I'm using the Google Leanback widgets in an Android TV application. It utilizes a RowsFragment with ListRows in it.
What I'm trying to determine is if there is any way to programmatically scroll to a particular object within one of the rows. I've dug into the docs for the Leanback widgets but cannot find what I'm looking for.
I had a similar necessity: I needed to set the initial selected item in a ListRow.
I ended up subclassing the ListRowPresenter like this:
import android.support.v17.leanback.widget.ListRowPresenter;
import android.support.v17.leanback.widget.RowPresenter;
public class CustomPresenter extends ListRowPresenter {
private int mInitialSelectedPosition;
public CustomPresenter(int position) {
this.mInitialSelectedPosition = position;
}
#Override
protected void onBindRowViewHolder(RowPresenter.ViewHolder holder, Object item) {
super.onBindRowViewHolder(holder, item);
ViewHolder vh = (ListRowPresenter.ViewHolder) holder;
vh.getGridView().setSelectedPosition(mInitialSelectedPosition);
}
}
Hopefully this will help you.
In the latest version of Leanback (think v23.3.0+), you can now specify not only the row position but also perform optional tasks on the row. In your case, the task would be programmatic selection like so:
BrowseFragment.setSelectedPosition(0, true, new ListRowPresenter.SelectItemViewHolderTask(2));
No need to implement custom list row presenters or anything
I've done it when I needed to implement "Return to the first item in a Row by pressing Back".
I was calling this method from Activity's onBackPressed().
If this method returns false we call Activity.super.onBackPressed().
If true - we don't.
public boolean onBackPressed(){
boolean consumeBack;
int selectedRowPosition = getRowsFragment().getSelectedPosition();
ListRowPresenter.ViewHolder selectedRow = (ListRowPresenter.ViewHolder) getRowsFragment().getRowViewHolder(selectedRowPosition);
int selectedItemPosition = selectedRow.getSelectedPosition();
if(selectedItemPosition == 0){
consumeBack = false;
} else {
consumeBack = true;
getRowsFragment().setSelectedPosition(selectedRowPosition, true, new ListRowPresenter.SelectItemViewHolderTask(0));
}
return consumeBack;
}
Instead of "0" you can set any position you need.
This answer is suggesting the usage of the latest androidx.leanback library.
In your BrowseSupportFragment create a class variable of type HeadersSupportFragment. After creating your ArrayObjectAdapter and using it by setAdapter(), call the getHeadersSupportFragment(). Then call getSelectedPosition() to get the current selected position and store it in Preferences. Later, use setSelectedPosition() to set the previous position.
Here is an example:
private HeadersSupportFragment hsp;
private ArrayObjectAdapter mRowsAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mRowsAdapter = new ArrayObjectAdapter(new ListRowPresenter());
setAdapter(mRowsAdapter);
hsp = getHeadersSupportFragment();
int lastPosition = getSharedPreferences(CONTEXT).getInt(LAST_NUMBER, 0);
hsp.setSelectedPosition(lastPosition);
}
#Override
public void onPause() {
super.onPause();
if(hsp != null){
getSharedPreferences(CONTEXT).edit().putInt(LAST_NUMBER, hsp.getSelectedPosition()).commit();
}
}
If your headersState is enabled, use
SelectItemViewHolderTask task = new SelectItemViewHolderTask(positionX)
boolean isSmoothScroll = false // If you need to ignore the animation
task.setSmoothScroll(isSmothScroll)
setSelectedPosition(positionY, isSmothScroll, task)
However, if your headersState is disabled, then using this code will cause an exception: IllegalStateException: Cannot start headers transition.
In this case you need to use this instead:
getRowsSupportFragment().setSelectedPosition(positionY, isSmothScroll, task)
The difference between them is whether the HeadersSupportFragment is updated or not.
Related
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.
I have a SortedList being displayed in a RecyclerView by my RecyclerView.Adapter.
