Develop Reference

Control RecyclerView inflated views from outside the adapter: keep selection state

Generally
I want to control the ViewHolder inflated Views of my RecyclerView from outside of the ViewHolder and the RecyclerView classes. In other words, I want to have control of these views from other methods/classes.
My case (en example)
In my specific case, I made a photo gallery activity which allows the user to perform selection and deselection of each inflated view, notifying which items are selected by highlighting them.
For now, the user is able to do that by clicking each generated object / View; then, actions on specific child of RecyclerView / adapter are possible thanks to "setOnClickListener" and "setOnLongClickListener" methods, which perform the corresponding actions in methods inside the ViewHolder class.
But when activity is restarted (i.e. for device rotation) the selection goes lost and the user should perform the selection again (i.e. for deleting photos).
Assuming that positions of the selected photos are kept (for example via bundle, or via an array) is possible to restore selection (i.e. highlighting the corresponding item / views) on the adapter views after that the activity is re-started? If yes, how?
Some code
The code below contains the Recyclerview class and the AdapterView class, which both are child of an activity Class.
private class ImageGalleryAdapter extends RecyclerView.Adapter<ImageGalleryAdapter.MyViewHolder> {
private ArrayList<PhotoObject.PhotoElement> photoAL;
private Context mContext;
public ImageGalleryAdapter(Context context, ArrayList<PhotoObject.PhotoElement> photosToPreviewInGallery) {
mContext = context;
photoAL = photosToPreviewInGallery;
}
#Override
public ImageGalleryAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
Context context = parent.getContext();
LayoutInflater inflater = LayoutInflater.from(context);
// Inflate the layout
View itemView = inflater.inflate(R.layout.item_photo, parent, false);
ImageGalleryAdapter.MyViewHolder viewHolder = new ImageGalleryAdapter.MyViewHolder(itemView);
// Retrieving the itemView
return viewHolder;
}
#Override
public void onBindViewHolder(ImageGalleryAdapter.MyViewHolder holder, int position) {
PhotoObject.PhotoElement previewPhotoInGallery = photoAL.get(position);
ImageView imageView = holder.mPhotoImageView;
GlideApp.with(mContext)
.load(previewPhotoInGallery.getUrl())
.placeholder(R.drawable.ic_cloud_off_red)
.into(imageView);
}
//The method which gives back the number of items to load as photo.
#Override
public int getItemCount() {
return (photoAL.size());
}
// The class that assigns a view holder for each Image and checkbox in the RecyclerView.
public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
public ImageView mPhotoImageView;
public CheckBox mPhotoCheckBox;
public MyViewHolder(View item_view) {
super(item_view);
mPhotoImageView = (ImageView) item_view.findViewById(R.id.item_photo_iv);
mPhotoCheckBox = (CheckBox) item_view.findViewById(R.id.item_photo_checkbox);
item_view.setOnClickListener(this);
item_view.setOnLongClickListener(this);
// Retrieving the item_view
}
// The method for managing the click on an image.
#Override
public void onClick(View view) {
itemSelection(view);
}
// Manages the selection of the items.
private void itemSelection(View item) {
// Retrieving the item
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION) {
if (!item.isSelected()) {
// Add clicked item to the selected ones
MultiPhotoShootingActivity.manageSelection(true, position);
// Visually highlighting the ImageView
item.setSelected(true);
mPhotoCheckBox.setChecked(true);
mPhotoCheckBox.setVisibility(View.VISIBLE);
} else {
// Remove clicked item from the selected ones
MultiPhotoShootingActivity.manageSelection(false, position);
// Removing the visual highlights on the ImageView
item.setSelected(false);
mPhotoCheckBox.setChecked(false);
mPhotoCheckBox.setVisibility(View.INVISIBLE);
}
}
}
// The method for managing the long click on an image.
#Override
public boolean onLongClick(View view) {
int position = getAdapterPosition();
if(position != RecyclerView.NO_POSITION) {
Intent intent = new Intent(mContext, PhotoDetail.class);
intent.putExtra("KEY4URL", activityPhotoObject.getPath(position));
startActivity(intent);
}
// return true to indicate that the click was handled (if you return false onClick will be triggered too)
return true;
}
}
}
Thank you for your time.

