Support "display": "fullscreen" for sites added to the home screen.

chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.webapps;
 
 import android.content.Intent;
+import android.os.Build;
 import android.util.Pair;
 import android.view.View;
+import android.view.View.OnSystemUiVisibilityChangeListener;
 import android.view.ViewGroup;
 
 import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.TabState;
 import org.chromium.chrome.browser.compositor.layouts.LayoutManagerDocument;
 import org.chromium.chrome.browser.tab.EmptyTabObserver;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabDelegateFactory;
@@ skipping 19 matching lines @@
  * Activity would be webapps and streaming media activities - anything where user interaction with
  * the regular browser's UI is either unnecessary or undesirable.
  * Subclasses can override {@link #createUI()} if they need something more exotic.
  */
 @SuppressFBWarnings("URF_UNREAD_FIELD")
 public abstract class FullScreenActivity extends ChromeActivity {
     protected static final String BUNDLE_TAB_ID = "tabId";
     protected static final String BUNDLE_TAB_URL = "tabUrl";
     private static final String TAG = "FullScreenActivity";
 
+    private static final int ENTER_IMMERSIVE_MODE_DELAY_MILLIS = 300;
+    private static final int RESTORE_IMMERSIVE_MODE_DELAY_MILLIS = 3000;
+    private static final int IMMERSIVE_MODE_UI_FLAGS =
+            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
+                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
+                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
+                | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
+                | View.SYSTEM_UI_FLAG_LOW_PROFILE
+                | View.SYSTEM_UI_FLAG_IMMERSIVE;
+
+    private boolean mEnableImmersive;
+    private boolean mEnteredImmersive;
+
     private Tab mTab;
 
     private WebContents mWebContents;
     @SuppressWarnings("unused") // Reference needed to prevent GC.
     private WebContentsObserver mWebContentsObserver;
 
     @Override
     protected void onNewIntent(Intent intent) {
         super.onNewIntent(intent);
         setIntent(intent);
@@ skipping 113 matching lines @@
             public void didCommitProvisionalLoadForFrame(
                     long frameId, boolean isMainFrame, String url, int transitionType) {
                 if (!isMainFrame) return;
                 // Notify the renderer to permanently hide the top controls since they do
                 // not apply to fullscreen content views.
                 mTab.updateBrowserControlsState(mTab.getBrowserControlsStateConstraints(), true);
             }
         };
     }
 
+    @Override
+    public void onWindowFocusChanged(boolean hasFocus) {
+        super.onWindowFocusChanged(hasFocus);
+
+        if (hasFocus && mEnableImmersive) {
+            enterImmersiveMode(getWindow().getDecorView());
+        }
+    }
+
+    /**
+     * Ensure the given {@link View} is in fullscreen immersion if this device supports.
+     */
+    protected void enterImmersiveMode(final View decor) {
+        if (!supportsImmersiveMode()) {
+            return;
+        }
+        mEnableImmersive = true;
+
+        // Register a SystemUiVisibilityChangeListener to restore immersive mode.

[dominickn, 2017/01/16 22:49:01]

Can these comments be a little more descriptive? Something like:

// When we enter immersive mode for the first time, register a
SystemUiVisibilityChangeListener that restores immersive mode. This is necessary
because user actions like focusing a keyboard will break out of immersive.

+        if (!mEnteredImmersive) {
+            decor.setOnSystemUiVisibilityChangeListener(new OnSystemUiVisibilityChangeListener() {
+                @Override
+                public void onSystemUiVisibilityChange(int newFlags) {
+                    delaySetImmersive(decor, newFlags, RESTORE_IMMERSIVE_MODE_DELAY_MILLIS);
+                }
+            });
+        }
+        // Set Immersive mode on demand.

[dominickn, 2017/01/16 22:49:01]

Nit: add a newline above this comment, and explain why you have a short delay to
enter

[Leo, 2017/01/18 05:09:40]

Actually I just follow the sample codes created by Google and copy the 300 ms as
a friendly delay.
IMO, the main purpose is just to be asynchronous. Setting a short delay is not
required but could tolerate some annoying system faults. 

https://android.googlesource.com/platform/development/+/e7a6ab4/samples/devby...

[dominickn, 2017/01/18 05:56:17]

Ah, I see, that makes sense.

+        delaySetImmersive(decor, decor.getSystemUiVisibility(), ENTER_IMMERSIVE_MODE_DELAY_MILLIS);
+        mEnteredImmersive = true;
+    }
+
+    private void delaySetImmersive(final View decor, final int flags, int delayInMills) {
+        mHandler.postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                int desiredFlags = flags | IMMERSIVE_MODE_UI_FLAGS;
+                if (flags != desiredFlags) {
+                    decor.setSystemUiVisibility(desiredFlags);
+                }
+            }
+        }, delayInMills);
+    }
+
     /**
      * @return {@link TabDelegateFactory} to be used while creating the associated {@link Tab}.
      */
     protected TabDelegateFactory createTabDelegateFactory() {
         return new FullScreenDelegateFactory();
     }
 
     /**
      * @return {@link File} pointing at a directory specific for this class.
      */
     protected File getActivityDirectory() {
         return null;
     }
 
     @Override
     protected boolean handleBackPressed() {
         if (mTab == null) return false;
         if (mTab.canGoBack()) {
             mTab.goBack();
             return true;
         }
         return false;
     }
 
     @Override
     public void onCheckForUpdate(boolean updateAvailable) {
     }
+
+    /**
+     ** @return true if this device supports immersive mode functionality.
+     **/
+    public static boolean supportsImmersiveMode() {
+        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
+    }
 }