I use 2 custom Comparator instances from withing the SortedListAdapterCallback.compare() method to either sort A-Z or Z-A.
static class A2Z implements Comparator<Item> {
#Override
public int compare(Item t0, Item t1) {
return t0.mText.compareTo(t1.mText);
}
}
static class Z2A extends A2Z {
#Override
public int compare(Item t0, Item t1) {
return -1 * super.compare(t0, t1);
}
}
Item simply contains a single String mText;
I use my comparators in the SortedListAdapterCallback.compare() method:
private Comparator<Item> a2z = new A2Z();
private Comparator<Item> z2a = new Z2A();
private Comparator<Item> comparator = z2a;
#Override
public int compare(Item t0, Item t1) {
return comparator.compare(t0, t1);
}
I change the comparators on a button press. The list on screen does not update.
After logging values in the various methods, I can tell that the list itself is not updating. Notifying the adapter of changes simply redraws the old list, without resorting it.
So how do I force the underlying SortedList to resort all the items?
Perhaps it is best to just create a new Adapter each time, as in this question:
RecyclerView change data set
SortedList does not have functionality to resort itself - each instance only has a single sort order.
Went with creating a new adapter for each resort, as per Yigit's answer to the above referenced question:
If you have stable ids in your adapter, you can get pretty good
results (animations) if you create a new array containing the filtered
items and call
recyclerView.swapAdapter(newAdapter, false);
Using swapAdapter hints RecyclerView that it can re-use view holders.
(vs in setAdapter, it has to recycle all views and re-create because
it does not know that the new adapter has the same ViewHolder set with
the old adapter).
Use a switch statement inside the compare method with a local control flag (an enum is a good idea).
After changing the switch flag, call sortedList.replaceAll.
#Override
public int compare(PmpRole pmpRoleA, PmpRole pmpRoleB) {
switch (mSorter){
case IDX:
return pmpRoleA.getIdx().compareTo(pmpRoleB.getIdx());
case TITLE:
return pmpRoleA.getTitleIdx().compareTo(pmpRoleB.getTitleIdx());
case ID_IDX:
return pmpRoleA.getIdIdx().compareTo(pmpRoleB.getIdIdx());
}
return -1;
}
public void setSorter(Sorter sorter){
mSorter = sorter;
mPmpRoleSortedList.replaceAll(mPmpRoles);
}
Maintains animation functionality etc.
I have a RecyclerView whose adapter holds a SortedList of objects I can not modify.
My cards inside the RecyclerView should expand/collapse on click showing additional information when expanded. The problem is that there seems to be no way to store the information whether a card is expanded or collapsed since the ViewHolder gets recycled.
To make things more difficult, new items are added at the beginning and at the end of my adapter, so the positions change all the time. Even though new cards should be shown collapsed, they are sometimes shown as expanded when a ViewHolder of an expanded card gets recycled for the new card. This is when I tried to save the expand/collapse information in the ViewHolder directly.
The correct solution seems to be using a wrapper object with two properties: the original (unmodifiable) object, and a boolean indicating whether the item is expanded or collapsed.
Then in the onBindViewHolder() method of the RecyclerView's adapter, you have to set your views to expanded or collapsed depending on the state of the wrapper object.
#Override
public void onBindViewHolder(final ViewHolder ui, int position) {
if(wrapper_objects.get(position).expanded) {
expandView(ui);
} else {
collapseView(ui);
}
// expand/collapse on click
ui.expand.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(wrapper_objects.get(position).expanded) {
collapseView(ui);
wrapper_objects.get(position).expanded = false;
} else {
expandView(ui);
wrapper_objects.get(position).expanded = true;
}
}
});
}
An additional problem, but rare problem might be that an API sometimes returns the same objects that were already in the SortedList. In this case, they then overwrite the expand/collapse state in the wrapper object. A hackish solution I found for this is doing this:
private SortedList<WrapperObject> wrapper_objects = new SortedList<>(WrapperObject.class, new SortedList.Callback<WrapperObject>(){
#Override
public boolean areContentsTheSame(WrapperObject old, WrapperObject new) {
// keep state in new wrapper object
new.expanded = old.expanded;
return old.object.equals(new.object);
}
}
I have an ExpandableListView. Each child has a CheckBox and a TextView. When a user taps a child row, the CheckBox is supposed to change its state (checked vs unchecked). This works correctly if the user taps directly on the check box. However, if the user taps on the text view (same row, immediately to the right of the check box), I get a null pointer error as soon as I try to refer to the check box. Can anyone see what is wrong?
