Android(安卓)Canvas drawArc方法介绍

public void drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint)

本例演示了drawArc的四种不同用法,

1. 填充圆弧但不含圆心：

mPaints[0] =newPaint();

mPaints[0].setAntiAlias(true);

mPaints[0].setStyle(Paint.Style.FILL);

mPaints[0].setColor(0x88FF0000);

mUseCenters[0] =false;

2. 填充圆弧带圆心（扇形）

mPaints[1] =newPaint(mPaints[0]);

mPaints[1].setColor(0x8800FF00);

mUseCenters[1] =true;

3. 只绘圆周，不含圆心

mPaints[2] =newPaint(mPaints[0]);

mPaints[2].setStyle(Paint.Style.STROKE);

mPaints[2].setStrokeWidth(4);

mPaints[2].setColor(0x880000FF);

mUseCenters[2] =false;

4. 只绘圆周，带圆心（扇形）

mPaints[3] =newPaint(mPaints[2]);

mPaints[3].setColor(0x88888888);

mUseCenters[3] =true;

本例的onDraw

protectedvoidonDraw(Canvas canvas) {

canvas.drawColor(Color.WHITE);

drawArcs(canvas, mBigOval, mUseCenters[mBigIndex],

mPaints[mBigIndex]);

for(inti =0; i <4; i++) {

drawArcs(canvas, mOvals[i], mUseCenters[i], mPaints[i]);

}

mSweep += SWEEP_INC;

if(mSweep >360) {

mSweep -=360;

mStart += START_INC;

if(mStart >=360) {

mStart -=360;

}

mBigIndex = (mBigIndex +1) % mOvals.length;

}

invalidate();

}

同样onDraw之中调用invalidate()，会再触发onDraw，从而不停刷新显示，startAngle, sweepAngle周而复始，形成动画效果，最上的大图顺序显示drawArc的这四种用法：

Paint.Style.STROKE 表示当前只绘制图形的轮廓，而Paint.Style.FILL表示填充图形。

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