Android Canvas撤消和重做位图

我在撤消和重做操作上遇到了问题。我注意到下面的代码工程，如果我不使用canvas.drawbitmap在Ondraw（）方法，但我需要绘制到位图，所以我可以保存画布图像，以及加载图像。请帮助我。以下是我的代码。Android Canvas撤消和重做位图

import java.util.ArrayList; 

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.Bitmap.Config; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Paint.Cap; 
import android.graphics.Paint.Join; 
import android.graphics.Paint.Style; 
import android.graphics.Path; 
import android.graphics.PorterDuff.Mode; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.view.View; 

import com.akinslove.drawingapp.activities.DrawingCanvasActivity; 

public class DrawView extends View { 

    // for bitmap 
    private Bitmap mainBitmap; 
    private Canvas mainCanvas; 
    private Paint mainbitmapPaint; 

    // for canvas 
    private Path currentPath; 
    private Paint currentpathPaint; 


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

    public DrawView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
     initialiseMyComponents(); 
    } 

    public DrawView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     initialiseMyComponents(); 
    } 

    public DrawView(Context context) { 
     super(context); 
     initialiseMyComponents(); 
    } 

    private void initialiseMyComponents() { 
     currentPath = new Path(); 

     currentpathPaint = new Paint(); 
     currentpathPaint.setColor(Color.BLACK); 
     currentpathPaint.setStrokeWidth(10); 
     currentpathPaint.setStyle(Style.STROKE); 
     currentpathPaint.setStrokeJoin(Join.ROUND); 
     currentpathPaint.setStrokeCap(Cap.ROUND); 
     currentpathPaint.setAntiAlias(true); 

     mainbitmapPaint = new Paint(); 
    } 

    @Override 
    protected void onDraw(Canvas canvas) { 

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

      **//I wish to use the below line of code 
      canvas.drawBitmap(mainBitmap, 0, 0, mainbitmapPaint);** 
    } 

    @Override 
    protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
     if (mainBitmap == null) { 
      mainBitmap = Bitmap.createBitmap(w, h, Config.ARGB_8888); 
      mainCanvas = new Canvas(mainBitmap); 
      mainCanvas.drawColor(Color.WHITE); 
     } 
    } 

    float lastX; 
    float lastY; 

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

     switch (action) { 
     case MotionEvent.ACTION_DOWN: 
      undonePaths.clear(); 


      DrawingCanvasActivity.IMAGEDRAWN = true; 
      currentPath.moveTo(x, y); 
      lastX = x; 
      lastY = y; 
      invalidate(); 
      break; 
     case MotionEvent.ACTION_MOVE: 
      currentPath.quadTo(lastX, lastY, (lastX + x)/2, (lastY + y)/2); 
      mainCanvas.drawPath(currentPath, currentpathPaint); 
      lastX = x; 
      lastY = y; 
      invalidate(); 
      break; 
     case MotionEvent.ACTION_UP: 
      currentPath.lineTo(x, y); 
      mainCanvas.drawPath(currentPath, currentpathPaint); 

        // kill this so we don't double draw 
        paths.add(currentPath); 
        currentPath = new Path(); 

      currentPath.rewind(); 
      invalidate(); 
      break; 
     } 

     return true; 
    } 



    // method to get bitmap 
    public Bitmap getMainBitmap() { 
     return mainBitmap; 
    } 

    // method to set bitmap 
    public void setMainBitmap(Bitmap mpt) { 
     mainBitmap = mpt; 
     mainCanvas = new Canvas(mainBitmap); 
     postInvalidate(); 

    } 

    public void onClickUndo() { 

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

    public void onClickRedo(){ 

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

来源

2013-10-30 Akinslove

我刚刚发现，在两个case MotionEvent.ACTION_UP:和case MotionEvent.ACTION_MOVE:行mainCanvas.drawPath(currentPath, currentpathPaint);不应该存在。它似乎将路径重绘为位图并放到画布上。不知道我说的是正确的android条款。

来源

2013-10-30 16:19:14 Akinslove

Android Canvas撤消和重做位图

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