EDIT: After reading the suggestion below, I did some investigation and realized that I can implement my clickListener inside my adapter under getChildView(). This solves my issue with the null pointer as I can easily get a reference to the child view.
However, it creates another issue that I see no elegant solution to. Each time a child is clicked, I need to make changes to the listview itself. The data for this list resides in an ArrayList whose scope is within the Activity (not in the Adapter). If my clickListener is in the Adapter, how can I call back to the Activity to make changes to the ArrayList?
This strikes me as a catch-22. If I want to be able to manipulate my data, I can't get a reference to the child view. But if I want a reference to my child view, my data is out of scope, so I can't manipulate it. How do people resolve this? I must be missing something.
I'll throw in the relevant adapter code where you can see the beginning of my attempt to add a child onClickListener.
Thanks again!
public class Settings extends Activity {
//this is the list I need to access from the adapter if my click listener is there
private ArrayList<Categories> categoriesList = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_smart_settings);
db = new EventsDB(this);
expListGroups = new ArrayList<ExpandListGroup>();
setGroups();
/* Set up the data adapter */
expAdapter = new ExpandListAdapter(Settings.this, expListGroups);
populateExpandableGroups();
}
public void setGroups() {
/* Create lists of the individual line items */
categoriesList = db.getCategoriesForClient(client);
locationsList = db.getLocationsForClient(client);
/* Add an item to the locations list to allow the user to add a new location */
locationsList.add(new ClientSmartFinderLocations(client, "Add Location", null, false));
ExpandListGroup categoryGroup = new ExpandListCategory("Choose Categories", categoriesList);
ExpandListGroup locationGroup = new ExpandListLocation("Choose Locations", locationsList);
expListGroups.add(categoryGroup);
expListGroups.add(locationGroup);
}
private void populateExpandableGroups() {
expandableList = (ExpandableListView) findViewById(R.id.expandable_list);
expandableList.setAdapter(expAdapter);
//I've removed this section and moved it to the adapter, per my edit above
// expandableList.setOnChildClickListener(new OnChildClickListener() {
//
// #Override
// public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
//
// /* Update the finder setting for this client */
// String category = categoriesList.get(childPosition).getCategory();
// Boolean isSelected = !categoriesList.get(childPosition).getIsSelected();
// db.setClientCategory(client, category, isSelected);
//
// /* Update the check box to provide feedback to the user */
// View view = parent.getChildAt(childPosition - parent.getFirstVisiblePosition() + 1);
// CheckBox checkBox = (CheckBox) view.findViewById(R.id.check_box);
//
// //error occurs here
// checkBox.setChecked(!checkBox.isChecked());
// return true;
// }
// });
expAdapter.notifyDataSetChanged();
}
public class ExpandListAdapter extends BaseExpandableListAdapter {
//other methods
#Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View view, final ViewGroup parent) {
view = getCategoryChildView(groupPosition, childPosition, view);
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
TextView tv = (TextView) v.findViewById(R.id.expand_list_item);
CheckBox checkBox = (CheckBox) v.findViewById(R.id.check_box);
String category = tv.getText().toString();
Boolean isSelected = !checkBox.isSelected();
db = new EventsDB(context);
db.setClientCategory(client, category, isSelected);
checkBox.setChecked(!checkBox.isChecked());
//here I need to do some things that require me to manipulate the categoriesList from the Activity class - but it is out of scope
}
});
return view;
}
}
<CheckBox
android:id="#+id/check_box"
android:layout_marginLeft="30dp"
android:focusable="false"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="#+id/expand_list_item"
android:paddingLeft="10dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="#dimen/smart_finder_settings_font_size"
android:textColor="#FFFFFF" />
I think that I have a solution. If I create an instance of the Settings activity class within the Adapter, I can add the usual getter/setter methods to the Settings class. I can then call these methods from the adapter to get at that list, modify it, and then push it back to the Settings class, and all should be well.
