class MainActivity

package com.example.choi.ex07_graphic;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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


    public  void onClick(View v){
        Intent intent=null;

        switch(v.getId()){

            case R.id.button1:
                intent=new Intent(this, ShapeActivity.class);
                break;
        }

        startActivity(intent);
    }


}

 

 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.choi.ex07_graphic.MainActivity">

    <Button
        android:text="도형 그리기"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:id="@+id/button1"
        android:onClick="onClick" />
</RelativeLayout>

 

 

 

 

class ShapeActivity

package com.example.choi.ex07_graphic;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

public class ShapeActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //xml 이 아닌 코드를 사용한 뷰(커스텀뷰)
        setContentView(new MyView(this));
    }


    //내부 클래스
    class MyView extends View {
        //Alt + Insert , 생성자 추가

        public MyView(Context context) {
            super(context);
        }

        //화면출력
        @Override
        protected void onDraw(Canvas canvas) {
         //canvas :도화지 역할(바탕화면)
            canvas.drawColor(Color.LTGRAY);//바탕화면 색상
         //Paint :붓 역할
            Paint p=new Paint();
            p.setColor(Color.GREEN); //색상 설정
         //캔버스에 원 그리기 (x, y, width, paint)
            canvas.drawCircle(100, 100, 50, p);
          //사각형 그리기 (x1, y1, x2, y2, 페이트)
            canvas.drawRect(200, 200, 300, 300, p);

        }
    }



}