You shouldn't "control" views from outside the adapter. Instead, Override onSaveState and onRestoreState in your activity. Make same methods in your adapter with passing the bundle to the adapter in order to save state. save an integer array of positions that were selected into the bundle(that you passed into an adapter). In corresponding way, you can get the array of selected positions from the bundle of On restore state.
activity:
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState){
adapter.onRestoreInstanceState(savedInstanceState);
}
in your adapter:
public void onRestoreInstanceState(Bundle state){
selectedItemsArray = state.getIntArray("my_array_key")
}

#Alessandro
You can handle the Runtime changes by yourself.
In your manifest, you can define the changes that your activity will handle by itself and it will not be restarted.
android:configChanges="orientation|keyboardHidden"
After that, you'll have to handle the Configuration changes that you declared in your manifest using this method in your activity:
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Checks the orientation of the screen
if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
// Do your thing
}
}

SOLVED
Find out that for solving the problem I had to accomplish two little tasks:
saving and restoring the selected item selection state (for example via an array, as helpfully suggested by #Inkognito);
retrieving the views for applying the selection, based on the position inside the RecyclerView.
So, I had to modify some code.
Before proceeding, I would like to point out that the Activity class has a sub-class, which is the Adapter class (named ImageGalleryAdapter); the Adapter subclass, in turn, has its own subclass, which is the ViewHolder class (named MyViewHolder).
So: Activity class -> Adapter class -> ViewHolder class
Code modified in the parent class (the activity class, in which the RecyclerView is)
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
adapter.onSaveInstanceState(outState);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
adapter.onRestoreInstanceState(savedInstanceState);
}
In the onSaveInstanceState and onRestoreInstanceState methods, I added the references for saving and restoring instance states of the "adapter" sub-class.
Code added in the adapter class (which is inside the RecyclerView class)
private boolean [] selectedItemsArray;
private void onSaveInstanceState(Bundle outState) {
outState.putBooleanArray("my_array_key" , selectedItemsArray = mpsaPO.getItemsSelected());
}
private void onRestoreInstanceState(Bundle state) {
if (state != null) {
selectedItemsArray = state.getBooleanArray("my_array_key");
}
}
The selectedItemsArray is a boolean array in which the information of which elements of the RecyclerView are selected (true = selected; false = not selected) is contained.
Then, adding this element in the saved instance and retrieved via the activity class, makes the app able to know which are the views selected after that the activity is re-created.
Code added inside the onBindViewHolder method, which is inside the adapter class
if (selectedItemsArray != null) {
if (selectedItemsArray[position]) {
holder.itemView.setSelected(true);
holder.mPhotoCheckBox.setChecked(true);
holder.mPhotoCheckBox.setVisibility(View.VISIBLE);
}
}
With this last part of code, we are applying the selection to the corresponding views based on which items/views were selected before that the activity was saved.
The holer object contains the itemView and mPhotoCheckBox objectsm on which we can perform the selection.

How get value from adapter class to activity Class

I am having adapter class, In that, I need to pass invoiceId to an Activity Class. I have seen some example like pass-through interface, but I lost track on following the code procedure.
Here Is My Adapter Class extends BaseAdapter
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
companyName = ct.getSharedPreferences("prefs", 0);
Log.d("test", "" + deliveryListBeans.size());
LayoutInflater inflater = (LayoutInflater) ct.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflater.inflate(R.layout.list_vew_for_delivery_order, null);
TextView invoice = (TextView) v.findViewById(R.id.invoice);
final TextView delivery = (TextView) v.findViewById(R.id.do_delivery);
final DeliveryListBean dlb = deliveryListBeans.get(position);
invoice.setText(dlb.getInvoiceNo());
}
delivery.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ct.startActivity(new Intent(ct, EmployeesListForPopUp.class));
DeliveryOrdersListAdapter deliveryOrdersListAdapter=new DeliveryOrdersListAdapter(EmployeesListForPopUp.this);
}
});
}
Here is My Activity Class
public class EmployeesListForPopUp extends Activity {
private List<EmployeeIdNameBean> employeeIdNameBeans = new ArrayList<EmployeeIdNameBean>();
ListView listView;
SharedPreferences companyName;
EmployeePopUpAdapter employeePopUpAdapter;
private ImageView img1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_employees_list_for_pop_up);
I need to get invoiceId from Adapter Class. How?

