Android 4.4 — Translucent status/navigation bars — fitsSystemWindows/clipToPadding don't work through fragment transactions

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余生分开走
余生分开走 2021-01-30 11:30

When using the translucent status and navigation bars from the new Android 4.4 KitKat APIs, setting fitsSystemWindows=\"true\" and clipToPadding=\"false\"

8条回答
  •  [愿得一人]
    2021-01-30 11:47

    I struggled with the same problem yesterday. After thinking a lot, I found an elegant solution to this problem.

    First, I saw the method requestFitSystemWindows() on ViewParent and I tried to call it in the fragment's onActivityCreated() (after the Fragment is attached to the view hierarchy) but sadly it had no effect. I would like to see a concrete example of how to use that method.

    Then I found a neat workaround: I created a custom FitsSystemWindowsFrameLayout that I use as a fragment container in my layouts, as a drop-in replacement for a classic FrameLayout. What it does is memorizing the window insets when fitSystemWindows() is called by the system, then it propagates the call again to its child layout (the fragment layout) as soon as the fragment is added/attached.

    Here's the full code:

    public class FitsSystemWindowsFrameLayout extends FrameLayout {
    
        private Rect windowInsets = new Rect();
        private Rect tempInsets = new Rect();
    
        public FitsSystemWindowsFrameLayout(Context context) {
            super(context);
        }
    
        public FitsSystemWindowsFrameLayout(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    
        public FitsSystemWindowsFrameLayout(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
        }
    
        @Override
        protected boolean fitSystemWindows(Rect insets) {
            windowInsets.set(insets);
            super.fitSystemWindows(insets);
            return false;
        }
    
        @Override
        public void addView(View child, int index, ViewGroup.LayoutParams params) {
            super.addView(child, index, params);
            tempInsets.set(windowInsets);
            super.fitSystemWindows(tempInsets);
        }
    }
    

    I think this is much simpler and more robust than hacks that try to determine the UI elements sizes by accessing hidden system properties which may vary over time and then manually apply padding to the elements.

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