Android 从 0 开始学习自定义 View（二） 自定义圆弧

1.自定义 View 的基本流程

• 创建 View Class
• 创建 attr 属性文件，确定属性
• View Class 绑定 attr 属性
• onMeasure 测量
• onDraw 绘制

1.1 创建 View Class

public class ArcView extends View {
    public ArcView(Context context) {
        this(context, null);
    }
    public ArcView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }
    public ArcView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }
}

1.2 创建 attr 属性

1.3 绑定属性

private void initAttr(Context context, AttributeSet attrs) {
    TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.ArcView);
    //外环颜色
    mInnerColor = array.getColor(R.styleable.ArcView_arcInnerColor, mInnerColor);
    //内环颜色
    mOutColor = array.getColor(R.styleable.ArcView_arcOutColor, mOutColor);
    //环大小
    mWidth = (int) array.getDimension(R.styleable.ArcView_arcWidth, mWidth);
    //文字
    mText = array.getString(R.styleable.ArcView_arcText);
    //文字大小
    mTextSize = array.getDimensionPixelSize(R.styleable.ArcView_arcTextSize, mTextSize);
    //文字颜色
    mTextColor = array.getColor(R.styleable.ArcView_arcTextColor, mTextColor);
    array.recycle();
}

1.4 onMeasure

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    //确保正方形，将短边的大小设为狂傲
    //宽
    int width = MeasureSpec.getSize(widthMeasureSpec);
    //高
    int height = MeasureSpec.getSize(heightMeasureSpec);
    //设置宽高
    setMeasuredDimension(Math.min(width, height), Math.min(width, height));
}

1.5 onDraw

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
}

• 第一步，画内环

private void initInnerPaint() {
    mInnerPaint = new Paint();
    //抗锯齿
    mInnerPaint.setAntiAlias(true);
    //防抖动
    mInnerPaint.setDither(true);
    //宽度
    mInnerPaint.setStrokeWidth(mWidth);
    //颜色
    mInnerPaint.setColor(mInnerColor);
    //设置状态
    mInnerPaint.setStyle(Paint.Style.STROKE);
    //头部小圆点
    mInnerPaint.setStrokeCap(Paint.Cap.ROUND);
}

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //画内环
    RectF rectF = new RectF(mWidth / 2, mWidth / 2, getWidth() - mWidth / 2, getHeight() - mWidth / 2);
    canvas.drawArc(rectF, 135, 270, false, mInnerPaint);
}

内环

• 第二步，画外环

private void initOutPaint() {
    mOutPaint = new Paint();
    //抗锯齿
    mOutPaint.setAntiAlias(true);
    //防抖动
    mOutPaint.setDither(true);
    //宽度
    mOutPaint.setStrokeWidth(mWidth);
    //颜色
    mOutPaint.setColor(mOutColor);
    //设置状态
    mOutPaint.setStyle(Paint.Style.STROKE);
    //头部小圆点
    mOutPaint.setStrokeCap(Paint.Cap.ROUND);
}

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //画内环
    RectF rectF = new RectF(mWidth / 2, mWidth / 2, getWidth() - mWidth / 2, getHeight() - mWidth / 2);
    canvas.drawArc(rectF, 135, 270, false, mInnerPaint);
    //画内环
    if (MaxProgress == 0) return;
    float sweepAngle = (float) CurrentProgress / MaxProgress;
    canvas.drawArc(rectF, 135, sweepAngle * 270, false, mOutPaint);
}

外环

• 第三步，画文字

private void initTextPaint() {
    mTextPaint = new Paint();
    //抗锯齿
    mTextPaint.setAntiAlias(true);
    //文字大小
    mTextPaint.setTextSize(mTextSize);
    //文字颜色
    mTextPaint.setColor(mTextColor);
}

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //画内环
    RectF rectF = new RectF(mWidth / 2, mWidth / 2, getWidth() - mWidth / 2, getHeight() - mWidth / 2);
    canvas.drawArc(rectF, 135, 270, false, mInnerPaint);
    //画内环
    if (MaxProgress == 0) return;
    float sweepAngle = (float) CurrentProgress / MaxProgress;
    canvas.drawArc(rectF, 135, sweepAngle * 270, false, mOutPaint);
    //画文字
    //测量文字宽度
    Rect rect = new Rect();
    mTextPaint.getTextBounds(mText, 0, mText.length(), rect);
    int x = getWidth() / 2 - rect.width() / 2;
    //基线
    Paint.FontMetricsInt fontMetricsInt = mTextPaint.getFontMetricsInt();
    int y = (fontMetricsInt.bottom - fontMetricsInt.top) / 2 - fontMetricsInt.bottom;
    int baseline = getHeight() / 2 + y;
    canvas.drawText(mText, x, baseline, mTextPaint);
}

最终效果图

自定义圆弧就介绍到这里了，如果有什么写得不对的，可以在下方评论留言，我会第一时间改正。

Github 源码链接