You need to pass context of the activity in adapters constructor.
Then set activity.invoiceid value in clickevents of adapter.

One simple way is that you write a method in MainActivity
public void setInvoiceId(int invoiceId) {
// do what you want with invoiceId
}
and pass the instance of your activity to adapter
DeliveryOrdersListAdapter adapter = new DeliveryOrdersListAdapter(EmployeesListForPopUp.this);
and get it in your adapter and keep it
EmployeesListForPopUp myActivity;
public MyAdapter(EmployeesListForPopUp activity) {
myActivity = activity;
}
and where you need to pass invoiceId just call the method of main activity
myActivity.setInvoiceId(invoiceId);

General way of implementing it:
In the adapter class, where you set text to invoice TextView, you also can add a tag to it. Put attention - despite every item in the list is build from the same prototype, the tag (as well as text) will be uniq. The best way is to use "position" as value of the tag: invoice.setText(dlb.getInvoiceNo());
invoice.setTag(Integer.valueOf(position).toString());
You need to make your items in the list clickable (this is out of the scope of this question). So, when you click on some item - you can retrieve any data it has, and specifically tag - getTag();.
Then you send Intent to other activity, providing the tag as extra message. So that activity will "know" which item in the array list it is related to (i.e. tag == position, right?). And continue from there.
I implemented simple project that illustrates it. This project is simple demo and illustration of working with ArrayList adapter,
displaying the item in the ListView, clicking on some item and display relevant data in separated activity. Please download it and try (min API 21). Basic description is available in README file.
The project is here on the GitHub:
(corrected path)
https://github.com/everall77/ArrayListSimpleExmpl

Restore Android GridView after screen orientation change (without reloading it)

I'm new to Android (this is my first application) and I made a GridView in an Activity which I'd like it to be responsive according to screen position (portrait / landscape). Of course I made some custom layout values of GridView rows width for portrait as well as for landscape, and it works perfectly.
Except that, on every screen orientation change, the GridView is reloading again. And that's not good for user experience. I only like the GridView (and definitely its rows) to adjust to new screen width without doing all the onCreate() instructions (retrieving GridView's data from internet, assigning retrieved data in a HashMap object, setting the GridView's Adapter, then display the GridView's rows).
I went through many forum threads and some Google documentation that talk about restoring simple values, but never found an answer for restoring a GridView without having it to reload again.
I read about onSaveInstanceState() and onRestoreInstanceState(), but I didn't know how to use them in my case (GridView case).
Could any one provide a simple code sample for this? Or at least some headlines to follow?
Here's some of what I tried in my code, in the Activity class :
private Parcelable mListInstanceState;
private Parcelable mAdapterInstanceState;
private GridView gridView = null;
private MyAdapter myAdapter = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gridView = (GridView) findViewById(R.id.gridview);
// Check whether we're recreating a previously destroyed instance
if(savedInstanceState != null) {
// Restore value of members from saved state
mListInstanceState = savedInstanceState.getParcelable("gridview");
mAdapterInstanceState = savedInstanceState.getParcelable("adapter");
}
else {
// Retrieve data from internet, fill HashMap object,
// set Adapter and display GridView only for the first time the activity is created
attemptToDisplayGirdViewItems();
}
}
#Override
protected void onSaveInstanceState(Bundle state) {
// Save activity state
super.onSaveInstanceState(state);
state.putParcelable("gridview", gridView.onSaveInstanceState());
// state.putParcelable("adapter", myAdapter);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
// Retrieve and restore activity state
// Restore state members from saved instance
mListInstanceState = savedInstanceState.getParcelable("gridview");
mAdapterInstanceState = savedInstanceState.getParcelable("adapter");
super.onRestoreInstanceState(savedInstanceState);
}

