android中canvas.drawText参数的介绍以及绘制一个文本居中的案例

float baseline = height/2 + mPaint.getTextSize()/2 - mPaint.getFontMetrics().descent;文字尺寸就是

protected void onDraw(Canvas canvas) {
    String testString = "测试：gafaeh:1234";
    Paint mPaint = new Paint();
    mPaint.setStrokeWidth(3);
    mPaint.setTextSize(40);
    mPaint.setColor(Color.RED);
    mPaint.setTextAlign(Align.LEFT);
    Rect bounds = new Rect();
    mPaint.getTextBounds(testString, 0, testString.length(), bounds);
    FontMetricsInt fontMetrics = mPaint.getFontMetricsInt();
    int baseline = (getMeasuredHeight() + mPaint.getTextSize) / 2 - fontMetrics.descent;
    canvas.drawText(testString,getMeasuredWidth() / 2 - bounds.width() / 2, baseline, mPaint);
}