android自定义view

代码：

package com.example.brush;

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 Line extends View{

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

    public Line(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
    }
    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);
        Paint paint=new Paint();
        paint.setColor(Color.RED);
        paint.setTextSize(20);
        paint.setStrokeWidth(20);//设置现款
         canvas.drawLine(20, 20, 200, 200, paint);//直线 1.开始X 2.开始Y 3.结束X 4.结束Y 5.画笔
            canvas.drawText("我是被画出来的", 10, 100, paint);//文字 1.显示文字 2.开始X 3.开始Y 4.画笔
            canvas.drawCircle(55, 55, 50, paint);//圆 1.圆心X 2.圆心Y 3.半径 4.画笔
    }
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO Auto-generated method stub
//        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(200, 200);//画板宽高
    
    }
}

xml页面：

<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.example.brush.Line
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

MainActivity：

package com.example.day1_one;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

  
}

效果图：