더블 버퍼링

 

 

 

 

 

 

class MainActivity

package org.androidtown.mycustomview;

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.LinearLayout;

public class MainActivity extends AppCompatActivity {

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

        LinearLayout container =(LinearLayout)findViewById(R.id.container);


        MyView view =new MyView(this);
        view.setBackgroundColor(Color.CYAN);
        container.addView(view);

    }
}

 

 

R.layout.activity_main

 

<?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="org.androidtown.mycustomview.MainActivity">


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

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/button"
        android:id="@+id/container"></LinearLayout>
</RelativeLayout>

 

class MyView

package org.androidtown.mycustomview;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by choi on 2017-04-09.
 */

public class MyView extends View {

    Paint paint;
    Bitmap mBitmap;
    Canvas mCanvas;

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

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    private void init(Context context){
        paint =new Paint();
        paint.setAntiAlias(true);
    }


    //화면의 뷰가 결정되었을때 비트맵 메모리 객체를 만들 수 있다.


    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        if(w >0 && h>0){
            mBitmap =Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
            mCanvas =new Canvas();
            mCanvas.setBitmap(mBitmap);

            draw1();
        }

        super.onSizeChanged(w, h, oldw, oldh);
    }


    // 현재 화면에 그리는 것이 아니라
    // 메모리에 있는 비트맵 객체에 그린다.
    private void draw1(){

        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.RED);
        mCanvas.drawRect(100, 100, 200, 200, paint);


        paint.setStyle(Paint.Style.STROKE);
        //paint.setColor(Color.MAGENTA);
        paint.setARGB(128, 0, 255, 0); //반투명 그린
        paint.setStrokeWidth(10.0f); //굵기 지정
        mCanvas.drawRect(210, 210, 300, 300, paint);
/*

        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.BLUE);
        DashPathEffect effect =new DashPathEffect(new float[]{5,5},1);
        paint.setPathEffect(effect);
        mCanvas.drawLine(100, 400, 300, 600, paint);


        ShapeDrawable drawable1 =new ShapeDrawable();
        RectShape shape1 =new RectShape();
        shape1.resize(200, 200);
        drawable1.setShape(shape1);
        drawable1.setBounds(300, 100, 500, 300);
        drawable1.draw(mCanvas);


        LinearGradient gradient=new LinearGradient(400, 400, 400, 700, Color.RED, Color.YELLOW,
                Shader.TileMode.CLAMP);
        paint.setShader(gradient);
        shape1.resize(300, 300);
        drawable1.setBounds(400, 300, 700, 600);
        drawable1.draw(mCanvas);
*/

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //실제로 화면에 그린다.
        if(mBitmap!=null){
            canvas.drawBitmap(mBitmap, 0, 0, null);
        }

    }




}