Android画布撤销和重做操作

Question

我正在进行一个绘图项目。我的代码除了画布的撤销和重做操作外，其他都运行得很完美。我的撤销操作从paths数组列表中移除路径，并保存到undonePaths数组列表中，而重做操作则从undonePaths中移除最后一个元素，并保存到paths中。

下面是我的代码：

import java.util.ArrayList;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class DrawView extends View implements OnTouchListener {
    private Canvas  mCanvas;
    private Path    mPath;
    private Paint       mPaint;   
    private ArrayList<Path> paths = new ArrayList<Path>();
    private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

    private Bitmap im;
    public DrawView(Context context) 
    {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);      
        this.setOnTouchListener(this);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFFFFFF);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(6);
        mCanvas = new Canvas();
        mPath = new Path();
        paths.add(mPath);

        im=BitmapFactory.decodeResource(context.getResources(),R.drawable.ic_launcher);


    }               
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            //mPath = new Path();
            //canvas.drawPath(mPath, mPaint);
            for (Path p : paths){
                canvas.drawPath(p, mPaint);
            }
        }

        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 4;

        private void touch_start(float x, float y) {
            mPath.reset();
            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(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
                mX = x;
                mY = y;
            }
        }
        private void touch_up() {
            mPath.lineTo(mX, mY);
            // commit the path to our offscreen
            mCanvas.drawPath(mPath, mPaint);
            // kill this so we don't double draw            
            mPath = new Path();
            paths.add(mPath);
        }

        public void onClickUndo () { 
            if (paths.size()>0) 
            { 
               undonePaths.add(paths.remove(paths.size()-1));
               invalidate();
             }
            else
            {

            }
             //toast the user 
        }

        public void onClickRedo (){
           if (undonePaths.size()>0) 
           { 
               paths.add(undonePaths.remove(undonePaths.size()-1)); 
               invalidate();
           } 
           else 
           {

           }
             //toast the user 
        }

    @Override
    public boolean onTouch(View arg0, MotionEvent event) {
          float x = event.getX();
          float y = event.getY();

          switch (event.getAction()) {
              case MotionEvent.ACTION_DOWN:
                  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;
    }
}

这段代码在绘制方面运行良好，但在撤销和重做操作方面不完美。我的代码有什么问题？

以下是完整的源代码： http://www.4shared.com/rar/8PQQEZdH/test_draw.html 更新： 最终我的问题得到了解决，以下是我的绘图类：

import java.util.ArrayList;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class DrawView extends View implements OnTouchListener {
    private Canvas  mCanvas;
    private Path    mPath;
    private Paint       mPaint;   
    private ArrayList<Path> paths = new ArrayList<Path>();
    private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

    private Bitmap im;
    public DrawView(Context context) 
    {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);      
        this.setOnTouchListener(this);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFFFFFF);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(6);
        mCanvas = new Canvas();
        mPath = new Path();

        im=BitmapFactory.decodeResource(context.getResources(),R.drawable.ic_launcher);


    }               
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            //mPath = new Path();
            //canvas.drawPath(mPath, mPaint);
            for (Path p : paths){
                canvas.drawPath(p, mPaint);
            }
            canvas.drawPath(mPath, mPaint);
        }

        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 4;

        private void touch_start(float x, float y) {
            undonePaths.clear();
            mPath.reset();
            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(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
                mX = x;
                mY = y;
            }
        }
        private void touch_up() {
            mPath.lineTo(mX, mY);
            // commit the path to our offscreen
            mCanvas.drawPath(mPath, mPaint);
            // kill this so we don't double draw
            paths.add(mPath);
            mPath = new Path();            

        }

        public void onClickUndo () { 
            if (paths.size()>0) 
            { 
               undonePaths.add(paths.remove(paths.size()-1));
               invalidate();
             }
            else
            {

            }
             //toast the user 
        }

        public void onClickRedo (){
           if (undonePaths.size()>0) 
           { 
               paths.add(undonePaths.remove(undonePaths.size()-1)); 
               invalidate();
           } 
           else 
           {

           }
             //toast the user 
        }

    @Override
    public boolean onTouch(View arg0, MotionEvent event) {
          float x = event.getX();
          float y = event.getY();

          switch (event.getAction()) {
              case MotionEvent.ACTION_DOWN:
                  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;
    }
}

那段代码完美运行了...！

- Dinesh

Answer 1

乍一看，我看到以下问题：

- 当你添加空的 Path 到 paths 时，你立即会遇到一个问题，因为一旦你撤销，你就会先弹出那个空的 Path，使第一个撤销似乎无效。然后，如果你在那个 Path 中绘制，它不会被添加到 paths 中。解决方法是在 touch_up() 中将完成的 Path 添加到 paths 中，然后再创建一个新的 Path。

也就是说，删除

paths.add(mPath);

