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Using multiple onClick methods in a single interface for RecyclerView

Context:
I've implemented a RecyclerView in my to-do list app.
I wanted to be able to use various onClick methods for items within the RecyclerView so I created an interface called onTaskListener.
This interface has two method stubs, one for onClick and one for onLongClick. In my ViewHolder, I implement both the onClick() and onLongClick() methods which simply pass off control to my onTaskClickListener().
In my adapter, I create an onTaskClickListener().
Then in my main activity, I implement the methods within onTaskClickListener().
My issue is that while my onTaskClick() works perfectly, my onTaskLongClick doesn't seem to function at all. Is there something wrong with the way I set up my RecyclerView/Adapter/ViewHolder/ViewModel pattern?
Question: If the way I have implemented my interface is wrong, how do I include multiple types of click events within a single interface?
Here are the relevant contents of each file (I know it's a lot, I'm very sorry for the wall of code):
onTaskClickListener.java:
public interface OnTaskListener {
void onTaskClick(int position); // Interfaces are implicitly abstract
void onTaskLongClick(int position);
}
itemViewHolder.java:
public class itemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
View itmView; // This is the general view
TextView txtView; // This is the specific text view that shows up as a singular task in the list of to-do tasks
OnTaskListener onTaskListener; // Create an OnTaskListener inside our view holder which allows the view holder to realize it's been clicked
public itemViewHolder(#NonNull View itemView, OnTaskListener inputOnTaskListener) {
super(itemView);
itmView = itemView;
txtView = itemView.findViewById(R.id.txtTask);
this.onTaskListener = inputOnTaskListener; // Take an onTaskListener that is passed into the object and store it internally
itemView.setOnClickListener(this); // passes the View.OnClickListener context to the itemView via "this"
}
#Override
public void onClick(View view) {
onTaskListener.onTaskClick(getAdapterPosition()); // This says that whenever we register a click event, we pass the logic onto the taskClick event
}
#Override
public boolean onLongClick(View view) {
onTaskListener.onTaskLongClick(getAdapterPosition()); // This says that whenever we register a longClick event, we pass the logic onto the taskClick event
return true; // This means that we have successfully consumed the long click event. No other click events will be notified
}
}
dataAdapter.java
public class dataAdapter extends RecyclerView.Adapter<itemViewHolder> {
List<taskItem> taskItemList;
private OnTaskListener onTaskListener;
public dataAdapter(List<taskItem> inputTaskItemList, OnTaskListener inputOnTaskListener){
this.taskItemList = inputTaskItemList;
this.onTaskListener = inputOnTaskListener;
}
#NonNull
#Override
public itemViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View localView = LayoutInflater.from(parent.getContext()).inflate(R.layout.taskholder, parent, false); //Don't even know what this line does, it's all so over my head
return new itemViewHolder(localView, onTaskListener); // Return an instance of whatever we made directly above this line
}
#Override
public void onBindViewHolder(#NonNull itemViewHolder holder, final int position) {
holder.txtView.setText(taskItemList.get(position).taskTitle);
// Look inside our ViewModel and get the text for this specific instance of the ViewModel, which corresponds to the current position
}
#Override
public int getItemCount() {
return taskItemList.size();
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity implements OnTaskListener{
private RecyclerView taskList; // Creates a RecyclerView to hook up to our RecyclerView widget in the UI
private dataAdapter localAdapter; // Instantiates our custom adapter class
List<taskItem> myItems; // Stores the items in a list of taskItem's
private RecyclerView.LayoutManager localLayoutManager; // God knows what this does :(
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
taskList = findViewById(R.id.taskList); // Connects our list from UI to recycler view code
localLayoutManager = new LinearLayoutManager(this); // assigns our localLayoutManager to an actual Layout Manager
taskList.setLayoutManager(localLayoutManager); // connecting our layout manager to our recycler view
taskList.setHasFixedSize(true);
myItems = new ArrayList<>(); // Now we FINALLY make our to-do list and populate it with actual tasks
myItems.add(new taskItem("groceries"));
myItems.add(new taskItem("practice bjj"));
localAdapter = new dataAdapter(myItems, this); // Pass the to do list to the adapter so it can feed it to the recycler view
taskList.setAdapter(localAdapter); // Lastly set the recycler view's adapter to the one we made above
}
#Override
public void onTaskClick(int position) {
taskItem currentTask = myItems.get(position);
if(!(currentTask.taskTitle.startsWith("Done: "))){ // Logic that marks a task as done on tap
currentTask.taskTitle = "Done: " + currentTask.taskTitle;
//logic that moves the tapped item to bottom of list
myItems.remove(position);
myItems.add(myItems.size(), currentTask);
localAdapter.notifyItemMoved(position, myItems.size());
}
else if(myItems.get(position).taskTitle.startsWith("Done: ")){ // Logic for if user taps a task already marked "done"
currentTask.taskTitle = currentTask.taskTitle.replaceFirst("Done: ", "");
myItems.set(position, currentTask); // Remove prefix
localAdapter.notifyItemChanged(position);
myItems.remove(position);
myItems.add(0, currentTask);
}
localAdapter.notifyDataSetChanged(); // Let the activity know that the data has changed
}
#Override
public void onTaskLongClick(int position) { // This branch deals with deleting tasks on long click
myItems.remove(position);
localAdapter.notifyItemRemoved(position); // Item has been deleted
}
}

