canvas.translate in android put space on both side after translating

Question

I want to scale and translate the custom list view. i have done successfully zooming but when i move horizontally after scaling,it goes beyond screen width (means i see white screen )and when i move horizontally in opposite side i again see the view.

problem is that after using canvas.translate(x,0) only in x direction it is not fixed upto view width

this is the code which i used-

public class CustomListView extends ListView{

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
private float x = 0;
private float y = 0;
private float startx = 0;
private float starty = 0;
private boolean canClick = true;
private float xtranslation = 0;
private float xPos = 0;


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

@Override
public boolean onTouchEvent(MotionEvent ev) {
    if (ev.getAction() == MotionEvent.ACTION_DOWN) {
        startx = ev.getX();
        starty = ev.getY();
    }

    if (ev.getPointerCount() > 1) {
        y = ev.getY();
        x = ev.getX();
    } else if (ev.getAction() == MotionEvent.ACTION_UP) {
        canClick = (ev.getX() - startx) == 0 && (ev.getY() - starty) == 0 && mScaleFactor == 1;
    } else if((ev.getAction() == MotionEvent.ACTION_MOVE)){
        xtranslation = ev.getX() - startx;
    }      
    mScaleDetector.onTouchEvent(ev);
    return super.onTouchEvent(ev);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.scale(mScaleFactor, mScaleFactor, x , y);
    System.out.println("trans : "+xtranslation+"   XPOS : "+xPos);
    if(mScaleFactor > 1){
        canvas.translate(xtranslation/2, 0);
    }
    super.onDraw(canvas);
}

private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener{
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
         canClick = false;
            mScaleFactor *= detector.getScaleFactor();

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 2.0f));

            if (mScaleFactor <= 1) {
                mScaleFactor = 1;
                canClick = true;
            }

            xPos = CustomListView.this.getWidth() - detector.getFocusX();

            CustomListView.this.invalidate();
            return true;
    }
}
public boolean canClick(){
    return canClick;
}

}

please solve my problem if possible