Android - 画布混乱(绘图和滚动)

时间:2013-02-27 16:53:08

标签: android android-canvas

我对android中的canvas感到有些困惑,并且想知道是否有人可以为我澄清一些事情。

我目前在View类中有这个代码:

 class HomerView extends View { // the custom View for drawing on
    // set up Bitmap, canvas, path and paint
    private Bitmap myBitmap; // the initial image we turn into our canvas
    private Canvas myCanvas; // the canvas we are drawing on
    private Rect myRect; // the mathematical path of the lines we draw
    private Paint myBitmapPaint; // the paint we use to draw the bitmap

    // get the width of the entire tablet screen
    private int screenWidth = getContext().getResources()
            .getDisplayMetrics().widthPixels;
    // get the height of the entire tablet screen
    private int screenHeight = getContext().getResources()
            .getDisplayMetrics().heightPixels;

    private int mX, mY, iX, iY; // current x,y and initial x,y
    private static final float TOUCH_TOLERANCE = 4;
    private static final int INVALID_POINTER_ID = -1;
    private float mPosX;
    private float mPosY;
    private BitmapDrawable mImage;
    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;
    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;

    public HomerView(Context context) { // constructor of HomerView
        super(context);
        myBitmap = Bitmap.createBitmap(screenWidth, screenHeight,
                Bitmap.Config.ARGB_8888); // set our drawable space - the bitmap which becomes the canvas we draw on
        myCanvas = new Canvas(myBitmap); // set our canvas to our bitmap which we just set up
        myRect = new Rect(); // make a new rect
        myBitmapPaint = new Paint(Paint.DITHER_FLAG); // set dither to ON in our saved drawing - gives better color interaction
        setHorizontalScrollBarEnabled(true);
        setVerticalScrollBarEnabled(true);
        TypedArray a = context.obtainStyledAttributes(R.styleable.View);
        initializeScrollbars(a);
        a.recycle();
        computeVerticalScrollRange();
        computeHorizontalScrollRange();
        mImage = new BitmapDrawable(getResources(), myBitmap);
        mScaleDetector = new ScaleGestureDetector(context,
                new ScaleListener());
    }

    public HomerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScaleDetector = new ScaleGestureDetector(context,
                new ScaleListener());
    }

    public HomerView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    protected void onDraw(Canvas canvas) { // method used when we want to draw something to our canvas
        super.onDraw(canvas);
        if (addObjectMode == true) {
            canvas.drawColor(Color.TRANSPARENT); // sets canvas colour
            canvas.drawBitmap(myBitmap, 0, 0, myBitmapPaint); // save the canvas to bitmap - the numbers are the x, y coords we are drawing from
            canvas.drawRect(myRect, myPaint); // draw the rectangle that the user has drawn using the paint we set up
        } else if (moveMode == true) {
            canvas.save();
            System.out.println("X: " + mPosX + " Y: " + mPosY);
            canvas.translate(mPosX, mPosY);
            canvas.scale(mScaleFactor, mScaleFactor);
            mImage.draw(canvas);
            canvas.restore();
        }

根据我的理解,这是两种不同的绘制到屏幕的方法的合并。我的理解是我有myBitmap(这是用户绘图的用法),这适用于“addObjectMode”。但是,“moveMode”是指我希望用户能够在他们绘制的房屋计划周围捏缩放滚动等。

目前,我可以很好地绘制对象,但是当我按下按钮启用moveMode时,当我触摸或手势时,绘图会消失。我知道这可能是因为onDraw()中的代码;但帆布对我来说仍然有点神秘。

最终,我将需要一个基本的撤消/重做功能,并保存稍后要打开的canvas/bitmap。任何人都可以提供任何建议或链接到任何全面的画布教程吗?