You never call setOnLongClickListener():
public itemViewHolder(#NonNull View itemView, OnTaskListener inputOnTaskListener) {
super(itemView);
itmView = itemView;
txtView = itemView.findViewById(R.id.txtTask);
this.onTaskListener = inputOnTaskListener; // Take an onTaskListener that is passed into the object and store it internally
itemView.setOnClickListener(this); // passes the View.OnClickListener context to the itemView via "this"
// Add this line
itemView.setOnLongClickListener(this); // passes the View.OnLongClickListener context to the itemView via "this"
}
Alternatively, you can avoid going through this entirely by inlining the entire OnLongClickListener (and similarly for the OnClickListener):
itemView.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
onTaskListener.onTaskLongClick(getAdapterPosition()); // This says that whenever we register a longClick event, we pass the logic onto the taskClick event
return true; // This means that we have successfully consumed the long click event. No other click events will be notified
}
});
Thus avoiding having your itemViewHolder class implement the OnLongClickListener interface and making it impossible to forget to call setOnLongClickListener().

Custom View to be Used as a Nested View or as a RecyclerView Item view in Android

I'm new to android, but have a good JavaFX experience. I'm trying to create a custom view that i can reuse, but having a hard time figuring out the correct way to do it.
In javafx i could achieve this by: Creating a separate fxml file defining the layout of the custom view, then create a controller class linked to the fxml file, in that class, i'd have a method to retrieve the data model of the controller and use it to fill in the labels, etc.
The custom view i want would be
Constrained Layout
TextView (constrained to right anchor)
Round TextView (constrained to left anchor)
What is the best way to do this in android? Also, Is it possible to achieve this with a RecyclerView? If yes, how can i use a custom view for each item and set its data?

The question is broad. You may need additional research on creating views
Create a recyclerview in the main.xml,
a separate file with an item view.
You have 3 views in your item view - white background with margins (linearlayout?), right textView, and left textview.
The left textview should have android:background="drawable/round_shape" and round_shape.xml defined in your drawables folder. Everything is done in 3 xml files, main.xml for recyclerview, item.xml, round_background.xml. Then, the recyclerview adapter to bind the textviews with your array, and recyclerview initialization
A typical RV adaptor
public class MyRV extends RecyclerView.Adapter<MyRV.ViewHolder> {
private List<MyModelItemWith2Strings> mDataSet; // You may need to setup an array,
// with 2 String objects - for the right and left textviews
// Use an array of class with 2 elements rather than <String>, e.g. List<MyModelItemWith2Strings>
// pass your model here
// this setData will be used to provide the contents for the textviews
void setData(List< /* set your 2 string class here*/ > dataSet) {
mDataSet = dataSet;
}
static class ViewHolder extends RecyclerView.ViewHolder {
// Here you bind item TV's
// first you declare textviews that you will use to fill with data
// Add any other item views you will need to fill in
public TextView tv;
public TextView tv2;
public ViewHolder(LinearLayout v) {
super(v);
// Bind itemview views here. Put R.id.tv from your itemview.xml
tv = v.findViewById(R.id.....);
tv2 = v...
}
}
// Add your itemview layout here
#Override
public MyRV.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LinearLayout v = (LinearLayout) LayoutInflater.from(parent.getContext())
.inflate(/***R.layout.item_view***/, parent, false);
ViewHolder vh = new ViewHolder(v);
return vh;
}
#Override
public void onBindViewHolder( MyRV.ViewHolder h, int position) {
// get content from your model (the above list) and fill in the the itemview textviews
String a= mDataSet.get(position).getItem1();
String b = mDataSet.get(position). getItem2();
...
h.tv.setText(a);
// set clickers if you want to. The clicker class is below.
h.tv.setOnClickListener(new Click(position));
h.tv2.setText(...)
}
// This is obligatory to pass for your RV to initialize. It won't work if you don' t tell Android how to count your array soze
#Override
public int getItemCount() {
return mDataSet.size();
}
// These are my implementation of clickers. I prefer to put them in the nested class of the adapter.
private class Click implements OnClickListener {
private int pos;
Click(int position) {
pos = position;
}
#Override
public void onClick(View p1) {
// get data from your array on click
mDataSet.get(pos);
// Use pos as position on the array, mData.get(pos)
}
}
}
Then, in your main class set a recyclerview
RecyclerView rv = (RecyclerView) findViewById(R.id.rv_In_Main_Xml);
// just additional tunings.
rv.setHasFixedSize(true);
rv.setLayoutManager(new LinearLayoutManager(context)); // <- context = this, if you are in the Main activity
Then set the adapter
MyRV rva = new MyRV();
rva.setData(myArray_with_2_string_objects_to_fill_tvs);
rv.setAdaptor(rva);
And your recycler view gets filled with data

