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自定义控件的时候经常会遇到需要画弧线、话矩形。 这就要用到RectF方法。

先解释一下RectF的几个属性

• RectF.left 矩形左上角的x坐标。
• RectF.top 矩形左上角的y坐标。
• RectF.right 矩形右下角的y坐标。
• RectF.right 矩形右下角的y坐标。
  
  使用方法

public class MyView extends View {
       private String TAG = "MyView ";    private int mRadius;    private int mX;    private int mY;    private float mCenterX;    private float mCenterY;    private RectF mRectF;    public MyView (Context context, AttributeSet attrs) {
           super(context, attrs);        Log.i(TAG,"MyView ");    }    @Override    public void draw(Canvas canvas) {
           super.draw(canvas);        Log.i(TAG,"draw");                //RectF设置        mRectF = new RectF();        mRectF.left = mCenterX - mRadius;        mRectF.top =mCenterY - mRadius;        mRectF.right = mCenterX + mRadius;        mRectF.bottom = mCenterY + mRadius;        //矩形画笔        Paint mRectPaint = new Paint();        mRectPaint.setColor(Color.BLUE);        mRectPaint.setStrokeWidth(20);        mRectPaint.setStyle(Paint.Style.STROKE);        //画矩形        canvas.drawRect(mRectF,mRectPaint);        //圆弧画笔        Paint mArcPaint = new Paint();        mArcPaint.setColor(Color.RED);        mArcPaint.setStrokeWidth(20);        mArcPaint.setStyle(Paint.Style.STROKE);        //画圆弧        //startAngle 圆弧开始位置，从3点钟方向开始        //sweepAngle 圆弧弧度        //useCenter ,false为空心圆弧，true为实心（扇形）圆弧        canvas.drawArc(mRectF,0,180,false,mArcPaint);    }    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
           super.onSizeChanged(w, h, oldw, oldh);        Log.i(TAG,"onSizeChanged ");        mX = w;        mY = h;        mRadius = w/4;        mCenterX = mX/2;        mCenterY = mY/2;    }}

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