Android DrawingBoard demo

안드로이드에서 Double Buffering과 터치 이벤트로 그림 그리기

그려진 그림을 멀티터치 이벤트로 지우는 기능은 여기를 참조하세요

MainActivity.java

package com.example.androidapp;


import android.app.Activity;
import android.graphics.Point;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.TextView;

public class MainActivity extends Activity {
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new DrawingBoard(this));
	}
}

DrawingBoard.java

package com.example.androidapp;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Paint.Cap;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;

public class DrawingBoard extends View {
	
	Canvas cacheCanvas;
	Bitmap backBuffer;
	int width, height;
	Paint paint;
        int lastX, lastY, currX, currY;
	
	public DrawingBoard(Context context) {
		super(context);
		init();
	}

	public DrawingBoard(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
	}
	
	
	private void init() {
		setBackgroundColor(Color.WHITE);
		WindowManager wm = (WindowManager) 
				getContext().getSystemService(Context.WINDOW_SERVICE);
		width = wm.getDefaultDisplay().getWidth();
		height = wm.getDefaultDisplay().getHeight();

		cacheCanvas = new Canvas();
		backBuffer = Bitmap.createBitmap( width, height, Bitmap.Config.ARGB_8888);
		cacheCanvas.setBitmap(backBuffer);
		
		paint = new Paint();
		paint.setColor(Color.BLUE);
		paint.setStrokeWidth(10);
		paint.setStrokeCap(Paint.Cap.ROUND);
		paint.setStrokeJoin(Paint.Join.ROUND);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		super.onTouchEvent(event);
		int action = event.getAction();
		switch(action) {
		case MotionEvent.ACTION_DOWN:
			lastX = (int) event.getX();
			lastY = (int) event.getY();
			break;
		case MotionEvent.ACTION_MOVE:
			currX = (int) event.getX();
			currY = (int) event.getY();
			cacheCanvas.drawLine(lastX, lastY, currX, currY, paint);
			lastX = currX;
			lastY = currY;
			break;
		case MotionEvent.ACTION_UP:
			break;
		}
		invalidate();
		return true;
	}
	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		if(clientHeight==0) {
			clientHeight = getClientHeight();
			height = clientHeight;
			backBuffer = Bitmap.createBitmap( width, height, Bitmap.Config.ARGB_8888);
			cacheCanvas.setBitmap(backBuffer);
		}
		canvas.drawBitmap(backBuffer, 0, 0, null); //back buffer에 그려진 비트맵을 스크린 버퍼에 그린다
	}
	/* 상태바, 타이틀바를 제외한 클라이언트 영역의 높이를 구한다 */
	private int getClientHeight() {
	    Rect rect= new Rect();    
	    Window window = ((Activity)context).getWindow();     
	    window.getDecorView().getWindowVisibleDisplayFrame(rect);     
	    int statusBarHeight= rect.top;    
	    int contentViewTop= window.findViewById(Window.ID_ANDROID_CONTENT).getTop();     
	    int titleBarHeight= contentViewTop - statusBarHeight;
	    return ((Activity)context).getWindowManager().getDefaultDisplay().
	    		getHeight() - statusBarHeight - titleBarHeight;
	}
}