Null Pointer Exception when setting button visibility

I am getting to change the visibility of one of the buttons on my viewpager but I am getting a Null Pointer Exception on this line:
save_button.setVisibility(Button.INVISIBLE);
I am wondering why that is? Is it because I am not getting the visibility property inside of my InstantiateItem() for the button? Should I? If so, how do I change the button visibility based on the fact if the page is viewed by the user or not?
What I am trying to do is: Show the save button if all the views are viewed in the viewpager. If not all the views are viewed, then hide the save button.
Here is my code:
boolean isViewed = false;
boolean buttonState= false; //unpressed, if true == pressed
int buttonValue = 0;
//Methods
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.score_viewpager);
//Specify the number of pages/views
numberOfPages = new Integer[]{1, 2, 3, 4, 5};
final Button save_button = (Button) findViewById(R.id.save);
//Initialize adapter to populate view
myAdapter = new MyAdapter(ScoreCollectionPager.this, numberOfPages, save_button);
//Search view for viewpager Id and set the adapter on the first item
viewPager = (ViewPager) findViewById(R.id.viewPager);
viewPager.setAdapter(myAdapter);
viewPager.setCurrentItem(0);
//Attach the page change listener inside the activity
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
Button save_button = (Button) findViewById(R.id.save);
// This method will be invoked when the current page is scrolled
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
//This method will be invoked when a new page becomes selected
#Override
public void onPageSelected(int position) {
//get position
isViewed = true;
if (isViewed && (position == numberOfPages.length)) {
save_button.setVisibility(Button.VISIBLE);
}
else {
save_button.setVisibility(Button.INVISIBLE); // Null Pointer Exception here? why?
}
}
// Called when the scroll state changes:
// SCROLL_STATE_IDLE, SCROLL_STATE_DRAGGING, SCROLL_STATE_SETTLING
#Override
public void onPageScrollStateChanged(int i) {
//get state
}
});
}
private class MyAdapter extends PagerAdapter {
//fields
Button save_button;
//Constructor
public MyAdapter(Context context, numberOfPages, Button save_button) {
this.context = context;
this.numberOfPages = new ArrayList<Integer>(Arrays.asList(numberOfPages));
this.save_button = save_button;
}
//Returns total number of pages
#Override
public int getCount() {
return numberOfPages.size();
}
/**
* Create the page for the given position.
*
* #param parent The containing View in which the page will be shown.
* #param position The page position to be instantiated.
*
* #return Returns an Object representing the new page. This does not need
* to be a View, but can be some other container of the page.
*/
#Override
public Object instantiateItem(ViewGroup parent, final int position) {
//Get the inflater
LayoutInflater inflater = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
//inflate the root layout
View view = inflater.inflate(R.layout.score_collection, null);
//Save Button
save_button = (Button) view.findViewById(R.id.save);
save_button.setOnClickListener(new ViewGroup.OnClickListener() {
public void onClick(View view) {
//code for saving
}});
}
}

Move the below piece of code inside onPageSelected mehtod
Button save_button = (Button) findViewById(R.id.save);

I can see that Button instances are not the same. Make sure that you get the same object in the same layout. The first 2 buttons in your code belong to layout R.layout.score_viewpager, the last one belongs to R.layout.score_collection (in MyAdapter).

