Programmatically collapse or expand CollapsingToolbarLayout

Simple question, but I can't find an answer. How can I collapse or expand the CollapsingToolbarLayout programmatically?

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Using Support Library v23, you can call appBarLayout.setExpanded(true/false).

Further reading: AppBarLayout.setExpanded(boolean)

I use this code for collapsing toolbar. Still cannot find a way to expand it.

public void collapseToolbar(){
    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appbarLayout.getLayoutParams();
    behavior = (AppBarLayout.Behavior) params.getBehavior();
    if(behavior!=null) {
        behavior.onNestedFling(rootLayout, appbarLayout, null, 0, 10000, true);
    }
}

Edit 1: The same function with negative velocityY but the toolbar is not expanded 100% and false for last param should work

public void expandToolbar(){
    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appbarLayout.getLayoutParams();
    behavior = (AppBarLayout.Behavior) params.getBehavior();
    if(behavior!=null) {
        behavior.onNestedFling(rootLayout, appbarLayout, null, 0, -10000, false);
    }
}

Edit 2: This code do the trick for me

public void expandToolbar(){
    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appbarLayout.getLayoutParams();
    behavior = (AppBarLayout.Behavior) params.getBehavior();
    if(behavior!=null) {
        behavior.setTopAndBottomOffset(0);
        behavior.onNestedPreScroll(rootLayout, appbarLayout, null, 0, 1, new int[2]);
    }
}

• setTopAndBottomOffset do expand the toolbar
• onNestedPreScroll do show the content inside expanded toolbar

Will try to implement Behavior by myself.

You can define how much it expands or collapses with your custom animator. Just use the setTopAndBottomOffset(int).

Here is an example:

CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appBar.getLayoutParams();
final AppBarLayout.Behavior behavior = (AppBarLayout.Behavior) params.getBehavior();
if (behavior != null) {
    ValueAnimator valueAnimator = ValueAnimator.ofInt();
    valueAnimator.setInterpolator(new DecelerateInterpolator());
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            behavior.setTopAndBottomOffset((Integer) animation.getAnimatedValue());
            appBar.requestLayout();
        }
    });
    valueAnimator.setIntValues(0, -900);
    valueAnimator.setDuration(400);
    valueAnimator.start();
}

I've written a small extension to AppBarLayout. It allows for expanding and collapsing of the CollapsibleToolbarLayout both with and without animation. It seems to be doing it quite right.

Feel free to try it out.

Just use it instead of your AppBarLayout, and you can call methods responsible for expanding or collapsing of the CollapsingToolbarLayout.

It's working exactly as expected in my project, but you might need to tweak the fling/scroll values in the perform... methods (especially in performExpandingWithAnimation()) to fit perfectly with your CollapsibleToolbarLayout.

Use mAppBarLayout.setExpanded(true) to expand Toolbar and use mAppBarLayout.setExpanded(false) to collapse Toolbar.

If you want to change CollapsingToolbarLayout height programmatically then just use mAppBarLayout.setLayoutParams(params);

Expand:

CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) mAppBarLayout.getLayoutParams();
params.height = 3*200; // HEIGHT

mAppBarLayout.setLayoutParams(params);
mAppBarLayout.setExpanded(true);

Collapse:

CoordinatorLayout.LayoutParams params =(CoordinatorLayout.LayoutParams) mAppBarLayout.getLayoutParams();
params.height = 3*80; // HEIGHT

mAppBarLayout.setLayoutParams(params);
mAppBarLayout.setExpanded(false);

for the ones who wants to work with onNestedPreScroll and get error like me. i get NullPointerException in onCreate with out this line

    CoordinatorLayout coordinator =(CoordinatorLayout)findViewById(R.id.tab_maincontent);
    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    //below line
    params.setBehavior(new AppBarLayout.Behavior() {});

and doesn't work properly with this. but i work around this problem with

in onCreate :

        scrollToolbarOnDelay();

and...

    public void scrollToolbarOnDelay() {
            final Handler handler = new Handler();
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.tab_appbar);
                    CoordinatorLayout coordinator = (CoordinatorLayout) findViewById(R.id.tab_maincontent);
                    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
                    AppBarLayout.Behavior behavior = (AppBarLayout.Behavior) params.getBehavior();
         if(behavior!=null)
                    behavior.onNestedPreScroll(coordinator, appBarLayout, null, 0, 100, new int[]{0, 0});
         else
            scrollToolbarOnDelay()
                }
            }, 100);
    
    
        }

Try this...

Expand

appBarLayout.setExpanded(true, true);

To recall

appBarLayout.setExpanded(false, true);

To expand/collapse AppBarLayout programmatically:

fun expandAppBarLayout(expand: Boolean, isAnimationEnabled: Boolean){
    appBarLayout.setExpanded(expand, isAnimationEnabled);
}

This may help to expand or collapse :

appBarLayout.setActivated(true);
appBarLayout.setExpanded(true, true);

i have using this

 private fun collapseAppbar() {
        scrollView.postDelayed(Runnable {
            scrollView?.smoothScrollTo(50, 50)
        }, 400)
    }