107 lines
3.5 KiB
Java
107 lines
3.5 KiB
Java
/*
|
|
* 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);
|
|
}
|