OK. It's a mess, but if you in onCreate give value to a class variable, you can access it in the other internal classes without having to call findViewById several times (expensive call).
Class var:
private final Button saveButton;
Set value in onCreate:
saveButton = (Button) findViewById(R.id.save);

java.lang.NullPointerException when try listview.getChildAt()

There is ListView with correct values:
public class FragmentTab1 extends SherlockFragment {
ListView list;
LazyAdapter adapter;
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
list = (ListView) getActivity().findViewById(android.R.id.list); //also I tried view.findViewById(android.R.id.list)
............
adapter = new LazyAdapter(getActivity(), mSource);
list.setAdapter(adapter);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View rootView = inflater.inflate(R.layout.fragmenttab1, container, false);
return rootView;
}
when I try:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId(); //correct
int itemCount = list.getCount(); // 10 ps as show Logcat
if (R.id.save == id) {
CheckBox cb;
for(int i = itemCount - 1; i >= 0; i--) {
cb = (CheckBox)list.getChildAt(i).findViewById(R.id.checkBox1); //Error here
}
}
return true;
}
xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<CheckBox
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Save to database"
android:id="#+id/checkBox1" /> // same id
and adapter is next:
public class LazyAdapter extends BaseAdapter {
private Activity activity;
ArrayList<Bitmap> bitmapArray = new ArrayList<Bitmap>();
private ArrayList<Data> mObjects;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public LazyAdapter(Activity a, ArrayList<Data> mObjects1) {
activity = a;
mObjects = mObjects1;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return mObjects.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
Data item = mObjects.get(position);
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.item_internet, null);
TextView text=(TextView)vi.findViewById(R.id.title1);
ImageView image=(ImageView)vi.findViewById(android.R.id.icon);
text.setText(item.getmTitle());
bitmapArray.add(imageLoader.getBitmap());
imageLoader.DisplayImage(item.getmImageUrl(), image);
return vi;
}
I receive correct ListView, but receive error when I try click save button from action bar.
Probably, I should init CheckBox in adapter?
Somebody can help me?

list.getChildAt(i) will be null if the child item is not visible. So check for null before use.
So you cannot retrieve all checked items in this way.
Please post complete .xml and the definition of <Data>.

I'd think you'd get an indexoutofbounds but since it's null, this might be why: ListView getChildAt returning null for visible children
Also, put a log statement in your for loop to display the value of all variables concerned, so: i and itemCount etc.
And set a breakpoint just before the loop and run debug mode to step over to check the values as it loops through and you'll see what i value caused the nullpointer in the debugger or if you miss it, it will be in logcat

I know this is very old post. But I'm answering because people are still looking for a work around on ListView getChildAt() null pointer exception.
This is because the ArrayApdater is REMOVING and RECYCLING the views that are not visible yet on the ListView because of height. So that if you have 10 item views, and ListView can display 4 - 5 at a the time :
The Adapter REMOVE the item views at position 5 to 9, so that any attempt to adapter.getChildAt(5... to 9) will cause null pointer exception
The Adapter also RECYCLE the item view, so that any reference you made on position 3 for example will be lost when you scroll down to 5 to 9, and also any Input that you make on position 3 (EditText, Checkbox, etc.) will be recycled when you scroll down to 5 to 9 and will be reused at another position later (ex position 1, 2 or 3, etc.) with the same value
The only way I found to control this is to forget about getting the View and to have :
Attribute HashMap<Integer, Boolean> cbValues or any type you want for handling the values you want to use for each item on the list. The first type must be unique for item like item->getId() or position. Initialize it with new HashMap<>() in the Constructor;
Add InputListener for Input Views, (addTextChangedListener for EditText, setOnCheckedChangeListener for Checkbox, etc.) And on input, update the HashMap key (item.getId() or position) and value (editable.toString() or true or false). Ex. on #Override public void onCheckedChanged, put boolean result cbValues.put(item.getId(), b);
Prevent Adapter from using recycled convertView, remove condition if(convertView == null) so that adapter always inflate a brand new view instance. Because the view instance is new each time, you must set the value from HashMap each time also like if it already contains the key if(cbValues.containsKey(item.getId())){cbItem.setChecked(cbValue.get(cbItem.getId()))};. Probably in this case there is not tons of Items, so that smooth scrolling won't be a must.
And finally create public methods to get the Values outside of Adapter passing item->getId() Integer as parameter. Ex : 'public bool getCheckboxValueForItemId(int itemId) { return cbValues.get(itemId); }` . It will be easy then to select Item from Adapter
Here is the Codes at the end :
public class LazyAdapter extends BaseAdapter {
private Activity activity;
ArrayList<Bitmap> bitmapArray = new ArrayList<Bitmap>();
private ArrayList<Data> mObjects;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
HashMap<Integer, Boolean> cbValues;
public LazyAdapter(Activity a, ArrayList<Data> mObjects1) {
activity = a;
mObjects = mObjects1;
cbValues = new HashMap<>();
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return mObjects.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
Data item = mObjects.get(position);
View vi=convertView;
// Remove convertView condition
//if(convertView==null)
vi = inflater.inflate(R.layout.item_internet, null);
TextView text=(TextView)vi.findViewById(R.id.title1);
ImageView image=(ImageView)vi.findViewById(android.R.id.icon);
Checkbox cbItem = (Checkbox) vi.findViewById(android.R.id.checkbox1);
text.setText(item.getmTitle());
bitmapArray.add(imageLoader.getBitmap());
imageLoader.DisplayImage(item.getmImageUrl(), image);
if(cbValues.containsKey(item.getId())) {
cbItem.setChecked(cbValue.get(cbItem.getId()))};
}
cbItem.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
cbValues.put(item.getId(), b);
}
});
return vi;
}
// itemId : unique identifier for an Item, not the position of Item in Adapter
public bool getCheckboxValueForItemId(int itemId) {
return cbValues.get(itemId);
}
}

