Fix 'No Apps' UI issues of ManageApplications

Fixes below UI issues

- "No Apps" may not show in fragments of profile tab.

  Fix it by using ConstraintLayout to specify alignments
  of each view and removing extra padding.

-- "No Apps" may flicker by moving position.

  The flicker is from unnecessary visibility changes.
  This change integrates empty view visibility
  control in LoadingViewController to simplify code
  and avoid unnecessary visibility changes.

Bug: 189390795
Bug: 183398721
Test: atest com.android.settings.deviceinfo
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.deviceinfo
      Manual visual, observe UI
        Settings -> Storage -> Games
        Settings -> Notifications -> App Settings
	Settings > Apps > Special app access > Media management apps
Change-Id: I634209c6f8466e2adae703226902190bbdf470b9

src/com/android/settings/widget/LoadingViewController.java

@@ -22,34 +22,66 @@ import android.view.View;
 import android.view.animation.Animation;
 import android.view.animation.AnimationUtils;
 
+import androidx.annotation.Nullable;
+
 /**
- * A helper class that manages show/hide loading spinner.
+ * A helper class that manages show/hide loading spinner, content view and empty view (optional).
  */
 public class LoadingViewController {
 
     private static final long DELAY_SHOW_LOADING_CONTAINER_THRESHOLD_MS = 100L;
 
-    public final Handler mFgHandler;
-    public final View mLoadingView;
-    public final View mContentView;
+    private final Handler mFgHandler;
+    private final View mLoadingView;
+    private final View mContentView;
+    private final View mEmptyView;
 
     public LoadingViewController(View loadingView, View contentView) {
+        this(loadingView, contentView, null /* emptyView*/);
+    }
+
+    public LoadingViewController(View loadingView, View contentView, @Nullable View emptyView) {
         mLoadingView = loadingView;
         mContentView = contentView;
+        mEmptyView = emptyView;
         mFgHandler = new Handler(Looper.getMainLooper());
     }
 
     private Runnable mShowLoadingContainerRunnable = new Runnable() {
         public void run() {
-            handleLoadingContainer(false /* done */, false /* animate */);
+            showLoadingView();
         }
     };
 
+    /**
+     *  Shows content view and hides loading view & empty view.
+     */
     public void showContent(boolean animate) {
         // Cancel any pending task to show the loading animation and show the list of
         // apps directly.
         mFgHandler.removeCallbacks(mShowLoadingContainerRunnable);
-        handleLoadingContainer(true /* show */, animate);
+        handleLoadingContainer(true /* showContent */, false /* showEmpty*/, animate);
+    }
+
+    /**
+     *  Shows empty view and hides loading view & content view.
+     */
+    public void showEmpty(boolean animate) {
+        if (mEmptyView == null) {
+            return;
+        }
+
+        // Cancel any pending task to show the loading animation and show the list of
+        // apps directly.
+        mFgHandler.removeCallbacks(mShowLoadingContainerRunnable);
+        handleLoadingContainer(false /* showContent */, true /* showEmpty */, animate);
+    }
+
+    /**
+     *  Shows loading view and hides content view & empty view.
+     */
+    public void showLoadingView() {
+        handleLoadingContainer(false /* showContent */, false /* showEmpty */, false /* animate */);
     }
 
     public void showLoadingViewDelayed() {
@@ -57,8 +89,9 @@ public class LoadingViewController {
                 mShowLoadingContainerRunnable, DELAY_SHOW_LOADING_CONTAINER_THRESHOLD_MS);
     }
 
-    public void handleLoadingContainer(boolean done, boolean animate) {
-        handleLoadingContainer(mLoadingView, mContentView, done, animate);
+    private void handleLoadingContainer(boolean showContent, boolean showEmpty, boolean animate) {
+        handleLoadingContainer(mLoadingView, mContentView, mEmptyView,
+                showContent, showEmpty, animate);
     }
 
     /**
@@ -75,6 +108,25 @@ public class LoadingViewController {
         setViewShown(content, done, animate);
     }
 
+    /**
+     * Show/hide loading view and content view and empty view.
+     *
+     * @param loading The loading spinner view
+     * @param content The content view
+     * @param empty The empty view shows no item summary to users.
+     * @param showContent    If true, content is set visible and loading is set invisible.
+     * @param showEmpty    If true, empty is set visible and loading is set invisible.
+     * @param animate Whether or not content/loading views should animate in/out.
+     */
+    public static void handleLoadingContainer(View loading, View content, View empty,
+            boolean showContent, boolean showEmpty, boolean animate) {
+        if (empty != null) {
+            setViewShown(empty, showEmpty, animate);
+        }
+        setViewShown(content, showContent, animate);
+        setViewShown(loading, !showContent && !showEmpty, animate);
+    }
+
     private static void setViewShown(final View view, boolean shown, boolean animate) {
         if (animate) {
             Animation animation = AnimationUtils.loadAnimation(view.getContext(),