这是在 Android Canvas 中实现撤消和重做的代码，运行良好。

package com.example.canva;

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


public class MainView extends View {
private Canvas  mCanvas;
private Path    mPath;

private Paint       mPaint;   
private ArrayList<Path> paths = new ArrayList<Path>();
private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

public MainView(Context context) 
{
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);      
    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 onTouchEvent(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;
    }
   }

但在我的应用程序中，我需要更改颜色、笔划宽度、样式等。当我尝试使用以下方法更改颜色时， Canvas 中的整个内容都会更改为该颜色。

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

最佳答案

将路径保存在数组中并对该数组执行操作以撤消或重做。

关于android - 颜色选择器不适用于撤消和重做，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30659441/