Android canvas.drawArc() 画圆弧

public void drawArc(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter,
@NonNull Paint paint) {
drawArc(oval.left, oval.top, oval.right, oval.bottom, startAngle, sweepAngle, useCenter,
paint);
}

第一个参数：RectF oval

/**
* 这是一个居中的圆
*/
float x = (getWidth() - getHeight() / 2) / 2;
float y = getHeight() / 4;

RectF oval = new RectF( x, y,
getWidth() - x, getHeight() - y);

第二个参数：float startAngle

canvas.drawArc(oval,-90,120,false,mPaint);

canvas.drawArc(oval,90,110,false,mPaint);

//设置为-180的时候也是这样
canvas.drawArc(oval,180,140,false,mPaint);

//设置为360的时候也是这样
canvas.drawArc(oval,0,140,false,mPaint);

第三个参数：float sweepAngle

我们从上面的代码就可以知道其中的作用了

第四个参数：boolean useCenter

/**
*这里我是偷懒了，建议不要在onDraw()方法里初始化对象
*/
Paint p = new Paint();//这个是画矩形的画笔，方便大家理解这个圆弧
p.setStyle(Paint.Style.STROKE);
p.setColor(Color.RED);

mPaint.setAntiAlias(true);//取消锯齿
mPaint.setStyle(Paint.Style.FILL);//设置画圆弧的画笔的属性为描边(空心)，个人喜欢叫它描边，叫空心有点会引起歧义
mPaint.setStrokeWidth(mCircleWidth);
mPaint.setColor(Color.CYAN);

/**
* 这是一个居中的圆
*/
float x = (getWidth() - getHeight() / 2) / 2;
float y = getHeight() / 4;

RectF oval = new RectF( x, y,
getWidth() - x, getHeight() - y);

canvas.drawArc(oval,360,140,false,mPaint);//画圆弧，这个时候，绘制没有经过圆心
canvas.drawRect(oval, p);//画矩形

//当我们设置为true的时候，绘制的时候就经过圆心了
canvas.drawArc(oval,360,140,true,mPaint);

第五个参数：Paint paint

mPaint.setAntiAlias(true);//取消锯齿
mPaint.setStyle(Paint.Style.FILL);//设置画圆弧的画笔的属性为描边(空心)，个人喜欢叫它描边，叫空心有点会引起歧义
mPaint.setStrokeWidth(mCircleWidth);
mPaint.setColor(Color.CYAN);

public class CustomProgress extends View{

private Paint mPaint;

/**
* 圆的宽度
*/
private int mCircleWidth = 3;

public CustomProgress(Context context) {
this(context, null);
}

public CustomProgress(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public CustomProgress(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mPaint = new Paint();
}

@Override
protected void onDraw(Canvas canvas) {
mPaint.setAntiAlias(true);//取消锯齿
mPaint.setStyle(Paint.Style.FILL);
mPaint.setStrokeWidth(mCircleWidth);
mPaint.setColor(Color.CYAN);

/**
* 这是一个居中的圆
*/
float x = (getWidth() - getHeight() / 2) / 2;
float y = getHeight() / 4;

RectF oval = new RectF( x, y,
getWidth() - x, getHeight() - y);

canvas.drawArc(oval,360,140,true,mPaint);
}
}

那么，有关于如何画圆弧的笔记就到这里了，莎哟娜啦