paint之文字示例

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>

效果: