Prevent CollapsingToolbarLayout collapse if not needed

Question

Using:

compile 'com.android.support:design:23.0.0'
compile 'com.android.support:appcompat-v7:23.0.0'
compile 'com.android.support:cardview-v7:23.0.0'
compile 'com.android.support:recyclerview-v7:23.0.0'

With the project Cheesesquare updated.

Into the detail of cheese, I remove 2 cards (to have only one). Is there a way to prevent the collapsing of the toolbar that show a blank space?

Solution 1

To implement such behaviour in Cheesesquare example just modify android:layout_height param of the NestedScrollView to wrap_content. It will prevent scrolling by content if it is small enough to fit on the screen.

And to prevent scrolling by CollapsingToolbarLayout you should programmatically set layout_scrollFlags parameter to the AppBarLayout.LayoutParams.SCROLL_FLAG_SNAP value.

Here described how you can do this.

Solution 2

You can use below code for this:

   public static void stopScroll() {
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) collapsing_toolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(0);
    collapsing_toolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appbar.getLayoutParams();
    appBarLayoutParams.setBehavior(null);
    appbar.setLayoutParams(appBarLayoutParams);
}

public static void startScroll() {
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) collapsing_toolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
    collapsing_toolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appbar.getLayoutParams();
    appBarLayoutParams.setBehavior(new AppBarLayout.Behavior());
    appbar.setLayoutParams(appBarLayoutParams);
}

Solution 3

In xml I have used property

app:layout_scrollFlags="snap" in <android.support.design.widget.CollapsingToolbarLayout

and following in the activity

 toolbar = (Toolbar) findViewById(R.id.toolbar);
 setSupportActionBar(toolbar);
 toolbar.setTitle(null);
 toolbar.setCollapsible(false);

It is working now.

Solution 4

A data-binding solution inspired by @Vishal's answer

    <com.google.android.material.appbar.AppBarLayout>
        <com.google.android.material.appbar.CollapsingToolbarLayout
            app:enableCollapsingScroll="@{listItems.size > 0}"
            ... />
    </com.google.android.material.appbar.AppBarLayout>

    @BindingAdapter("app:enableCollapsingScroll")
    fun setCollapsingToolbarLayoutScrollEnabled(collapsingToolbarLayout: CollapsingToolbarLayout, enabled: Boolean?) {
        val lp = collapsingToolbarLayout.layoutParams as AppBarLayout.LayoutParams
        if (enabled.orFalse()) {
            lp.scrollFlags = AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL or AppBarLayout.LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED
        } else {
            lp.scrollFlags = AppBarLayout.LayoutParams.SCROLL_FLAG_SNAP
        }
        collapsingToolbarLayout.layoutParams = lp
    }

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