Android：如何以编程方式设置浮动操作按钮的重力？

Question

I want to move the position of Floating action button programmatically at a certain place in some fragment because sometimes the floating action is covering the important contents of that fragment. I got the reference of floating action button in the activity and stored it in a static variable.I am trying to change its gravity in the onResume method of the fragment. As you can see in the image that fab is covering y-axis so I want to move it to the END. Image for the reference .

The code in the onResume method of the fragment(not working):

override fun onResume() {
    super.onResume()
    val params : CoordinatorLayout.LayoutParams = BaseActivity.fab!!.layoutParams as CoordinatorLayout.LayoutParams
    params.anchorGravity = GravityCompat.END
    BaseActivity.fab!!.layoutParams = params
}

XML file of main activity

<?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:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.mandar.hackerthon_app.Activities.BaseActivity"
    tools:showIn="@layout/app_bar_base">

    <FrameLayout
        android:id="@+id/frameBaseFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></FrameLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_margin="20dp"
        android:scaleType="center"
        android:elevation="10dp"
        app:backgroundTint="@color/common_google_signin_btn_text_dark_default"
        app:srcCompat="@mipmap/ic_connection_on_round" />

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

Answer 1

In your XML file, add the app:layout_anchor property for FloatingActionButton , as layout_anchorGravity is only taken into account if you specify an anchor view.

In your case, this anchor may be @id/frameBaseFragment . Note that if you want to move FloatingActionButton to the bottom-end of its CoordinatorLayout parent, you may instead change the value of layoutGravity .

Also, it is strongly discouraged to store references to Views in static variables as it prevents the associated Activity from being garbage-collected, causing huge memory leaks. This might also be the cause of your problem.

Answer 2

fab does not have a gravity property but other layouts do. So an approach I found was to wrap the fab I have in another layout:

// ... FloatingActionButton fab defined somewhere ...

val fabHolder = LinearLayout(this.context)  // layout type irrelevant
fabHolder.layoutParams = LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT)
fabHolder.gravity = Gravity.END or Gravity.BOTTOM  // bottom-right
fabHolder.addView(fab)

relView.addView(fabHolder)

This replaces the following line of code:

relView.addView(fab)