How to make a ActionBar like Google Play that fades in when scrolling

Question

How to make transparent or translucent ActionBar like Google Play that fades in or out when scrolling using windowActionBarOverlay?

Check the f

Answer 1

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.

Answer 2

If you are using a CoordinatorLayout in your layout xml you should checkout this article describing how to handle scrolls and make other views react to them.

There is an example accomplishing what you asked for, if you add your imageview as a child of the CollapsingToolbarLayout all the magic is handled automatically and you can even some parameters like the scrim color, minimum height to start collapsing, etc:

Answer 3

On webView:

@JavascriptInterface
public void showToolbar(String scrollY, String imgWidth) {
    int int_scrollY = Integer.valueOf(scrollY);
    int int_imgWidth = Integer.valueOf(imgWidth);

    String clr;
    if (int_scrollY<=int_imgWidth-actionBarHeight) {
        clr = Integer.toHexString(int_scrollY * 255 / (int_imgWidth-actionBarHeight));
    }else{
        clr = Integer.toHexString(255);
    }

    toolbar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#"+clr+"9CCC65")));
}

Answer 4

Using AbsListView scroll listener we can achieve for listview simply without using other complicated library or ScrollView

set scroll listener to list view

public class PagedScrollListener implements AbsListView.OnScrollListener {
    private ActionBar mActionBar;
    private View mTopHideView; // represent header view

     @Override
    public void onScrollStateChanged(final AbsListView view, final int scrollState) {
        mScrollState = scrollState;
    }

    @Override
    public void onScroll(final AbsListView view, final int firstVisibleItem, final int visibleItemCount, final int totalItemCount) {

        if (mActionBar != null && mTopHideView != null && mListView != null) {
            Log.i(TAG, getScrollY() + "");
            int currentY = getScrollY();

            final int headerHeight = mTopHideView.getHeight() - mActionBar.getHeight();
            final float ratio = (float) Math.min(Math.max(currentY, 0), headerHeight) / headerHeight;
            final int newAlpha = (int) (ratio * 255);
            Log.i(TAG, newAlpha + " alpha");
            mActionBarDrawaqble.setAlpha(newAlpha);
}}


public void setActionBarRefernce(ActionBar actionBar, View topHideView, float actionBarHeight, ListView listView) {
        mActionBar = actionBar;
        mActionBarHeight = actionBarHeight;
        mTopHideView = topHideView;
        mListView = listView;
        mActionBarDrawaqble = new ColorDrawable(ContextCompat.getColor(mContext, R.color.google_plus_red));
        mActionBar.setBackgroundDrawable(mActionBarDrawaqble);
        mActionBarDrawaqble.setAlpha(0);
    }

   public int getScrollY() {
        View c = mListView.getChildAt(0);
        if (c == null) {
            return 0;
        }

        int firstVisiblePosition = mListView.getFirstVisiblePosition();
        int top = c.getTop();

        int headerHeight = 0;
        if (firstVisiblePosition >= 1) {
            headerHeight = mTopHideView.getHeight();
        }

        return -top + firstVisiblePosition * c.getHeight() + headerHeight;
    }

} 

// Note : Don't forget to call **setActionBarRefernce method ** of custom listener

Answer 5

This library helps for animation https://github.com/ksoichiro/Android-ObservableScrollView

Answer 6

There is official documentation on how to achieve this effect: https://developer.android.com/training/basics/actionbar/overlaying.html

Edit: There is an open source library ObservableScrollView with a lot of open source demos with different ActionBar effects, including the ones you mentioned. It's a great resource: https://github.com/ksoichiro/Android-ObservableScrollView.