android - Toolbar expands on swipe down

Question

In my application I have a collapsing Toolbar. If I start a specific Fragment I want to collapse the Toolbar so it behaves like a "normal" one and that the user can not expend it by himself. Here is my layout which I use for my Toolbar:

<android.support.design.widget.AppBarLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/appBarLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <android.support.design.widget.CollapsingToolbarLayout
        android:id="@+id/collapsing_toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:contentScrim="?attr/colorPrimary"
        app:expandedTitleMarginEnd="64dp"
        app:expandedTitleMarginStart="48dp"
        app:titleEnabled="false"
        app:layout_scrollFlags="scroll|exitUntilCollapsed">

        <ImageView
            android:src="@drawable/drawer_background"
            app:layout_scrollFlags="scroll|enterAlways|enterAlwaysCollapsed"
            android:layout_width="match_parent"
            android:layout_height="172dp"
            android:scaleType="centerCrop"
            app:layout_collapseMode="parallax"
            android:minHeight="100dp" />

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolBar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_collapseMode="pin"
            app:layout_scrollFlags="scroll|enterAlways" />

    </android.support.design.widget.CollapsingToolbarLayout>

</android.support.design.widget.AppBarLayout>

I also can collapse the layout from code like so:

appBarLayout.setExpanded(false, false);

final AppBarLayout.LayoutParams params = (AppBarLayout.LayoutParams) collapsingToolbarLayout.getLayoutParams();
params.setScrollFlags(0);
collapsingToolbarLayout.setLayoutParams(params);

But this does not help. If the user swipes down from the Toolbar it will expand.

Do you have any ideas why?

Answer 1

The core problem is that there is no CollapsingToolbarLayout.lock(); method up until now (v23.2.1 of support design). Hopefully, this feature will be included in a future version. Until then, I'm suggesting the following workaround:

You can collapse and lock your toolbar with:

appbar.setExpanded(false,false);
CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
lp.height = (int) getResources().getDimension(R.dimen.toolbar_height);

and unlock it with:

 CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
 lp.height = (int) getResources().getDimension(R.dimen.nav_header_height);

However, with the above code a problem occurs:

when forcefully collapsing CoordinatorLayout the title of our Toolbar is gone and CollapsingToolbarLayout.setTitle(CharSequence title); no longer works. To fix that we add a TextView in our Toolbar and manipulate its visibility accordingly. (we want it "gone" in a fragment that has its toolbar 'unlocked' and "visible" in a fragment that has its toolbar 'locked'.

We have to set TextView's android:textAppearance to be the same with CollapsingToolbarLayout's app:collapsedTitleTextAppearance to be consistent and avoid disrupting the user with different toolbar text sizes and colors.

In summary, with an interface like this:

public interface ToolbarManipulation {
    void collapseToolbar();
    void expandToolbar();
    void setTitle(String s);
}

implemantations like these:

@Override
    public void collapseToolbar(){
        appbar.setExpanded(false,false);
        CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
        lp.height = (int) getResources().getDimension(R.dimen.toolbar_height);
        toolbarCollapsedTitle.setVisibility(View.VISIBLE);
    }

    @Override
    public void expandToolbar() {
        CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
        lp.height = (int) getResources().getDimension(R.dimen.nav_header_height);
        toolbarCollapsedTitle.setVisibility(View.GONE);
    }

    @Override
    public void setTitle(String s) {
        collapsingToolbarLayout.setTitle(s);
        toolbarCollapsedTitle.setText(s);
        collapsingToolbarLayout.invalidate();
        toolbarCollapsedTitle.invalidate();
    }

and main xml like this:

....
  <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:collapsedTitleTextAppearance="@style/CollapsedAppBar"

            >
                <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    android:layout_width="match_parent"
                    android:layout_height="?attr/actionBarSize"
                    android:background="?attr/colorPrimary"
                    app:layout_collapseMode="pin"
                    app:popupTheme="@style/AppTheme.PopupOverlay"
                    >
                    <TextView
                        android:layout_width="match_parent"
                        android:layout_height="?attr/actionBarSize"
                        android:visibility="gone"
                        android:layout_gravity="center_vertical|start"
                        android:gravity="center_vertical|start"
                        android:id="@+id/toolbar_collapsed_title"
                        android:textAppearance="@style/CollapsedAppBar"
                        />
                </android.support.v7.widget.Toolbar>
        </android.support.design.widget.CollapsingToolbarLayout>
......

you can lock and unlock your Toolbar as you like. Your fragments should call these functions in their onResume();

I've uploaded an example implementation here.

Note: This is just a workaround and obviously not the cleanest solution. We're waiting for a newer version of com.android.support to resolve this.