以编程方式设置 app:layout_behavior

Question

I have a coordinator layout with a recyclerview which I would like to add programmatically. The reason why it's added programatically is because different fragments which inflate the coordinator layout, may use different types of recyclerviews.

Typically for a recyclerview, in order to set this behaviour I would add it in the xml:

app:layout_behavior="@string/appbar_scrolling_view_behavior"

That works fine. However, I'm at a complete loss as to how to add this behavior when I create the recyclerviews programmatically and then add them to the framelayout:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:id="@+id/coordLayout"
    android:layout_height="match_parent" android:fitsSystemWindows="true"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout android:id="@+id/app_bar"
        android:fitsSystemWindows="true" android:layout_height="@dimen/app_bar_height"
        android:layout_width="match_parent" android:theme="@style/AppTheme.AppBarOverlay">

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

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_height="?attr/actionBarSize"
                android:layout_width="match_parent"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

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

    </android.support.design.widget.AppBarLayout>
    <FrameLayout
        android:id="@+id/frameLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </FrameLayout>

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

Answer 1

Explanation

Behavior is a parameter of the CoordinatorLayout.LayoutParams . You can set the behavior on an instance of CoordinatorLayout.LayoutParams with setBehavior method.

To get a proper Behavior object that represents the same thing as @string/appbar_scrolling_view_behavior you should create an instance of AppBarLayout.ScrollingViewBehavior .

---

Example

( this is a cleaned up version of my previous edits to the original answer )

First you will have to get an instance of a child View of your CoordinatorLayout . Let me get this clear: it is NOT the CoordinatorLayout itself. childView is CoordinatorLayout's child.

//e.g. like this:
val childView: View = findViewById(R.id.child_view)

Assuming the childView is already attached to the CoordinatorLayout (so it already has LayoutParams ), you can do:

val params: CoordinatorLayout.LayoutParams = yourView.layoutParams as CoordinatorLayout.LayoutParams
params.behavior = AppBarLayout.ScrollingViewBehavior()
yourView.requestLayout()

Answer 2

To enable and disable layout_behavior programatically with kotlin use this code :

fun enableLayoutBehaviour() {
    val param: CoordinatorLayout.LayoutParams = swipeRefreshView.layoutParams as CoordinatorLayout.LayoutParams
    param.behavior = AppBarLayout.ScrollingViewBehavior()
}

fun disableLayoutBehaviour() {
    val param: CoordinatorLayout.LayoutParams = swipeRefreshView.layoutParams as CoordinatorLayout.LayoutParams
    param.behavior = null
}

Note: replace swipeRefreshView with your view

Answer 3

Accepted answer is correct but the provided code is not compilable. So here is a complete example

CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) 
view.getLayoutParams();

params.setBehavior(new AppBarLayout.ScrollingViewBehavior(view.getContext(), null));

2nd param is AttributeSet and it is fine to have it as null although it is not marked as Nullable in support lib.