Comment implémenter annuler, rétablir et effacer dans le canevas Android

Question

Je veux créer un projet comme dessin qui est nécessaire pour prendre en charge le dessin, annuler, rétablir et effacer. L'effaceur doit supprimer uniquement pour la vue de dessin et non pour supprimer l'arrière-plan. Le code ci-dessous implémente les fonctions d'annulation et de rétablissement. Je veux ajouter l'option gomme mais ce n'est pas fait. Comment mettre en œuvre l'option gomme en utilisant le code ci-dessous?

 import android.content.Context; 
     import android.graphics.Bitmap; 
     import android.graphics.Canvas; 
     import android.graphics.Color; 
     import android.graphics.Paint; 
     import android.graphics.Path; 
     import android.util.AttributeSet; 
     import android.view.MotionEvent; 


     import java.util.ArrayList; 


     public class CanvasView extends View { 


     private Paint mPenPainter; 
     public int width; 

     public int height; 


     private Bitmap mBitmap; 
     private Canvas mCanvas; 

     private Path mPath; 

     Context context; 

     private Paint mPaint; 

     private float mX, mY; 

     private static final float TOLERANCE = 5; 
     private ArrayList<Path> paths = new ArrayList<Path>(); 
     private ArrayList<Path> undonePaths = new ArrayList<Path>(); 


     private int paintColor = 0xFF000000; 

     public CanvasView(Context c, AttributeSet attrs) { 

     super(c, attrs); 

     context = c; 


     // we set a new Path 

     mPath = new Path(); 


     // and we set a new Paint with the desired attributes 

     mPaint = new Paint(); 

     mPaint.setAntiAlias(true); 

     mPaint.setColor(paintColor); 

     mPaint.setStyle(Paint.Style.STROKE); 

     mPaint.setStrokeJoin(Paint.Join.ROUND); 

     mPaint.setStrokeWidth(4f); 


     //float mEraserWidth = getResources().getDimension(R.dimen.eraser_size); 
     mPenPainter = new Paint(); 
     mPenPainter.setColor(Color.BLUE); 

     } 


     // override onSizeChanged 
     @Override 

     protected void onSizeChanged(int w, int h, int oldw, int oldh) { 

     super.onSizeChanged(w, h, oldw, oldh); 


     // your Canvas will draw onto the defined Bitmap 

     mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); 

     mCanvas = new Canvas(mBitmap); 

     } 


     // override onDraw 

     @Override 

     protected void onDraw(Canvas canvas) { 

     super.onDraw(canvas); 
     // draw the mPath with the mPaint on the canvas when onDraw 
     for (Path p : paths) { 
     canvas.drawPath(p, mPaint); 
     } 
     canvas.drawPath(mPath, mPaint); 
     // paths.add(mPath); 

     } 

     private void startTouch(float x, float y) { 

     undonePaths.clear(); 
     mPath.reset(); 
     mPath.moveTo(x, y); 

     mX = x; 

     mY = y; 
     } 

     public void onClickUndo() { 
     if (paths.size() > 0) { 
     undonePaths.add(paths.remove(paths.size() - 1)); 
     invalidate(); 
     } else { 
     //Util.Imageview_undo_redum_Status=false; 
     } 
     //toast the user 
     } 

     public void onClickRedo() { 
     if (undonePaths.size() > 0) { 
     paths.add(undonePaths.remove(undonePaths.size() - 1)); 
     invalidate(); 
     } else { 
     // Util.Imageview_undo_redum_Status=false; 
     } 
     //toast the user 
     } 

     // when ACTION_MOVE move touch according to the x,y values 

     private void moveTouch(float x, float y) { 

     float dx = Math.abs(x - mX); 

     float dy = Math.abs(y - mY); 

     if (dx >= TOLERANCE || dy >= TOLERANCE) { 

     mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 

     mX = x; 

     mY = y; 

     } 
     } 


     private void upTouch() { 


     mPath.lineTo(mX, mY); 

     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(); 
     } 


     //override the onTouchEvent 

     @Override 

     public boolean onTouchEvent(MotionEvent event) { 

     float x = event.getX(); 

     float y = event.getY(); 
     float mCurX; 
     float mCurY; 

     switch (event.getAction()) { 

     case MotionEvent.ACTION_DOWN: 


     mX = event.getX(); 

     mY = event.getY(); 


     startTouch(x, y); 
     invalidate(); 

     break; 

     case MotionEvent.ACTION_MOVE: 


     moveTouch(x, y); 

     invalidate(); 

     break; 

     case MotionEvent.ACTION_UP: 

     upTouch(); 
     invalidate(); 

     break; 
     } 

     return true; 

     } 

Answer 1

Je pense que vous devriez utiliser ce modèle: https://sourcemaking.com/design_patterns/command

Je l'ai utilisé pour mon application à utiliser undo/redo

Answer 2

pour vous effacer besoin de savoir Intersection entre la sélection actuelle et tracer des chemins . reportez-vous ci-dessous le code

package opensourcecode.com.paginationwebview; 

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Path; 
import android.graphics.Point; 
import android.graphics.RectF; 
import android.support.annotation.Nullable; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.View; 

import java.util.ArrayList; 