You don't need to save the views. If they have ID, they'll be saved automatically (such as scroll position of a GridView). What you need to save is the adapter's data set.
Your adapter presumably holds a list of items. Unless these items are primitives or String or implement Serializable, they need to implement Parcelable for this to work.
See here how to do that: How can I make my custom objects Parcelable?
Your adapter needs a getItems method which returns the data set - an ArrayList of your parcelable items. It also needs to have a setItems(...) method or a constructor taking a list of items as parameter.
Then your activity will look like this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gridView = (GridView) findViewById(R.id.gridview);
myAdapter = new MyAdapter(); // Create empty adapter.
if(savedInstanceState != null) {
ArrayList<MyItem> items = savedInstanceState.getParcelableArrayList("myAdapter");
myAdapter.setItems(items); // Load saved data if any.
}
gridView.setAdapter(myAdapter);
}
#Override
protected void onSaveInstanceState(Bundle state) {
super.onSaveInstanceState(state);
state.putParcelableArrayList("myAdapter", myAdapter.getItems());
}

Android programming: I cant get data to reload into arrayadapter

I am still stuck with this issue, can anyone help. It seems that my problem is that I cant update the data list. I have tried every solution that I've searched for on google etc.. but half the time i'm not even sure that I'm doing the correct thing.
I've used the onResume() to call notifyDataSetChanged, it didn't work. I've tried putting a refresh method into the adapter which i then called in OnResume(). Again it didn't work. Some people suggest clearing the adpater (adapter.clear();) in onResume and then using the addAll() function to relist the data but nothing works.
There has to be a simple solution to this. I have literally been stuck on this for 2 days now. very frustrated.
Here's my Fragment code again...
enter code here
public class SavedAppFragment extends ListFragment {
private static final String TAG = "AppClicked"; //DEBUGGER
private ArrayList<App> mSavedApps;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Populate the ArrayList
mSavedApps = SavedAppData.get(getActivity()).getApps();
AppAdapter adapter = new AppAdapter(mSavedApps);
setListAdapter(adapter);
}
//LIST ITEM CLICKED: /*Control what happens when list item is clicked: I.E. Load up a quiz while putting an EXTRA key containg the package name of the App to be launhced should the user get the question correct */ #Override public void onListItemClick(ListView l, View v, int position,long id) { //Return the crime for the list item that was clicked App c = ((AppAdapter) getListAdapter()).getItem(position); Log.d(TAG, "was clicked");
//Start the Activity that will list the detail of the app
Intent i = new Intent(getActivity(), Quiz_Activity.class);
String name = c.getPackage();
i.putExtra("packagename", name);
startActivity(i);
}
private class AppAdapter extends ArrayAdapter {
private ArrayList<App> mSavedApps;
public AppAdapter(ArrayList<App> apps) {
super(getActivity(), 0, apps);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
//If we weren't given a view, inflate one
if (null == convertView) {
convertView = getActivity().getLayoutInflater().inflate(R.layout.list_item_app, null);
//((AppAdapter) getListAdapter()).notifyDataSetChanged();
}
((AppAdapter) getListAdapter()).notifyDataSetChanged();
//Configure the view for this crime
App c = getItem(position);
TextView nameTextView = (TextView) convertView.findViewById(R.id.app_name);
nameTextView.setText(c.getName());
// nameTextView.setText(applicationInfo.loadLabel(packageManager));
TextView packageTextView = (TextView) convertView.findViewById(R.id.app_package);
packageTextView.setText(c.getPackage());
CheckBox appCheckBox = (CheckBox) convertView.findViewById(R.id.app_checked);
appCheckBox.setChecked(c.isChecked());
//Return the view object to the ListView
return convertView;
}
}
}
THANKS!!!

