Font

文字最终的大小是和绘制文字的字体的类型和字体的大小是相关的.

设置字体类型 Paint.setTypeface(Typeface typeface)

设置字体大小 Paint.setTextSize(float textSize)

几个相关的尺寸和方法

Paint.FontMetrics

有5个属性,并且这5个属性都是跟字体相关的.

top: 字体中字符超出基线之上的最大距离
bottom: 字体中字符超出基线之下的最大距离
ascent: 单个字符超出基线之上的推荐距离
descent: 单个字符超出基线之上的推荐距离
leading: 标准行间距

Paint.getTextBounds

这个方法获取字符[字符串]占据的矩形区域,意为字体可见部分的矩形区域

Rect bound = new Rect();
mPaint.getTextBounds(text, 0, text.length(), bound);

bound.right - bound.left //得到的就是字符[字符串]的可见部分矩形区域的宽度

mPaint.measureText(text)

返回的是字符[字符串]的宽度,注意与

bound.right - bound.left

相互区分.

因为通常来说每个字符两边都会留有一部分空白区域,便于阅读.所以measureText的尺寸通常会大于bound.right - bound.left.所以,对于单个字符来说:

measureText = bound.right - bound.left + 字符两边的留白宽度

整体图示如下

应用场景

1. 垂直居中的文字,计算基线位置使用FontMetrics比较方便.

2. 或者大小不一的问题要实现对齐,使用getTextBounds比较方便.

3. 获取文字的理想宽度,使用measureText比较方便

图示代码

Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
Rect bound = new Rect();

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    mPaint.setTextSize(600);
    String text = "p";
    draw1(canvas, text, 800);
}

private void draw1(Canvas canvas, String text, float baseLineY) {

    mPaint.getTextBounds(text, 0, text.length(), bound);
    mPaint.setColor(Color.rgb(0xb4, 0xb4, 0xb4));
    canvas.drawRect(bound.left, bound.top + baseLineY, bound.right, bound.bottom + baseLineY, mPaint);

    float width = mPaint.measureText(text);
    mPaint.setColor(Color.rgb(0x00, 0x00, 0x00));
    canvas.drawRect(bound.left, bound.top + baseLineY - 30, bound.left + width, bound.top + baseLineY - 20, mPaint);

    Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
    mPaint.setColor(Color.BLACK);
    canvas.drawText(text, 0, baseLineY, mPaint);
    canvas.drawLine(0, baseLineY, getWidth(), baseLineY, mPaint);
    mPaint.setColor(Color.RED);
    canvas.drawLine(0, baseLineY + fontMetrics.top, getWidth(), baseLineY + fontMetrics.top, mPaint);
    canvas.drawLine(0, baseLineY + fontMetrics.bottom, getWidth(), baseLineY + fontMetrics.bottom, mPaint);
    mPaint.setColor(Color.BLUE);
    canvas.drawLine(0, baseLineY + fontMetrics.ascent, getWidth(), baseLineY + fontMetrics.ascent, mPaint);
    canvas.drawLine(0, baseLineY + fontMetrics.descent, getWidth(), baseLineY + fontMetrics.descent, mPaint);

}

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