStyle(Style.FILL);//填充风格->全部填充        canvas.drawRect(new Rect(500, 250, 650, 300), paint);                //RoundRect        //RectF->float型        /**         * 第一个10是在X轴的半径         * 第二个10是在Y轴的半径         */        canvas.drawRoundRect(new RectF(350, 300, 500, 350), 10, 10, paint);        //椭圆        canvas.drawOval(new RectF(350, 350, 500, 400) , paint);        /**         * drawText         */        paint.setTextSize(24);        canvas.drawText("HELLO", 0,300, paint);                /**         * drawTextOnPath         */        Path path = new Path();        path.moveTo(26,360);        path.lineTo(54, 360);        path.lineTo(70, 392);        path.lineTo(40, 420);        path.lineTo(10, 392);        path.close();        canvas.drawPath(path,paint);                /**         * 第一个0是修改起始字符距离Path第一个点的距离         * 第二个0是->负数的话，远离Path;正数的话会看到字符串嵌在Path中         * 因为Android坐标系以左上角为起点，-10就是往上移动         */        canvas.drawTextOnPath("abcdefgh", path, 0,-10, paint);            }}

实际效果如下：

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