Make Clipboard.java a singleton pattern.

ui/android/java/src/org/chromium/ui/base/Clipboard.java

 // Copyright 2013 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.ui.base;
 
 import android.content.ClipData;
 import android.content.ClipboardManager;
 import android.content.Context;
 
+import org.chromium.base.ContextUtils;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.ui.R;
 import org.chromium.ui.widget.Toast;
 
 /**
- * Simple proxy that provides C++ code with an access pathway to the Android
- * clipboard.
+ * Simple proxy that provides C++ code with an access pathway to the Android clipboard.
  */
 @JNINamespace("ui")
 public class Clipboard {
+    private static Clipboard sInstance;
+
     // Necessary for coercing clipboard contents to text if they require
     // access to network resources, etceteras (e.g., URI in clipboard)
     private final Context mContext;
 
     private final ClipboardManager mClipboardManager;
 
     /**
-     * Use the factory constructor instead.
-     *
-     * @param context for accessing the clipboard
+     * Get the singleton Clipboard instance (creating it if needed).
      */
-    public Clipboard(final Context context) {
-        mContext = context;
-        mClipboardManager = (ClipboardManager)
-                context.getSystemService(Context.CLIPBOARD_SERVICE);
+    @CalledByNative
+    public static Clipboard getInstance() {
+        if (sInstance == null) {
+            sInstance = new Clipboard();
+        }
+        return sInstance;
+    }
+
+    private Clipboard() {
+        mContext = ContextUtils.getApplicationContext();
+        mClipboardManager =
+                (ClipboardManager) ContextUtils.getApplicationContext().getSystemService(
+                        Context.CLIPBOARD_SERVICE);
     }
 
     /**
-     * Returns a new Clipboard object bound to the specified context.
-     *
-     * @param context for accessing the clipboard
-     * @return the new object
-     */
-    @CalledByNative
-    private static Clipboard create(final Context context) {
-        return new Clipboard(context);
-    }
-
-    /**
      * Emulates the behavior of the now-deprecated
      * {@link android.text.ClipboardManager#getText()} by invoking
      * {@link android.content.ClipData.Item#coerceToText(Context)} on the first
      * item in the clipboard (if any) and returning the result as a string.
      * <p>
      * This is quite different than simply calling {@link Object#toString()} on
      * the clip; consumers of this API should familiarize themselves with the
      * process described in
      * {@link android.content.ClipData.Item#coerceToText(Context)} before using
      * this method.
@@ skipping 73 matching lines @@
     private void setPrimaryClipNoException(ClipData clip) {
         try {
             mClipboardManager.setPrimaryClip(clip);
         } catch (Exception ex) {
             // Ignore any exceptions here as certain devices have bugs and will fail.
             String text = mContext.getString(R.string.copy_to_clipboard_failure_message);
             Toast.makeText(mContext, text, Toast.LENGTH_SHORT).show();
         }
     }
 }