Android fitsSystemWindows not working when replacing fragments

Question

I have SingleFramgnetActivity whose purpose is only to hold and replace fragments inside it.

layout looks like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    tools:context=".SingleFragmentActivity"
    >

    <include layout="@layout/toolbar"/>

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

I'm replacing the Fragments inside the FrameLayout. When I set the fitsSystemWindows to true on the Fragment layout, it is not responding. Actually it is working only when Activity is created, but once I replace the Fragment inside the FrameLayout, the fitsSystemWindows parameter is ignored and the layout is below the status bar and navigation bar.

I found some solution with custom FrameLayout which is using deprecated methods, but for some reason it is not working for me (same result as with normal FrameLayout) and I also do not like the idea to use deprecated methods.

Answer 1

Your FrameLayout is not aware of window inset sizes, because it's parent - LinearLayout hasn't dispatched it any. As a workaround, you can subclass LinearLayout and pass insets to children on your own:

@TargetApi(Build.VERSION_CODES.KITKAT_WATCH)
@Override
public WindowInsets onApplyWindowInsets(WindowInsets insets) {
    int childCount = getChildCount();
    for (int index = 0; index < childCount; index++)
        getChildAt(index).dispatchApplyWindowInsets(insets); // let children know about WindowInsets

    return insets;
}

You can have a look to my this answer, which will explain detailed how this works, and also how to use ViewCompat.setOnApplyWindowInsetsListener API.

Answer 2

You could also build a custom WindowInsetsFrameLayout and use a OnHierarchyChangedListener to request applying the insets again:

public WindowInsetsFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

    // Look for replaced fragments and apply the insets again.
    setOnHierarchyChangeListener(new OnHierarchyChangeListener() {
        @Override
        public void onChildViewAdded(View parent, View child) {
            requestApplyInsets();
        }

        @Override
        public void onChildViewRemoved(View parent, View child) {

        }
    });
}

Check out this detailed answer: https://stackoverflow.com/a/47349880/3979479

Answer 3

I think the problem revolves around onApplyWindowInsets getting called before the fragment view hierarchy gets attached. An effective solution is to get the following override on a view somewhere in the view hierarchy of the fragment.

  @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        // force window insets to get re-applied if we're being attached by a fragment.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
            requestApplyInsets();
        } else {
            //noinspection deprecation
            requestFitSystemWindows();
        }
    }

A complete solution (if you don't have to use CoordinatorLayout) follows. Make sure fitSystemWindows=true does not appear ANYWHERE in views higher in the heirarchy. Maybe not anywhere else. I suspect (but am not sure) that consumeSystemWindowInsets eats the insets for views that are further on in the layout order of the view tree.

package com.twoplay.xcontrols;

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Rect;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.WindowInsets;
import android.widget.FrameLayout;

public class FitSystemWindowsLayout extends FrameLayout {
    private boolean mFit = true;

    public FitSystemWindowsLayout(final Context context) {
        super(context);
        init();
    }

    public FitSystemWindowsLayout(final Context context, final AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public FitSystemWindowsLayout(final Context context, final AttributeSet attrs, final int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        setFitsSystemWindows(true);
    }

    public boolean isFit() {
        return mFit;
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
            requestApplyInsets();
        } else {
            //noinspection deprecation
            requestFitSystemWindows();
        }

    }

    public void setFit(final boolean fit) {
        if (mFit == fit) {
            return;
        }

        mFit = fit;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
            requestApplyInsets();
        } else {
            //noinspection deprecation
            requestFitSystemWindows();
        }
    }

    @SuppressWarnings("deprecation")
    @Override
    protected boolean fitSystemWindows(final Rect insets) {
        if (mFit) {
            setPadding(
                    insets.left,
                    insets.top,
                    insets.right,
                    insets.bottom
            );
            return true;
        } else {
            setPadding(0, 0, 0, 0);
            return false;
        }
    }

    @TargetApi(Build.VERSION_CODES.KITKAT_WATCH)
    @Override
    public WindowInsets onApplyWindowInsets(final WindowInsets insets) {
        if (mFit) {
            setPadding(
                    insets.getSystemWindowInsetLeft(),
                    insets.getSystemWindowInsetTop(),
                    insets.getSystemWindowInsetRight(),
                    insets.getSystemWindowInsetBottom()
            );
            return insets.consumeSystemWindowInsets();
        } else {
            setPadding(0, 0, 0, 0);
            return insets;
        }
    }
}

Suspicion, not fact: that only one view in the entire hierarchy gets a chance to eat the window insets, UNLESS you have CoordinatorLayout in the hierarchy, which allows more than one direct child to have FitSystemWindow=true. If you do have a CoordinatorLayout, your mileage may vary.

This entire feature in Android seems to be an unholy mess.