从构造函数开始，在 touch_up() 中更改

mPath = new Path();
paths.add(mPath);

paths.add(mPath);
mPath = new Path();

你还需要添加

canvas.drawPath(mPath, mPaint);

在onDraw()的for循环之后，添加代码以绘制正在进行中的Path。

• 当用户重新开始绘制时，您没有清空undonePaths。

- Darshan Rivka Whittle

Answer 2

请检查下面的代码，它正在运行。

package com.testpath;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.LinearLayout;

public class TesUndoPaintActivity extends Activity {
    /** Called when the activity is first created. */
    LinearLayout linearLayout2;
    private ArrayList<Path> undonePaths = new ArrayList<Path>();
    private ArrayList<Path> paths = new ArrayList<Path>();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        linearLayout2 = (LinearLayout) findViewById(R.id.linearLayout2);
        final DrawingPanel dp = new DrawingPanel(this);
        linearLayout2.addView(dp);
        ((Button) findViewById(R.id.button1))
                .setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        // TODO Auto-generated method stub
                        if (paths.size() > 0) {
                            undonePaths.add(paths
                                    .remove(paths.size() - 1));
                            dp.invalidate();
                        }
                    }
                });
        ((Button) findViewById(R.id.button2))
        .setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                 if (undonePaths.size()>0) { 
                       paths.add(undonePaths.remove(undonePaths.size()-1));
                       dp.invalidate();
                   } 
            }
        });
    }

    public class DrawingPanel extends View implements OnTouchListener {

        private Canvas mCanvas;
        private Path mPath;
        private Paint mPaint, circlePaint, outercirclePaint;

        // private ArrayList<Path> undonePaths = new ArrayList<Path>();
        private float xleft, xright, xtop, xbottom;

        public DrawingPanel(Context context) {
            super(context);
            setFocusable(true);
            setFocusableInTouchMode(true);

            this.setOnTouchListener(this);

            circlePaint = new Paint();
            mPaint = new Paint();
            outercirclePaint = new Paint();
            outercirclePaint.setAntiAlias(true);
            circlePaint.setAntiAlias(true);
            mPaint.setAntiAlias(true);
            mPaint.setColor(0xFFFFFFFF);
            outercirclePaint.setColor(0x44FFFFFF);
            circlePaint.setColor(0xAADD5522);
            outercirclePaint.setStyle(Paint.Style.STROKE);
            circlePaint.setStyle(Paint.Style.FILL);
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setStrokeJoin(Paint.Join.ROUND);
            mPaint.setStrokeCap(Paint.Cap.ROUND);
            mPaint.setStrokeWidth(6);
            outercirclePaint.setStrokeWidth(6);
            mCanvas = new Canvas();
            mPath = new Path();
            paths.add(mPath);
        }

        public void colorChanged(int color) {
            mPaint.setColor(color);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
        }

        @Override
        protected void onDraw(Canvas canvas) {

            for (Path p : paths) {
                canvas.drawPath(p, mPaint);
            }

        }

        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 0;

        private void touch_start(float x, float y) {
            mPath.reset();
            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(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
                mX = x;
                mY = y;
            }
        }

        private void touch_up() {
            mPath.lineTo(mX, mY);
            // commit the path to our offscreen
            mCanvas.drawPath(mPath, mPaint);
            // kill this so we don't double draw
            mPath = new Path();
            paths.add(mPath);
        }

        @Override
        public boolean onTouch(View arg0, MotionEvent event) {
            float x = event.getX();
            float y = event.getY();

            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // if (x <= cx+circleRadius+5 && x>= cx-circleRadius-5) {
                // if (y<= cy+circleRadius+5 && cy>= cy-circleRadius-5){
                // paths.clear();
                // return true;
                // }
                // }
                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;
        }
    }
}

以下是XML文件内容。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Undo" />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Redo" />

    </LinearLayout>


    <LinearLayout
        android:id="@+id/linearLayout2"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >

    </LinearLayout>

</LinearLayout>

请检查它。

- Nikhil

---

你的代码完美地运作了，但有一个问题。第一次点击“撤销”按钮时，它并没有撤销上一步操作。你知道如何解决这个问题吗？ - Dinesh

+1，感谢您的努力，佩服！很抱歉，您的代码一直在工作，但是出现了一些问题，我从@Darshan Computing那里找到了答案。 - Dinesh

Answer 3

问题

绘制路径时，路径只有在完成绘制后才显示出来，这让用户不知道他正在画什么。

解决方案

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

   for (Path p : paths){
        canvas.drawPath(p, mPaint);
    }

    //Draw path along with the finger
    canvas.drawPath(mPath, mPaint);
}

将canvas.drawPath(mPath,mPaint)添加到onDraw()中，这样用户就能感觉自己真的在画布上作画了。

- Shivm

---

这是作为答案发布的，但它并没有回答问题的任何部分。（而且已经有被接受的答案解决了这个问题。） - Darshan Rivka Whittle