android paint 回滚重做

翻译于 2013-06-20 14:35:48 发布 · 419 阅读

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本文介绍了一个基于Android平台的绘图视图(DrawView)实现方法。该视图支持触摸绘制，并提供了撤销与重做功能。文章详细展示了如何通过Canvas、Path及Paint等组件进行路径绘制，同时利用ArrayList存储绘制路径以便于撤销操作。

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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;
    }
}