Observer Support for DistilledPagePrefs

components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java

Index: components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java
diff --git a/components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java b/components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java
index 3ec91baca8c91ad490fec48100bb72e9609e96e9..d69d4fb8adaaa486d85fe3872f551ad39c4dfd74 100644
--- a/components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java
+++ b/components/dom_distiller/android/java/src/org/chromium/components/dom_distiller/core/DistilledPagePrefs.java
@@ -4,7 +4,12 @@
 
 package org.chromium.components.dom_distiller.core;
 
+import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
+import org.chromium.base.NativeCall;
+
+import java.util.HashMap;
+import java.util.Map;
 
 /**
  * Wrapper for the dom_distiller::DistilledPagePrefs.
@@ -13,25 +18,85 @@ import org.chromium.base.JNINamespace;
 public final class DistilledPagePrefs {
 
     private final long mDistilledPagePrefsAndroid;
+    private Map<Observer, DistilledPagePrefsObserverWrapper> mObserverMap;
+
+    /**
+     * Observer interface for observing DistilledPagePrefs changes.
+     */
+    public interface Observer {
+        void onChangeTheme(Theme theme);
+    }
+
+    /**
+     * Wrapper for dom_distiller::android::DistilledPagePrefsObserverAndroid.
+     */
+    private static class DistilledPagePrefsObserverWrapper {
+        private final Observer mDistilledPagePrefsObserver;
+        private final long mNativeDistilledPagePrefsObserverAndroidPtr;
+
+        public DistilledPagePrefsObserverWrapper(Observer observer) {
+            mNativeDistilledPagePrefsObserverAndroidPtr = nativeInitObserverAndroid();
+            mDistilledPagePrefsObserver = observer;
+        }
+
+        @CalledByNative("DistilledPagePrefsObserverWrapper")
+        private void onChangeTheme(int theme) {
+            mDistilledPagePrefsObserver.onChangeTheme(Theme.getThemeForValue(theme));
+        }
+
+        public void destroy() {
+            nativeDestroyObserverAndroid(mNativeDistilledPagePrefsObserverAndroidPtr);
+        }
+
+        public long getNativePtr() {
+            return mNativeDistilledPagePrefsObserverAndroidPtr;
+        }
+
+        @NativeCall("DistilledPagePrefsObserverWrapper")
+        private native long nativeInitObserverAndroid();
+
+        @NativeCall("DistilledPagePrefsObserverWrapper")
+        private native void nativeDestroyObserverAndroid(
+                long nativeDistilledPagePrefsObserverAndroid);
+    }
 
     DistilledPagePrefs(long distilledPagePrefsPtr) {
         mDistilledPagePrefsAndroid = nativeInit(distilledPagePrefsPtr);
+        mObserverMap = new HashMap<Observer, DistilledPagePrefsObserverWrapper>();
+    }
+
+    public void addObserver(Observer obs) {
+        DistilledPagePrefsObserverWrapper wrappedObserver =
+                new DistilledPagePrefsObserverWrapper(obs);
+        nativeAddObserver(mDistilledPagePrefsAndroid, wrappedObserver.getNativePtr());
+        mObserverMap.put(obs, wrappedObserver);
+    }
+
+    public void removeObserver(Observer obs) {
+        DistilledPagePrefsObserverWrapper wrappedObserver = mObserverMap.remove(obs);
+        if (wrappedObserver != null) {
+            nativeRemoveObserver(mDistilledPagePrefsAndroid, wrappedObserver.getNativePtr());
+            wrappedObserver.destroy();
+        }
     }
 
-    // TODO(sunangel): Add observer support from this Java class to native
-    // counterpart so UI can be updated across tabs.
     public void setTheme(Theme theme) {
         nativeSetTheme(mDistilledPagePrefsAndroid, theme.asNativeEnum());
     }
 
     public Theme getTheme() {
-        return Theme.getThemeForValue(
-            nativeGetTheme(mDistilledPagePrefsAndroid));
+        return Theme.getThemeForValue(nativeGetTheme(mDistilledPagePrefsAndroid));
     }
 
     private native long nativeInit(long distilledPagePrefPtr);
-    private native void nativeSetTheme(long nativeDistilledPagePrefsAndroid,
-        int theme);
-    private native int nativeGetTheme(
-        long nativeDistilledPagePrefsAndroid);
+
+    private native void nativeSetTheme(long nativeDistilledPagePrefsAndroid, int theme);
+
+    private native int nativeGetTheme(long nativeDistilledPagePrefsAndroid);
+
+    private native void nativeAddObserver(long nativeDistilledPagePrefsAndroid,
+            long nativeObserverPtr);
+
+    private native void nativeRemoveObserver(long nativeDistilledPagePrefsAndroid,
+            long nativeObserverPtr);
 }