View实现涂鸦、撤销以及重做功能

Java代码
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实现涂鸦、撤销以及重做功能
*/

public class TuyaView extends View {

    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Path mPath;
    private Paint mBitmapPaint;// 画布的画笔
    private Paint mPaint;// 真实的画笔
    private float mX, mY;// 临时点坐标
    private static final float TOUCH_TOLERANCE = 4;

    // 保存Path路径的集合,用List集合来模拟栈
    private static List<DrawPath> savePath;
    // 记录Path路径的对象
    private DrawPath dp;

    private int screenWidth, screenHeight;

    private class DrawPath {
        public Path path;// 路径
        public Paint paint;// 画笔
    }

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

        mBitmap = Bitmap.createBitmap(screenWidth, screenHeight, Bitmap.Config.ARGB_8888);
        // 保存一次一次绘制出来的图形
        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);// 设置外边缘
        mPaint.setStrokeCap(Paint.Cap.ROUND);// 形状
        mPaint.setStrokeWidth(5);// 画笔宽度

        savePath = new ArrayList<DrawPath>();
    }

    @Override
    public void onDraw(Canvas canvas) {
        canvas.drawColor(0xFFAAAAAA);
        // 将前面已经画过得显示出来
        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
        if (mPath != null) {
            // 实时的显示
            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) {
            // 从x1,y1到x2,y2画一条贝塞尔曲线，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);
        //将一条完整的路径保存下来(相当于入栈操作)
        savePath.add(dp);
        mPath = null;// 重新置空
    }
    /**
     * 撤销的核心思想就是将画布清空，
     * 将保存下来的Path路径最后一个移除掉，
     * 重新将路径画在画布上面。
     */
    public void undo() {
        if (savePath != null && savePath.size() > 0) {
            savePath.remove(savePath.size() - 1);
            redrawOnBitmap();
        }
    }
    /**
     * 重做 www.zzzyk.com
     */
    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);// 重新设置画布，相当于清空画布
        Iterator<DrawPath> iter = savePath.iterator();
        while (iter.hasNext()) {
            DrawPath drawPath = iter.next();
  &nb

补充：移动开发 , Android ,