/** 
* Created by damodhar.meshram on 4/26/2017. 
*/ 

public class CanvasView extends View { 
    private Paint mPenPainter; 
    public int width; 

    public int height; 


    private Bitmap mBitmap; 
    private Canvas mCanvas; 

    private Path mPath; 

    Context context; 

    private Paint mPaint; 

    private float mX, mY; 

    private static final float TOLERANCE = 5; 
    private ArrayList<Path> paths = new ArrayList<Path>(); 
    private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

    private boolean isErasemode = false; 

    private int paintColor = 0xFF000000; 

    public CanvasView(Context c, AttributeSet attrs) { 

     super(c, attrs); 

     context = c; 


     // we set a new Path 

     mPath = new Path(); 


     // and we set a new Paint with the desired attributes 

     mPaint = new Paint(); 

     mPaint.setAntiAlias(true); 

     mPaint.setColor(paintColor); 

     mPaint.setStyle(Paint.Style.STROKE); 

     mPaint.setStrokeJoin(Paint.Join.ROUND); 

     mPaint.setStrokeWidth(4f); 


     //float mEraserWidth = getResources().getDimension(R.dimen.eraser_size); 
     mPenPainter = new Paint(); 
     mPenPainter.setColor(Color.BLUE); 

    } 

    public CanvasView(Context c) { 

     super(c); 

     context = c; 


     // we set a new Path 

     mPath = new Path(); 


     // and we set a new Paint with the desired attributes 

     mPaint = new Paint(); 

     mPaint.setAntiAlias(true); 

     mPaint.setColor(paintColor); 

     mPaint.setStyle(Paint.Style.STROKE); 

     mPaint.setStrokeJoin(Paint.Join.ROUND); 

     mPaint.setStrokeWidth(4f); 


     //float mEraserWidth = getResources().getDimension(R.dimen.eraser_size); 
     mPenPainter = new Paint(); 
     mPenPainter.setColor(Color.BLUE); 

    } 


    // override onSizeChanged 
    @Override 

    protected void onSizeChanged(int w, int h, int oldw, int oldh) { 

     super.onSizeChanged(w, h, oldw, oldh); 


     // your Canvas will draw onto the defined Bitmap 

     mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); 

     mCanvas = new Canvas(mBitmap); 

    } 


    // override onDraw 

    @Override 

    protected void onDraw(Canvas canvas) { 

     super.onDraw(canvas); 
     // draw the mPath with the mPaint on the canvas when onDraw 
     for (Path p : paths) { 
      canvas.drawPath(p, mPaint); 
     } 
     canvas.drawPath(mPath, mPaint); 
     // paths.add(mPath); 

    } 

    private void startTouch(float x, float y) { 

     undonePaths.clear(); 
     mPath.reset(); 
     mPath.moveTo(x, y); 

     mX = x; 

     mY = y; 
    } 

    public void onClickUndo() { 
     if (paths.size() > 0) { 
      undonePaths.add(paths.remove(paths.size() - 1)); 
      invalidate(); 
     } else { 
      //Util.Imageview_undo_redum_Status=false; 
     } 
     //toast the user 
    } 

    public void onEraser(){ 
     if(!isErasemode){ 
      isErasemode = true; 
     }else{ 
      isErasemode = false; 
     } 
    } 

    private void remove(int index){ 
     paths.remove(index); 
     invalidate(); 
    } 

    public void onClickRedo() { 
     if (undonePaths.size() > 0) { 
      paths.add(undonePaths.remove(undonePaths.size() - 1)); 
      invalidate(); 
     } else { 
      // Util.Imageview_undo_redum_Status=false; 
     } 
     //toast the user 
    } 

    // when ACTION_MOVE move touch according to the x,y values 

    private void moveTouch(float x, float y) { 

     float dx = Math.abs(x - mX); 

     float dy = Math.abs(y - mY); 

     if (dx >= TOLERANCE || dy >= TOLERANCE) { 

      mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 

      mX = x; 

      mY = y; 

     } 
    } 


    private void upTouch() { 


     mPath.lineTo(mX, mY); 

     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(); 
    } 


    //override the onTouchEvent 

    @Override 

    public boolean onTouchEvent(MotionEvent event) { 

     float x = event.getX(); 

     float y = event.getY(); 
     float mCurX; 
     float mCurY; 

     if(isErasemode){ 

      for(int i = 0;i<paths.size();i++){ 
       RectF r = new RectF(); 
       Point pComp = new Point((int) (event.getX()), (int) (event.getY())); 

       Path mPath = paths.get(i); 
       mPath.computeBounds(r, true); 
       if (r.contains(pComp.x, pComp.y)) { 
        Log.i("need to remove","need to remove"); 
        remove(i); 
        break; 
       } 
      } 
      return false; 
     }else { 

      switch (event.getAction()) { 

       case MotionEvent.ACTION_DOWN: 


        mX = event.getX(); 

        mY = event.getY(); 


        startTouch(x, y); 
        invalidate(); 

        break; 

       case MotionEvent.ACTION_MOVE: 


        moveTouch(x, y); 

        invalidate(); 

        break; 

       case MotionEvent.ACTION_UP: 

        upTouch(); 
        invalidate(); 

        break; 
      } 

      return true; 
     } 

    } 
}