RadioButton小红点、数字角标的实现

 

RadioButton通常作为RadioGroup的子布局嵌套在里面，单独使用不太常用，本文实现RadioButton小红点、数字角标，主要是利用onDraw方法进行重写，绘制小红点、数字角标。如下：

   

public class AppRadioButton extends AppCompatRadioButton {

    private Paint mPaint;
    private boolean isShowDot;
    private boolean isShowNumberDot;

    //小红点半径
    private final int circleDotRadius = UIUtils.dp2px(4);
    //icon的尺寸，高 == 宽
    private final int drawableSize = UIUtils.dp2px(22);
    //小红点距离icon的padding
    private final int drawablePadding = UIUtils.dp2px(2);
    //矩形角标数字左右padding
    private final int rectFPaddingX = UIUtils.dp2px(4);
    //矩形角标数字上下padding
    private final int rectFPaddingY = UIUtils.dp2px(3);
    //角标矩形背景
    private int rectFRadius = UIUtils.dp2px(8);
    //圆点和角标颜色
    private final int PAINT_COLOR_DEFAULT = Color.parseColor("#FD481E");

    private String numberText;

    /**
     * 圆点和未读消息的坐标
     */
    private float pivotX;
    private float pivotY;

    public AppRadioButton(Context context) {
        super(context);
        init();
    }

    public AppRadioButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public AppRadioButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mPaint = new Paint();
        mPaint.setStrokeWidth(2);
        mPaint.setAntiAlias(true);
        mPaint.setColor(PAINT_COLOR_DEFAULT);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.translate(getScrollX(), 0);
        pivotX = getWidth() / 2 + drawableSize / 2 + drawablePadding;
        pivotY = getHeight() / 2 - drawableSize / 2 - drawablePadding;
        if (isShowDot) {
            canvas.drawCircle(pivotX, pivotY, circleDotRadius, mPaint);
        } else if (isShowNumberDot && !TextUtils.isEmpty(numberText)) {
            if (Integer.parseInt(numberText) > 99) {
                numberText = "99+";
            }
            if (numberText.length() == 1) {
                rectFRadius = UIUtils.dp2px(6);
            }
            mPaint.setColor(PAINT_COLOR_DEFAULT);
            mPaint.setTextSize(UIUtils.dp2px(12));
            float textWidth = mPaint.measureText(numberText);
            Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
            float textHeight = Math.abs((fontMetrics.top + fontMetrics.bottom));
            RectF rect = new RectF(pivotX - UIUtils.dp2px(4), pivotY - textHeight / 2 - rectFPaddingY, pivotX + textWidth + rectFPaddingX * 2, pivotY + textHeight / 2 + rectFPaddingY);
            canvas.drawRoundRect(rect, rectFRadius, rectFRadius, mPaint);
            mPaint.setColor(Color.parseColor("#ffffff"));
            float baseline = (rect.bottom + rect.top - fontMetrics.bottom - fontMetrics.top) / 2 - UIUtils.dp2px(1);
            mPaint.setTextAlign(Paint.Align.CENTER);
            //绘制文本
            canvas.drawText(numberText, pivotX + textWidth / 2 + rectFPaddingX - UIUtils.dp2px(4) / 2, baseline, mPaint);
        }
    }

    /**
     * `
     * 设置是否显示小圆点
     */
    public void setShowSmallDot(boolean isShowDot) {
        this.isShowDot = isShowDot;
        invalidate();
    }

    /**
     * 设置是否显示数字
     */
    public void setNumberDot(boolean isShowNumberDot, @NonNull String text) {
        this.isShowNumberDot = isShowNumberDot;
        this.numberText = text;
        if (isShowNumberDot) {
            isShowDot = false;
        }
        invalidate();
    }
}

实现原理如上标注，效果很不错，如果有特殊需求，上下左右显示不同的样式显示也可以在onDraw上面修改。