Android 如何绘制text 为居中显示

mTextPaint = new TextPaint();
mTextPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
mTextPaint.setTextAlign(Paint.Align.LEFT);

mTextPaint.setTextSize(mExampleDimension);
mTextPaint.setColor(mExampleColor);
mTextWidth = mTextPaint.measureText(mExampleString);

Paint.FontMetrics fontMetrics = mTextPaint.getFontMetrics();
mTextHeight = fontMetrics.bottom -fontMetrics.top;
mTop = fontMetrics.top;

int paddingLeft = getPaddingLeft();
int paddingTop = getPaddingTop();
int paddingRight = getPaddingRight();
int paddingBottom = getPaddingBottom();

int contentWidth = getWidth() - paddingLeft - paddingRight;
int contentHeight = getHeight() - paddingTop - paddingBottom;

// Draw the text.
canvas.drawText(mExampleString,
paddingLeft + (contentWidth - mTextWidth) / 2,
paddingTop + (contentHeight - mTextHeight) / 2 - mTop,
mTextPaint);