Keyboard padding detection heuristic to distringuish when to include bottom inset. (#6288)

GaryQian · web-flow · commit 74625aed323d · 2018-09-24T11:38:13.000-07:00
Use a screen height ratio to determine if the keyboard is onscreen or not. This is used because Android does not provide a deterministic API to detect this.

We remove the padding when the keyboard is closed and the inset is due to the hidden navigation bar, otherwise, we apply the full keyboard inset.
diff --git a/shell/platform/android/io/flutter/view/FlutterView.java b/shell/platform/android/io/flutter/view/FlutterView.java
@@ -575,6 +575,29 @@ else if (rotation == Surface.ROTATION_0 || rotation == Surface.ROTATION_180) {
         return ZeroSides.NONE;
     }
 
+    // TODO(garyq): Use clean ways to detect keyboard instead of heuristics if possible
+    // TODO(garyq): The keyboard detection may interact strangely with
+    //   https://github.com/flutter/flutter/issues/22061
+
+    // Uses inset heights and screen heights as a heuristic to determine if the insets should
+    // be padded. When the on-screen keyboard is detected, we want to include the full inset
+    // but when the inset is just the hidden nav bar, we want to provide a zero inset so the space
+    // can be used.
+    int calculateBottomKeyboardInset(WindowInsets insets) {
+        int screenHeight = getRootView().getHeight();
+        // Magic number due to this being a heuristic. This should be replaced, but we have not
+        // found a clean way to do it yet (Sept. 2018)
+        final double keyboardHeightRatioHeuristic = 0.18;
+        if (insets.getSystemWindowInsetBottom() < screenHeight * keyboardHeightRatioHeuristic) {
+            // Is not a keyboard, so return zero as inset.
+            return 0;
+        }
+        else {
+            // Is a keyboard, so return the full inset.
+            return insets.getSystemWindowInsetBottom();
+        }
+    }
+
     // This callback is not present in API < 20, which means lower API devices will see
     // the wider than expected padding when the status and navigation bars are hidden.
     @Override
@@ -602,8 +625,10 @@ public final WindowInsets onApplyWindowInsets(WindowInsets insets) {
         // Bottom system inset (keyboard) should adjust scrollable bottom edge (inset).
         mMetrics.physicalViewInsetTop = 0;
         mMetrics.physicalViewInsetRight = 0;
-        // TODO(garyq): Detect and distinguish between bottom nav padding and keyboard padding.
-        mMetrics.physicalViewInsetBottom = insets.getSystemWindowInsetBottom();
+        // We perform hidden navbar and keyboard handling if the navbar is set to hidden. Otherwise,
+        // the navbar padding should always be provided.
+        mMetrics.physicalViewInsetBottom =
+            navigationBarHidden ? calculateBottomKeyboardInset(insets) : insets.getSystemWindowInsetBottom();
         mMetrics.physicalViewInsetLeft = 0;
         updateViewportMetrics();
         return super.onApplyWindowInsets(insets);