编辑:包含我的onTouchEvent方法可能也很有用 -

 public boolean onTouchEvent(MotionEvent event) { // on any touch event
        if (addObjectMode == true) {

            float x = event.getX(); // get current X
            float y = event.getY(); // get current Y

            switch (event.getAction()) { // what action is the user performing?
            case MotionEvent.ACTION_DOWN: // if user is touching down
                touch_Start(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE: // if user is moving finger while touched down
                touch_Move(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_UP: // if user has released finger
                touch_Up();
                invalidate();
                break;
            }
            return true;
        } else if (moveMode == true) {
            mScaleDetector.onTouchEvent(event);
            final int action = event.getAction();
            switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN: {
                final float x = event.getX();
                final float y = event.getY();
                mLastTouchX = x;
                mLastTouchY = y;
                mActivePointerId = event.getPointerId(0);
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                final int pointerIndex = event
                        .findPointerIndex(mActivePointerId);
                final float x = event.getX(pointerIndex);
                final float y = event.getY(pointerIndex);

                // Only move if the ScaleGestureDetector isn't processing a gesture.
                if (!mScaleDetector.isInProgress()) {
                    final float dx = x - mLastTouchX;
                    final float dy = y - mLastTouchY;
                    mPosX += dx;
                    mPosY += dy;
                    invalidate();
                }
                mLastTouchX = x;
                mLastTouchY = y;
                break;
            }

            case MotionEvent.ACTION_UP: {
                mActivePointerId = INVALID_POINTER_ID;
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                mActivePointerId = INVALID_POINTER_ID;
                break;
            }

            case MotionEvent.ACTION_POINTER_UP: {
                final int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int pointerId = event.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    // This was our active pointer going up. Choose a new
                    // active pointer and adjust accordingly.
                    final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                    mLastTouchX = event.getX(newPointerIndex);
                    mLastTouchY = event.getY(newPointerIndex);
                    mActivePointerId = event.getPointerId(newPointerIndex);
                }
                break;
            }
            }
            return true;
        } else {
            return false;
        }
    }

3 个答案:

答案 0 :(得分:1)

在您的示例中,当您在moveMode中时,您不会在最终画布上绘制任何内容。

即使您正在对已绘制的内容应用转换,请注意两次调用onDraw()之间的画布是清晰的,因此您可以再次绘制它。

我不熟悉撤消重做功能,但您应该能够在给定点存储画布位图的副本以便以后恢复

Bitmap.copy()

请注意,存储大量位图对于移动环境来说可能非常繁重,因此您必须限制撤消堆栈大小。

答案 1 :(得分:0)

删除draw方法的if else if条件,对于undo功能,创建位图的arraylist,并在每次用户执行某些操作时保存位图,然后在undo上将位图替换为previous并使视图无效

答案 2 :(得分:0)

为了实现Undo \ Redo,您需要维护路径列表...并且必须相应地将这些路径存储在路径列表中。我已经在下面附上了我的代码,看看它然后你会得到一些关于撤销重做功能的明确想法。

     public static LinkedList<Path> rrPathList=new LinkedList<Path>();
     public static LinkedList<Path> mPathList=new LinkedList<Path>();
     protected void onDraw(Canvas canvas) {

            for( i = 0; i < mPathList.size() && i < sPaint.size(); i++ )
            {
                canvas.drawPath(mPathList.get(i),sPaint.get(i));

            }
          }
   // In your touch up method store the paths into mPathList
        private void touch_up() {     
            mCanvas.drawPath(mPath, mPaint);
            mPathList.add(mPath);  
        }
   // Undo function
     public void undo()
    {
        try
        {
            if(mPathList.size()>0)
            {
                rPathList.add(mPathList.getLast());
                mPathList.removeLast();

                 invalidate();
            }
        }catch(ArrayIndexOutOfBoundsException arr)
        {
          //Print error;
        }
    }
     // Redo function
     public void redo()
    {
        try
        {
            if(rPathList.size()>0)
            {
                mPathList.add(rPathList.getLast());
                rPathList.removeLast();
             invalidate();
            }
        }catch(ArrayIndexOutOfBoundsException arr)
        {
            //Handle error
        }
    }

注意:请不要忘记调用“invalidate()”。 调用invalidate results“调用画布并重绘mPathList对象” 试试这个。我正在使用这段代码...... 谢谢!!!

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