package com.loaderman.customviewdemo;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Rect;

import android.util.AttributeSet;

import android.view.View;

public class MinTextRectView extends View {

    public MinTextRectView(Context context, AttributeSet attrs) {

        super(context, attrs);

    }

    @Override

    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);

        String text = "harvic\'s blog";

        int baseLineY = 90;

        int baseLineX = 0 ;

        //设置paint

        Paint paint = new Paint();

        paint.setTextSize(60); //以px为单位

        paint.setTextAlign(Paint.Align.LEFT);

        //画text所占的区域

        Paint.FontMetricsInt fm = paint.getFontMetricsInt();

        int top = baseLineY + fm.top;

        int bottom = baseLineY + fm.bottom;

        int width = (int)paint.measureText(text);

        Rect rect = new Rect(baseLineX,top,baseLineX+width,bottom);

        paint.setColor(0xA0888888);

        canvas.drawRect(rect,paint);

        //画最小矩形

        Rect minRect = new Rect();

        paint.getTextBounds(text,0,text.length(),minRect);

        minRect.top = baseLineY + minRect.top;

        minRect.bottom = baseLineY + minRect.bottom;

        paint.setColor(Color.BLACK);

        canvas.drawRect(minRect,paint);

        //写文字

        paint.setColor(Color.WHITE);

        canvas.drawText(text, baseLineX, baseLineY, paint);

    }

}

package com.loaderman.customviewdemo;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.util.AttributeSet;

import android.view.View;

public class MyTextView extends View {

    public MyTextView(Context context, AttributeSet attrs) {

        super(context, attrs);

    }

    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);

        canvas.drawColor(Color.WHITE);

        int baseLineY = 90;

        int baseLineX = 0;

        Paint paint = new Paint();

        //写文字

        paint.setColor(Color.BLACK);

        paint.setTextSize(60); //以px为单位

        paint.setTextAlign(Paint.Align.LEFT);

        canvas.drawText("harvic\'s blog", baseLineX, baseLineY, paint);

        //计算各线在位置

        Paint.FontMetrics fm = paint.getFontMetrics();

        float ascent = baseLineY + fm.ascent;

        float descent = baseLineY + fm.descent;

        float top = baseLineY + fm.top;

        float bottom = baseLineY + fm.bottom;

        //画基线

        paint.setColor(Color.RED);

        canvas.drawLine(baseLineX, baseLineY, 3000, baseLineY, paint);

        //画top

        paint.setColor(Color.BLUE);

        canvas.drawLine(baseLineX, top, 3000, top, paint);

        //画ascent

        paint.setColor(Color.GREEN);

        canvas.drawLine(baseLineX, ascent, 3000, ascent, paint);

        //画descent

        paint.setColor(Color.GREEN);

        canvas.drawLine(baseLineX, descent, 3000, descent, paint);

        //画bottom

        paint.setColor(Color.RED);

        canvas.drawLine(baseLineX, bottom, 3000, bottom, paint);

    }

}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

    <com.loaderman.customviewdemo.MinTextRectView

        android:layout_width="match_parent"

        android:layout_height="300dp"/>

    <com.loaderman.customviewdemo.MyTextView

        android:layout_width="match_parent"

        android:layout_height="300dp"/>

</LinearLayout>