android - 在 Canvas 上绘制的多种颜色

Question

我正在尝试在 Canvas 上绘制多种颜色，初始颜色效果很好，但是当它切换到另一种颜色时，线条是用以前的颜色绘制的，但是后续线条是用正确的颜色绘制的。即如果我从绿色切换到黑色，我绘制的下一条线是绿色，但从那时起它是黑色的。任何帮助表示赞赏。

public class DrawingPanel extends View implements OnTouchListener {
    private static final String TAG = "DrawView";
    private static final float MINP = 0.25f;
    private static final float MAXP = 0.75f;
    private Canvas  mCanvas;
    private Path    mPath;
    private Paint   mPaint; 
    private Paint   bmPaint;
    private Paint   gmPaint;
    private ArrayList<Path> paths = new ArrayList<Path>();
    private Map<Path, Integer> colorsMap = new HashMap<Path,Integer>();
    private int selectedcolor;
    SharedPreferences settings= getSharedPreferences("Macaroni",0);
    private String selColr = settings.getString("DrawColor", "");

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

        this.setOnTouchListener(this);

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(Color.BLACK);
        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);
         colorsMap.put(mPath,getColorSel());

    }               
        @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){

                int grabColorFromHash =colorsMap.get(p);    
                mPaint.setColor(grabColorFromHash);
                 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;
            Log.i("touch_start","touch_start");
           }

    private void touch_move(float x, float y) {
            float dx = Math.abs(x - mX);
            float dy = Math.abs(y - mY);
            Log.i("touch_move","touch_move");

            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);
            mPath = new Path();
            paths.add(mPath);
            colorsMap.put(mPath,getColorSel());
            mPaint.setColor(getColorSel());

        }
    public int getColorSel() 
    {

            selColr = settings.getString("DrawColor", "");

         if (selColr.equalsIgnoreCase("Black")){
            mPaint.setColor(Color.BLACK);
            selectedcolor = mPaint.getColor();
           }

           if (selColr.equalsIgnoreCase("Red"))
           { 
            mPaint.setColor(Color.RED);
            selectedcolor = mPaint.getColor();
           }

           if (selColr.equalsIgnoreCase("Green"))
           { 
            mPaint.setColor(Color.GREEN);
            selectedcolor = mPaint.getColor();
           }

        return selectedcolor;

    }
    @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;
    }
}

Answer 1

在您的 touch_start 中，您重置了路径，但直到 touch_up 才将其添加到 ArrayList，因此当您四处拖动手指时，我根本看不到它是如何绘制的。

您的 onDraw 仅在遍历 ArrayList 时绘制路径。换句话说，将一些代码添加到 onDraw 以绘制 mPath 以及所有已保存在 ArrayList 中的代码。

如果不能在调试器中运行你的东西很难说，但我认为这可能会解决你的问题。