Initial checkin of AOSP Messaging app.

b/23110861 Change-Id: I9aa980d7569247d6b2ca78f5dcb4502e1eaadb8a
2015-08-12 08:58:28 -07:00
parent 8b3e2b9c1b
commit 461a34b466
1645 changed files with 186271 additions and 0 deletions
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+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.messaging.ui;
+
+import android.os.Parcelable;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * The base pager view holder implementation that handles basic view creation/destruction logic,
+ * as well as logic to save/restore instance state that's persisted not only for activity
+ * reconstruction (e.g. during a configuration change), but also cases where the individual
+ * page view gets destroyed and recreated.
+ *
+ * To opt into saving/restoring instance state behavior for a particular page view, let the
+ * PageView implement PersistentInstanceState to save and restore instance states to/from a
+ * Parcelable.
+ */
+public abstract class BasePagerViewHolder implements PagerViewHolder {
+    protected View mView;
+    protected Parcelable mSavedState;
+
+    /**
+     * This is called when the entire view pager is being torn down (due to configuration change
+     * for example) that will be restored later.
+     */
+    @Override
+    public Parcelable saveState() {
+        savePendingState();
+        return mSavedState;
+    }
+
+    /**
+     * This is called when the view pager is being restored.
+     */
+    @Override
+    public void restoreState(final Parcelable restoredState) {
+        if (restoredState != null) {
+            mSavedState = restoredState;
+            // If the view is already there, let it restore the state. Otherwise, it will be
+            // restored the next time the view gets created.
+            restorePendingState();
+        }
+    }
+
+    @Override
+    public void resetState() {
+        mSavedState = null;
+        if (mView != null && (mView instanceof PersistentInstanceState)) {
+            ((PersistentInstanceState) mView).resetState();
+        }
+    }
+
+    /**
+     * This is called when the view itself is being torn down. This may happen when the user
+     * has flipped to another page in the view pager, so we want to save the current state if
+     * possible.
+     */
+    @Override
+    public View destroyView() {
+        savePendingState();
+        final View retView = mView;
+        mView = null;
+        return retView;
+    }
+
+    @Override
+    public View getView(ViewGroup container) {
+        if (mView == null) {
+            mView = createView(container);
+            // When initially created, check if the view has any saved state. If so restore it.
+            restorePendingState();
+        }
+        return mView;
+    }
+
+    private void savePendingState() {
+        if (mView != null && (mView instanceof PersistentInstanceState)) {
+            mSavedState = ((PersistentInstanceState) mView).saveState();
+        }
+    }
+
+    private void restorePendingState() {
+        if (mView != null && (mView instanceof PersistentInstanceState) && (mSavedState != null)) {
+            ((PersistentInstanceState) mView).restoreState(mSavedState);
+        }
+    }
+
+    /**
+     * Create and initialize a new page view.
+     */
+    protected abstract View createView(ViewGroup container);
+}