Fullscreen media preview on tap.

res/drawable/image_preview_shade.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+
+    <gradient
+        android:angle="90"
+        android:startColor="@color/media_preview_bar_background"
+        android:centerColor="@color/media_preview_bar_shade_center"
+        android:endColor="@android:color/transparent"/>
+
+</shape>

res/layout/media_preview_activity.xml

@@ -19,11 +19,12 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_gravity="bottom"
-        android:orientation="vertical"
+        android:animateLayoutChanges="true"
-        android:background="@drawable/image_shade"
+        android:background="@drawable/image_preview_shade"
         android:gravity="bottom"
+        android:orientation="vertical"
         android:visibility="gone"
-        android:animateLayoutChanges="true">
+        tools:visibility="visible">
 
         <org.thoughtcrime.securesms.components.MaxHeightScrollView
             android:id="@+id/media_preview_caption_container"
@@ -64,4 +65,19 @@
 
     </LinearLayout>
 
+    <com.google.android.material.appbar.AppBarLayout
+        android:id="@+id/toolbar_layout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="@color/media_preview_bar_background"
+        app:elevation="0dp">
+
+        <androidx.appcompat.widget.Toolbar
+            android:id="@+id/toolbar"
+            android:layout_width="match_parent"
+            android:layout_height="?attr/actionBarSize"
+            android:background="@android:color/transparent" />
+
+    </com.google.android.material.appbar.AppBarLayout>
+
 </FrameLayout>

res/values-v21/themes.xml

@@ -10,4 +10,8 @@
         <item name="android:colorControlActivated">@color/signal_primary_dark</item>
     </style>
 
+    <style name="TextSecure.MediaPreview" parent="@style/TextSecure.BaseMediaPreview">
+        <item name="android:navigationBarColor">@color/media_preview_bar_background</item>
+    </style>
+
 </resources>

res/values/colors.xml

@@ -70,4 +70,7 @@
 
     <color name="avatar_background">@color/transparent_black_90</color>
 
+    <color name="media_preview_bar_background">#90010101</color>
+    <color name="media_preview_bar_shade_center">#88000000</color>
+
 </resources>

res/values/themes.xml

@@ -26,6 +26,15 @@
     </style>
 
     <style name="TextSecure.DarkNoActionBar" parent="@style/TextSecure.BaseDarkNoActionBar">
+
+    </style>
+
+    <style name="TextSecure.BaseMediaPreview" parent="@style/TextSecure.BaseDarkNoActionBar">
+        <item name="colorPrimaryDark">@color/media_preview_bar_background</item>
+        <item name="android:textColorSecondary">@color/white</item>
+    </style>
+
+    <style name="TextSecure.MediaPreview" parent="@style/TextSecure.BaseMediaPreview">
         <!-- leave empty to allow overriding -->
     </style>
 

src/org/thoughtcrime/securesms/MediaPreviewActivity.java

@@ -29,6 +29,7 @@ import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.Window;
 import android.view.WindowManager;
 import android.widget.TextView;
 import android.widget.Toast;
@@ -37,6 +38,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AlertDialog;
 import androidx.core.util.Pair;
+import androidx.core.view.ViewCompat;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentStatePagerAdapter;
@@ -109,20 +111,22 @@ public final class MediaPreviewActivity extends PassphraseRequiredActionBarActiv
 
   private int restartItem = -1;
 
-
   @SuppressWarnings("ConstantConditions")
   @Override
   protected void onCreate(Bundle bundle, boolean ready) {
-    this.setTheme(R.style.TextSecure_DarkTheme);
+    this.setTheme(R.style.TextSecure_MediaPreview);
+    setContentView(R.layout.media_preview_activity);
+
+    setSupportActionBar(findViewById(R.id.toolbar));
 
     viewModel = ViewModelProviders.of(this).get(MediaPreviewViewModel.class);
 
-    getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_FULLSCREEN);
     getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                          WindowManager.LayoutParams.FLAG_FULLSCREEN);
 
