自定义view

package com.bwie.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.widget.TextView;

public class SelfView extends TextView {

    public SelfView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }

    public SelfView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

    public SelfView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        
        // 创建一个画笔
        Paint paint = new Paint();
        // 设置画笔的颜色为蓝绿色
        paint.setColor(Color.CYAN);
        // 设置画笔的字体大小
        paint.setTextSize(25);
        // 设置画笔的线条宽度
        paint.setStrokeWidth(20);
        
        // 画板为灰色
        canvas.drawColor(Color.GRAY);
        //画一条直线
        canvas.drawLine(20, 280, 280, 280, paint);//1.开始X 2.开始Y 3.结束X 4.结束Y. 5.画笔
        //画文字                                            
        canvas.drawText("我是被自定义出来的", 10, 250, paint);//1.显示文字 2.开始X 3.开始Y 4.画笔
        //画圆
        canvas.drawCircle(80, 80, 80, paint);//1.圆心X 2.圆心Y 3.半径 4.画笔
        super.onDraw(canvas);
        
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO Auto-generated method stub
        setMeasuredDimension(300, 300);//设置画板大小
    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

   <com.bwie.view.SelfView
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_centerInParent="true"
       />

</RelativeLayout>