绘制文字时如何让文字居中显示

理解：x：要绘制文本的x坐标，y:baseline

1.首先调整字符的坐标系为中心，

paintUnselectWeekText.setTextAlign(Paint.Align.CENTER);

2.将字符的中心与要绘制的地方的中心对其，那么文字就居中了

canvas.drawText("the text", widthToPlace /2, getPaddingTop() + textHeight, paint) 

    FontMetricsInt fontMetrics = paint.getFontMetricsInt();
    int baseline = targetRect.top + (targetRect.bottom - targetRect.top - fontMetrics.bottom + fontMetrics.top) / 2 - fontMetrics.top;
    paint.setTextAlign(Paint.Align.CENTER);
    canvas.drawText(testString, targetRect.centerX(), baseline, paint);