It's a basic OOP approach, but the mental hangup for me was the idea of instantiating an activity. I don't know if this is common or not, but it seems weird to me. Anyone have a more elegant solution?
Within the Settings class:
public ArrayList<Categories> getCategoriesList() {
return categoriesList;
}
public void setCategoriesList(ArrayList<Categories> list) {
categoriesList = list;
}
Within the adapter:
Settings settings = new Settings();
ArrayList<Categories> tempCategoriesList = new ArrayList<Categories>();
tempCategoriesList = settings.getCategoriesList();
//make changes to the list
settings.setCategoriesList(tempCategoriesList);
You should set the checkbox checked state inside your ExpandListAdapter instead of accessing the view inside the ExpandableListView directly.
Im not a pro, so take that in mind. but what about storing the data you need the clicklistener to manipulate in a gobal application class? Maybe not the most elegant, but might work.
user55410 is on the right track. In your Settings() Activity, make categoryList static, then when you change it with the getter/setter methods from the new instance you create in your it will modify all instances of Settings.categoryList.
My project consists of a single Activity so far that loads a GridView that is populated by an extended BaseAdapter.
Typically the view is refreshed by calling BaseAdapter.notifyDataSetChanged() from one of my OnClickListener objects.
My problem is that I need to start a timer each time the view is refreshed. I only want to do this when the view has been completely reloaded.
I can't seem to find a listener or method that I can override in either the View or Adapter APIs to perform this, although I presume there is one.
The closest I've found is BaseAdapter.registerDataSetObserver although I'm not sure this is what I'm looking for either.
Can anyone advise please?
Thanks
DataSetObserver won't provide the feature you're looking for. In your adapter try looking at getView() or ViewBinder.setViewBinder() (for the Simple...Adapter classes) once the last view is filled with data you'll be able to know, roughly, when its done.
I'd say your best bet would be to create an anon inner class from this class and add your timer logic in an extension of GridView:
class AdapterDataSetObserver extends DataSetObserver {
#Override
public void onChanged() {
}
#Override
public void onInvalidated() {
}
}
(You can access this member variable as it is not priveate):
/**
* Should be used by subclasses to listen to changes in the dataset
*/
AdapterDataSetObserver mDataSetObserver;
This is the method that you should override (inside gridview) (You may need to make some modifications as some of these member variables may be private - mDataSetObserver is not, however:
#Override
public void setAdapter(ListAdapter adapter) {
if (null != mAdapter) {
mAdapter.unregisterDataSetObserver(mDataSetObserver);
}
resetList();
mRecycler.clear();
mAdapter = adapter;
mOldSelectedPosition = INVALID_POSITION;
mOldSelectedRowId = INVALID_ROW_ID;
if (mAdapter != null) {
mOldItemCount = mItemCount;
mItemCount = mAdapter.getCount();
mDataChanged = true;
checkFocus();
mDataSetObserver = new AdapterDataSetObserver();
mAdapter.registerDataSetObserver(mDataSetObserver);
mRecycler.setViewTypeCount(mAdapter.getViewTypeCount());
int position;
if (mStackFromBottom) {
position = lookForSelectablePosition(mItemCount - 1, false);
} else {
position = lookForSelectablePosition(0, true);
}
setSelectedPositionInt(position);
setNextSelectedPositionInt(position);
checkSelectionChanged();
} else {
checkFocus();
// Nothing selected
checkSelectionChanged();
}
requestLayout();
}
Look for these two lines in the method above and extend your class here:
mDataSetObserver = new AdapterDataSetObserver();
mAdapter.registerDataSetObserver(mDataSetObserver);