文字 单元格居中显示 paint ascent descent baseline 文字显示 尺寸 格式

基线（baeseline），坡顶（ascenter）,坡底（descenter）
上坡度（ascent），下坡度（descent）
行间距（leading）：坡底到下一行坡顶的距离
字体的高度＝上坡度＋下坡度＋行间距

ascent是指从一个字的基线(baseline)到最顶部的距离，descent是指一个字的基线到最底部的距离

注意, ascent和top都是负数

下面代码实现高度只有0.75单元格高度的居中显示，所以要下移一定距离y。

foreground.setStyle(Style.FILL);
foreground.setTextSize(height * 0.75f);
foreground.setTextScaleX(width / height);
foreground.setTextAlign(Paint.Align.CENTER);

// Draw the number in the center of the tile
FontMetrics fm = foreground.getFontMetrics();
// Centering in X: use alignment (and X at midpoint)
float x = width / 2;
// Centering in Y: measure ascent/descent first
float y = height / 2 - (fm.ascent + fm.descent) / 2;

网络的例子：（引用http://www.j<wbr>avaeye.com/t<wbr>opic/474526)</wbr></wbr>

package com.TextTest;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.FontMetrics;
import android.os.Bundle;
import android.view.View;

public class TextTest extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.main);
setContentView(new GraphView(this));
}

static public class GraphView extends View {
public GraphView(Context context) {
super(context);
}

@Override
protected void onDraw(Canvas canvas) {
//
Paint textPaint = new Paint( Paint.ANTI_ALIAS_FLAG);
textPaint.setTextSize(35);
textPaint.setColor(Color.WHITE);

// FontMetrics对象
FontMetrics fontMetrics = textPaint.getFontMetrics();
String text = "abcdefghijklmnopqrstu";

// 计算每一个坐标
float baseX = 0;
float baseY = 100;
float topY = baseY + fontMetrics.top;
float ascentY = baseY + fontMetrics.ascent;
float descentY = baseY + fontMetrics.descent;
float bottomY = baseY + fontMetrics.bottom;

// 绘制文本
canvas.drawText( text, baseX, baseY, textPaint);

// BaseLine描画
Paint baseLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
baseLinePaint.setColor(Color.RED);
canvas.drawLine(0, baseY, getWidth(), baseY, baseLinePaint);

// Base描画
canvas.drawCircle( baseX, baseY, 5, baseLinePaint);

// TopLine描画
Paint topLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
topLinePaint.setColor( Color.LTGRAY);
canvas.drawLine(0, topY, getWidth(), topY, topLinePaint);

// AscentLine描画
Paint ascentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
ascentLinePaint.setColor( Color.GREEN);
canvas.drawLine(0, ascentY, getWidth(), ascentY, ascentLinePaint);

// DescentLine描画
Paint descentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
descentLinePaint.setColor( Color.YELLOW);
canvas.drawLine(0, descentY, getWidth(), descentY, descentLinePaint);

// ButtomLine描画
Paint bottomLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
bottomLinePaint.setColor( Color.MAGENTA);
canvas.drawLine(0, bottomY, getWidth(), bottomY, bottomLinePaint);
}
}

}