Reduce flickers of Injection

The injection dynamic data was loaded in the background and then post to
main thread to update UI. However, it usually updates after
Fragement.onResume(), which causes the flicker.

To make it more smooth, DashboardFragment to wait for the dynamic data
observers to update UI for a short period, which eliminates the flicker
in most cases.

Also skip the repeated tiles refresh called by onCategoriesChanged in
onResume after all preferences refreshed.

Test: robotest, visual
Bug: 229177114
Change-Id: I04650af9692703f1fc1e6e5ad2090f051b1eeb81

src/com/android/settings/dashboard/DynamicDataObserver.java

@@ -20,13 +20,24 @@ import android.net.Uri;
 import android.os.Handler;
 import android.os.Looper;
 
+import com.android.settingslib.utils.ThreadUtils;
+
+import java.util.concurrent.CountDownLatch;
+
 /**
  * Observer for updating injected dynamic data.
  */
 public abstract class DynamicDataObserver extends ContentObserver {
 
+    private Runnable mUpdateRunnable;
+    private CountDownLatch mCountDownLatch;
+    private boolean mUpdateDelegated;
+
     protected DynamicDataObserver() {
         super(new Handler(Looper.getMainLooper()));
+        mCountDownLatch = new CountDownLatch(1);
+        // Load data for the first time
+        onDataChanged();
     }
 
     /** Returns the uri of the callback. */
@@ -35,8 +46,30 @@ public abstract class DynamicDataObserver extends ContentObserver {
     /** Called when data changes. */
     public abstract void onDataChanged();
 
+    /** Calls the runnable to update UI */
+    public synchronized void updateUi() {
+        mUpdateDelegated = true;
+        if (mUpdateRunnable != null) {
+            mUpdateRunnable.run();
+        }
+    }
+
+    /** Returns the count-down latch */
+    public CountDownLatch getCountDownLatch() {
+        return mCountDownLatch;
+    }
+
     @Override
     public void onChange(boolean selfChange) {
         onDataChanged();
     }
+
+    protected synchronized void post(Runnable runnable) {
+        if (mUpdateDelegated) {
+            ThreadUtils.postOnMainThread(runnable);
+        } else {
+            mUpdateRunnable = runnable;
+            mCountDownLatch.countDown();
+        }
+    }
 }