Android繪製文字時垂直置中

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canvas.drawText(String text, float x, float y, Paint paint);

是Android中繪製文本的方法，其中的x代表文字繪製時在X軸的起始點，而y是在Y軸繪製時，文字的 baseline，不是文字的中心點也不是文字的底部。

下面代碼根據繪製的Y軸中心點centerY，算出了baseline，top，bottom，ascent和descent

    @Override    protected void onDraw(Canvas canvas) {        int top = mPaint.getFontMetricsInt().top;        int bottom = mPaint.getFontMetricsInt().bottom;        int ascent = mPaint.getFontMetricsInt().ascent;        int descent = mPaint.getFontMetricsInt().descent;        int baselineY =centerY + (bottom-top)/2 - bottom;        top = baselineY + top;        bottom = baselineY + bottom;        ascent = baselineY + ascent;        descent = baselineY + descent;        mPaint.setColor(Color.GREEN);        canvas.drawText(text, 100, baselineY, mPaint);        canvas.drawLine(0, centerY, getMeasuredWidth(), centerY, mPaint);        mPaint.setStrokeWidth(2);        mPaint.setColor(Color.BLACK);        canvas.drawLine(0, top, getMeasuredWidth(), top, mPaint);        mPaint.setColor(Color.YELLOW);        canvas.drawLine(0, ascent, getMeasuredWidth(), ascent, mPaint);        mPaint.setColor(Color.RED);        canvas.drawLine(0, baselineY, getMeasuredWidth(), baselineY, mPaint);        mPaint.setColor(Color.YELLOW);        canvas.drawLine(0, descent, getMeasuredWidth(), descent, mPaint);        mPaint.setColor(Color.BLACK);        canvas.drawLine(0, bottom, getMeasuredWidth(), bottom, mPaint);    }

 

Android繪製文字時垂直置中