Problems with global variable in inner OnItemClickListener class

I have an android fragment, that has a listview. for that listview I implemented an inner OnItemClickListener class.
When there's a click, I save the selection in a global variable called SelectedIndex.
If I click again on that list, I can see the previous selection correctly, So its saving the state on the global variable correctly.
The problem is when I try to access to that same global variable from another inner class, for example, one class used for listen to clicks on a button. Is always showing the value I used for initialize the varialbe (-1).
The code of the fragment:
/**
* A placeholder fragment containing the view for the recentCalls list
*/
public class RecentCallsFragment extends Fragment {
private Cursor cursorAllRows;
private RecentCallsTable rcTable;
private ListView list;
private RecentCallsAdapter adapter;
Button btnDelete, btnCreditRequest, btnCreditBlock, btnSendTo;
int selectedIndex; //this is the global variable that I am using.
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
rcTable = new RecentCallsTable(getActivity());
cursorAllRows = rcTable.getRecentCallsCursor();
adapter = new RecentCallsAdapter(getActivity(), cursorAllRows);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main, container, false);
list = (ListView) view.findViewById(R.id.listViewMain);
btnDelete = (Button) getActivity().findViewById(R.id.buttonDelete);
btnCreditRequest = (Button) getActivity().findViewById(R.id.buttonCr);
btnCreditBlock = (Button) getActivity().findViewById(R.id.buttonCRD);
list.setAdapter(adapter);
list.setOnItemClickListener(new ItemClickHandler()); //Add the inner ItemClickLister
btnSendTo = (Button) getActivity().findViewById(R.id.buttonSendTo);
btnSendTo.setOnClickListener(new DebugOnClick());//here I add the inner clicklister
return view;
}
/**
* Class that handles the one click action on the list
*/
public class ItemClickHandler implements AdapterView.OnItemClickListener{
//when there's one fast click, keep the selection on the item or remove it if already has it
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
int prevSelection = adapter.getSelectedIndex();
Toast.makeText(getActivity(), Integer.toString(selectedIndex), Toast.LENGTH_SHORT).show();
int newSelection = position;
if(prevSelection == position){
newSelection = -1;
}
selectedIndex = newSelection; //here I change the value of the global variable
adapter.setSelectedIndex(newSelection);
adapter.notifyDataSetChanged();
}
}
public class DebugOnClick implements View.OnClickListener{
public DebugOnClick(){
}
#Override
public void onClick(View view) {
Toast.makeText(getActivity(), Integer.toString(selectedIndex), Toast.LENGTH_SHORT).show(); //here I show the value of the global variable and is always -1
}
}
}
Which may be the problem?

There is one possibility that comes into my mind. When you have an inner class instantiated it implicitly binds with an instance of the hosting class (as if it were a reference of the hosting class). So I assume that the inner classes that you use are each linked with a different instance of the hosted class and thus using a different selectedIndex. Your global variable is not really global, its an instance variable.

I just found the problem. The buttons are in the main activity, so I just moved the global variable to the main Activity and started to manipulate it from the fragments like this:
MainActivity ma = (MainActivity) getActivity();
ma.rcSelected = newSelection;