+    showSystemUI();
+
     getSupportActionBar().setDisplayHomeAsUpEnabled(true);
-    setContentView(R.layout.media_preview_activity);
 
     initializeViews();
     initializeResources();
@@ -208,6 +212,14 @@ public final class MediaPreviewActivity extends PassphraseRequiredActionBarActiv
     caption                   = findViewById(R.id.media_preview_caption);
     captionContainer          = findViewById(R.id.media_preview_caption_container);
     playbackControlsContainer = findViewById(R.id.media_preview_playback_controls_container);
+
+    View toolbarLayout = findViewById(R.id.toolbar_layout);
+
+    anchorMarginsToBottomInsets(detailsContainer);
+
+    anchorMarginsToTopInsets(toolbarLayout);
+
+    showAndHideWithSystemUI(getWindow(), detailsContainer, toolbarLayout);
   }
 
   private void initializeResources() {
@@ -439,11 +451,36 @@ public final class MediaPreviewActivity extends PassphraseRequiredActionBarActiv
 
   @Override
   public boolean singleTapOnMedia() {
-    detailsContainer.setVisibility(detailsContainer.getVisibility() == View.VISIBLE ? View.GONE : View.VISIBLE);
+    toggleUiVisibility();
-
     return true;
   }
 
+  private void toggleUiVisibility() {
+    int systemUiVisibility = getWindow().getDecorView().getSystemUiVisibility();
+    if ((systemUiVisibility & View.SYSTEM_UI_FLAG_FULLSCREEN) != 0) {
+      showSystemUI();
+    } else {
+      hideSystemUI();
+    }
+  }
+
+  private void hideSystemUI() {
+    getWindow().getDecorView().setSystemUiVisibility(
+        View.SYSTEM_UI_FLAG_IMMERSIVE              |
+        View.SYSTEM_UI_FLAG_LAYOUT_STABLE          |
+        View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
+        View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN      |
+        View.SYSTEM_UI_FLAG_HIDE_NAVIGATION        |
+        View.SYSTEM_UI_FLAG_FULLSCREEN              );
+  }
+
+  private void showSystemUI() {
+    getWindow().getDecorView().setSystemUiVisibility(
+        View.SYSTEM_UI_FLAG_LAYOUT_STABLE          |
+        View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
+        View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN       );
+  }
+
   private class ViewPagerListener extends ExtendedOnPageChangedListener {
 
     @Override
@@ -534,6 +571,48 @@ public final class MediaPreviewActivity extends PassphraseRequiredActionBarActiv
     }
   }
 
+  private static void anchorMarginsToBottomInsets(@NonNull View viewToAnchor) {
+    ViewCompat.setOnApplyWindowInsetsListener(viewToAnchor, (view, insets) -> {
+      ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) view.getLayoutParams();
+
+      layoutParams.setMargins(insets.getSystemWindowInsetLeft(),
+                              layoutParams.topMargin,
+                              insets.getSystemWindowInsetRight(),
+                              insets.getSystemWindowInsetBottom());
+
+      view.setLayoutParams(layoutParams);
+
+      return insets;
+    });
+  }
+
+  private static void anchorMarginsToTopInsets(@NonNull View viewToAnchor) {
+    ViewCompat.setOnApplyWindowInsetsListener(viewToAnchor, (view, insets) -> {
+      ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) view.getLayoutParams();
+
+      layoutParams.setMargins(insets.getSystemWindowInsetLeft(),
+                              insets.getSystemWindowInsetTop(),
+                              insets.getSystemWindowInsetRight(),
+                              layoutParams.bottomMargin);
+
+      view.setLayoutParams(layoutParams);
+
+      return insets;
+    });
+  }
+
+  private static void showAndHideWithSystemUI(@NonNull Window window, @NonNull View... views) {
+    window.getDecorView().setOnSystemUiVisibilityChangeListener(visibility -> {
+      boolean hide = (visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) != 0;
+
+      for (View view : views) {
+        view.animate()
+            .alpha(hide ? 0 : 1)
+            .start();
+      }
+    });
+  }
+
   private static class CursorPagerAdapter extends FragmentStatePagerAdapter implements MediaItemAdapter {
 
     @SuppressLint("UseSparseArrays")