The following is the code I used in the app I am working
You will have to use the OnScrollChanged
function in your ScrollView
. ActionBar
doesn't let you set the opacity , so set a background drawable on the actionbar and you can change its opacity based on the amount of scroll in the scrollview. I have given an example workflow
The function sets gives the appropriate alpha for the view locationImage based on its position WRT window .
this.getScrollY()
gives you how much the scrollView
has scrolled
public void OnScrollChanged(int l, int t, int oldl, int oldt) {
// Code ...
locationImage.setAlpha(getAlphaForView(locationImageInitialLocation- this.getScrollY()));
}
private float getAlphaForView(int position) {
int diff = 0;
float minAlpha = 0.4f, maxAlpha = 1.f;
float alpha = minAlpha; // min alpha
if (position > screenHeight)
alpha = minAlpha;
else if (position + locationImageHeight < screenHeight)
alpha = maxAlpha;
else {
diff = screenHeight - position;
alpha += ((diff * 1f) / locationImageHeight)* (maxAlpha - minAlpha); // 1f and 0.4f are maximum and min
// alpha
// this will return a number betn 0f and 0.6f
}
// System.out.println(alpha+" "+screenHeight +" "+locationImageInitialLocation+" "+position+" "+diff);
return alpha;
}
EDIT : I have added an example working sample at https://github.com/ramanadv/fadingActionBar , you can have a look at it.