When you return to Activity B, the previous Activity B hasn't been destroyed. Thus, it skips the onCreate. Move all of the stuff you want to make sure happens every time into the onResume. I think you want to make your Adapter a class variable (I'll call it mAdapter) in onCreate, and add code that will get data from the list directly. If you need to do something, put a "refresh" function in the adapter. I'm assuming you have a custom Adapter, because I've never heard of AppAdapter. If you don't, then extend AppAdapter and add that functionality. Thus, your onCreate should look like this:
mAdapter = new AppAdapter(mSavedApps);
setListAdapter(mAdapter);
Your onRefresh could update the data contained in the adapter by some new update function, like so:
mAdapter.update(SavedAppData.get(getActivity()).getApps());

Retaining list in list fragment on orientation change

I have an app using fragments, all of which are contained in a single activity. The activity starts with a fragment containing a menu of buttons, all of which cause various listfragments to replace the original button/menu fragment.
My problem is that upon an orientation change, if the activity is displaying one of the listviews, it goes away and the button menu returns. I understand why this is happening... the activity is destroyed and re-created, but not how to work around it and maintain the list view/current fragment through the orientation change.
I've found setRetainInstance and the example of use here, but I can't figure out how to apply it to my situation with the button menu or the possibility that the fragment I want to retain could be one of several different ones.
Below is code simplified to show the main activity and one of the listfragments.
Any pointers in what to add where to make it so that the list fragment will be retained would be greatly appreciated.
Activity
public class Main extends FragmentActivity {
private MainMenuFragment menu;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
menu = new MainMenuFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.pane, menu).commit();
}
}
ListFragment
public class ItemListFragment extends ListFragment {
private TextView header;
private TextView empty;
private Button add;
public static Cursor itemCursor;
private GroceryDB mDbHelper;
public static long mRowId;
public static CheckCursorAdapter lists;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.common_list, container, false);
header = (TextView) v.findViewById(R.id.header);
empty = (TextView) v.findViewById(android.R.id.empty);
header.setText(R.string.header_item);
empty.setText(R.string.empty_items);
return v;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mRowId=0;
mDbHelper = new GroceryDB(getActivity());
mDbHelper.open();
itemCursor = mDbHelper.fetchAllItems();
getActivity().startManagingCursor(itemCursor);
String[] from = new String[] { GroceryDB.ITEM_NAME };
int[] to = new int[] { R.id.ListItem };
lists = new CheckCursorAdapter(getActivity(),
R.layout.listlayout_itemlist, itemCursor, from, to);
setListAdapter(lists);
}
}

how to work around it and maintain the list view/current fragment through the orientation change
You are blindly replacing the fragment every time onCreate() is called. Instead, only add/replace the fragment if savedInstanceState() is null. If it is not null, you are coming back from a configuration change, and your existing fragments will be recreated (or, if they were retained, they are already there).
setRetainInstance(true) means that the fragment itself will be retained across configuration changes, instead of being destroyed/recreated like the activity is. However, it will still be called with onCreateView(). In your code, that means that your data members of ItemListFragment would stick around, but you would still need to call setListAdapter() even if you do not requery the database.

I know that this has been resolved a long time ago, but for the sake of people searching for a solution who have as much issues as I've (repeatedly) had with retaining lists during an orientation change I would like to add that you could also use a custom class which holds the list of data for your listadapter.
This way it keeps the data when recreating the activity (and listfragment) and you can just test to see if it has any data in your oncreate. If the list == null or the list.size < 0 you proceed as usual and get the data whatever way you normally get it. Otherwise you just set your listadapter with the data it already has.
To me this is a lot easier, and seeing as Eclipse automatically creates a similar DummyContent class for your data when creating an android master/detail flow project it basically only requires a change of the oncreate of your listfragment.