学步园

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.javaeye.com/topic/474526)

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); 

        }

    }

}