ImageView Drag Limitation In Android

Question

I have an ImageView in a layout and set OnTouchListener on ImageView to drag the ImageView. It\'s working perfectly. My problem is how can I prevent from move ImageView to out o

Answer 1

Add the following parameters to the Touch class:

private float dx; // postTranslate X distance
private float dy; // postTranslate Y distance
private float[] matrixValues = new float[9];
float matrixX = 0; // X coordinate of matrix inside the ImageView
float matrixY = 0; // Y coordinate of matrix inside the ImageView
float width = 0; // width of drawable
float height = 0; // height of drawable

Modify your code after case MotionEvent.ACTION_MOVE:

if (mode == DRAG) {
        matrix.set(savedMatrix);

        matrix.getValues(matrixValues);
        matrixX = matrixValues[2];
        matrixY = matrixValues[5];
        width = matrixValues[0] * (((ImageView) view).getDrawable()
                                .getIntrinsicWidth());
        height = matrixValues[4] * (((ImageView) view).getDrawable()
                                .getIntrinsicHeight());

        dx = event.getX() - start.x;
        dy = event.getY() - start.y;

        //if image will go outside left bound
        if (matrixX + dx < 0){
            dx = -matrixX;
        }
        //if image will go outside right bound
        if(matrixX + dx + width > view.getWidth()){
            dx = view.getWidth() - matrixX - width;
        }
        //if image will go oustside top bound
        if (matrixY + dy < 0){
            dy = -matrixY;
        }
        //if image will go outside bottom bound
        if(matrixY + dy + height > view.getHeight()){
            dy = view.getHeight() - matrixY - height;
        }
        matrix.postTranslate(dx, dy);   
    }