eoe上既然看見了，就備份一下，少許更改了部分代碼：

    
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Bitmap.CompressFormat;
import android.os.Environment;
import android.view.MotionEvent;
import android.view.View;

/**
 * View實現涂鴉、撤銷以及重做功能
 */

public class TuyaView extends View {

	private Bitmap mBitmap;
	private Canvas mCanvas;
	private Path mPath;
	private Paint mBitmapPaint;// 畫布的畫筆
	private Paint mPaint;// 真實的畫筆
	private float mX, mY;// 臨時點坐標
	private static final float TOUCH_TOLERANCE = 4;
	
	// 保存Path路徑的集合,用List集合來模擬棧
	private static List<DrawPath> savePath;
	// 記錄Path路徑的對象
	private DrawPath dp;

	private int screenWidth, screenHeight;

	private class DrawPath {
		public Path path;// 路徑
		public Paint paint;// 畫筆
	}

	public TuyaView(Context context, int w, int h) {
		super(context);
		screenWidth = w;
		screenHeight = h;

		mBitmap = Bitmap.createBitmap(screenWidth, screenHeight, Bitmap.Config.ARGB_8888);
		// 保存一次一次繪制出來的圖形
		mCanvas = new Canvas(mBitmap);

		mBitmapPaint = new Paint(Paint.DITHER_FLAG);
		mPaint = new Paint();
		mPaint.setAntiAlias(true);
		mPaint.setStyle(Paint.Style.STROKE);
		mPaint.setStrokeJoin(Paint.Join.ROUND);// 設置外邊緣
		mPaint.setStrokeCap(Paint.Cap.ROUND);// 形狀
		mPaint.setStrokeWidth(5);// 畫筆寬度

		savePath = new ArrayList<DrawPath>();
	}

	@Override
	public void onDraw(Canvas canvas) {
		canvas.drawColor(0xFFAAAAAA);
		// 將前面已經畫過得顯示出來
		canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
		if (mPath != null) {
			// 實時的顯示
			canvas.drawPath(mPath, mPaint);
		}
	}

	private void touch_start(float x, float y) {
		mPath.moveTo(x, y);
		mX = x;
		mY = y;
	}

	private void touch_move(float x, float y) {
		float dx = Math.abs(x - mX);
		float dy = Math.abs(mY - y);
		if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
			// 從x1,y1到x2,y2畫一條貝塞爾曲線，更平滑(直接用mPath.lineTo也是可以的)
			mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
			mX = x;
			mY = y;
		}
	}

	private void touch_up() {
		mPath.lineTo(mX, mY);
		mCanvas.drawPath(mPath, mPaint);
		//將一條完整的路徑保存下來(相當于入棧操作)
		savePath.add(dp);
		mPath = null;// 重新置空
	}
	/**
	 * 撤銷的核心思想就是將畫布清空，
	 * 將保存下來的Path路徑最后一個移除掉，
	 * 重新將路徑畫在畫布上面。
	 */
	public void undo() {
		if (savePath != null && savePath.size() > 0) {
			savePath.remove(savePath.size() - 1);
			redrawOnBitmap();
		}
	}
	/**
	 * 重做
	 */
	public void redo(){
		if (savePath != null && savePath.size() > 0) {
			savePath.clear();
			redrawOnBitmap();
		}
	}
	
	private void redrawOnBitmap(){
		mBitmap = Bitmap.createBitmap(screenWidth, screenHeight,
				Bitmap.Config.ARGB_8888);
		mCanvas.setBitmap(mBitmap);// 重新設置畫布，相當于清空畫布 
		Iterator<DrawPath> iter = savePath.iterator();
		while (iter.hasNext()) {
			DrawPath drawPath = iter.next();
			mCanvas.drawPath(drawPath.path, drawPath.paint);
		}
		invalidate();// 刷新
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		float x = event.getX();
		float y = event.getY();

		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			// 每次down下去重新new一個Path
			mPath = new Path();
			//每一次記錄的路徑對象是不一樣的
			dp = new DrawPath();
			dp.path = mPath;
			dp.paint = mPaint;
			touch_start(x, y);
			invalidate();
			break;
		case MotionEvent.ACTION_MOVE:
			touch_move(x, y);
			invalidate();
			break;
		case MotionEvent.ACTION_UP:
			touch_up();
			invalidate();
			break;
		}
		return true;
	}

	public void saveToSDCard(){
		String fileUrl = Environment.getExternalStorageDirectory()
				.toString() + "/android/data/test.png";
		try {
			FileOutputStream fos = new FileOutputStream(new File(fileUrl));
			mBitmap.compress(CompressFormat.PNG, 100, fos);
			fos.flush();
			fos.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

  

    
import android.app.Activity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.KeyEvent;

public class TuyaActivity extends Activity {

	private TuyaView tuyaView = null;

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

		DisplayMetrics dm = new DisplayMetrics();
		getWindowManager().getDefaultDisplay().getMetrics(dm);

		tuyaView = new TuyaView(this, dm.widthPixels, dm.heightPixels);
		setContentView(tuyaView);
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {// 返回鍵
			tuyaView.undo();
			return true;
		}else if(keyCode == KeyEvent.KEYCODE_MENU){//MENU
			tuyaView.redo();
			return true;
		}
		return super.onKeyDown(keyCode, event);
	}

}

  

View實現涂鴉、撤銷以及重做功能