ImageBoard.java

public class ImageBoard extends View {

    RectF mCurrentViewPort;
    Rect mContentRect;
    ImageView image;
    int width;
    int height;

    int dragedWidth = 0;
    int dragedHeight = 0;

    int dx = 0;
    int dy = 0;

    Paint boarderPaint;

    int drawableWidth;
    int drawableHeight;

    Drawable src;

    //GestureDetector gd;
    GestureDetectorCompat gdc;


    public ImageBoard(Context context){
        //this(context, null, 0);
        super(context);

    }

    public ImageBoard(Context context, AttributeSet attrs){
        //this(context, attrs, 0);
        super(context, attrs);
        init(context, attrs);
    }

    public ImageBoard(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {

        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public ImageBoard(Context context, @Nullable AttributeSet attrs,
                      int defStyleAttr, int defStyleRes){
        super(context, attrs, defStyleAttr, defStyleRes);
        init(context, attrs);
    }



    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        width = w;
        height = h;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){

        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        int desiredWidth = 300;
        int desiredHeight = 300;

        int width;
        int height;

        //width
        if(widthMode == MeasureSpec.EXACTLY){
            //Must be this size
            width = widthSize;

        }else if(widthMode == MeasureSpec.AT_MOST){
            //Can't be bigger than...
            width = Math.min(widthSize, desiredWidth);

        }else{
            //Be whatever you want
            width = desiredWidth;
        }

        //height
        if(heightMode == MeasureSpec.EXACTLY){
            //Must be this size
            height = heightSize;

        }else if(heightMode == MeasureSpec.AT_MOST){
            //Can't be bigger than...
            height = Math.min(heightSize, desiredHeight);

        }else{
            //Be whatever you want
            height = desiredHeight;
        }

        //MUST CALL THIS
        setMeasuredDimension(width, height);
    }

    public void init(Context context, @Nullable AttributeSet attrs){

        //gd = new GestureDetector(context, mGestureListener);
        gdc = new GestureDetectorCompat(context, new MyGestureListener());
        mCurrentViewPort = new RectF();
        mContentRect = new Rect();

        boarderPaint = new Paint();
        boarderPaint.setColor(Color.BLUE);
        boarderPaint.setStyle(Paint.Style.STROKE);
        boarderPaint.setStrokeWidth(20);

        TypedArray ta = context.
                obtainStyledAttributes(attrs, R.styleable.ImageBoard, 0, 0);
        try{

            src = (Drawable) ta.getDrawable(R.styleable.ImageBoard_src);

            drawableWidth = src.getIntrinsicWidth();
            drawableHeight = src.getIntrinsicHeight();
        }catch(Exception ex){
            Toast.makeText(context, "Error: " + ex.toString(),
                    Toast.LENGTH_LONG + 3000).show();
        }
        finally {
            ta.recycle();
        }

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        mContentRect.left = (int) dx;
        mContentRect.top = (int)  dy;
        mContentRect.right = (int) dx + drawableWidth;
        mContentRect.bottom = (int) dy + drawableHeight;

        mCurrentViewPort.left = 0;
        mCurrentViewPort.top = 0;
        mCurrentViewPort.right = width;
        mCurrentViewPort.bottom = height;

        if(src != null)
        {
            src.setBounds(mContentRect);
            src.draw(canvas);
        }

        canvas.drawRect(mCurrentViewPort, boarderPaint);



    }

    class MyGestureListener extends GestureDetector.SimpleOnGestureListener{

        @Override
        public boolean onDown(MotionEvent e){

            return  true;
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                                float distanceX, float distanceY){

            dx -= (int) distanceX;
            dy -= (int) distanceY;
            ImageBoard.this.invalidate();

            return true;
        }

    }


    @Override
    public boolean onTouchEvent(MotionEvent e){
         this.gdc.onTouchEvent(e);
       // return super.onTouchEvent(e);
        return true;
    }



    }