Develop Reference

Creating a generic PagedListAdapter using android paging library

My app has more than 4 lists of different data models.
I want to create a more generic CommonAdapter that extends PagedListAdapter
Here is my current code
public abstract class CommonPagedListAdapter<T, VH extends RecyclerView.ViewHolder>
extends PagedListAdapter<T, VH> {
private Context mContext;
private ArrayList<T> mArrayList;
public abstract void onItemClick(T model, int position);
public abstract int getLayoutResId();
protected CommonPagedListAdapter(Context context, ArrayList<T> arrayList,
#NonNull DiffUtil.ItemCallback<T> diffCallback) {
super(diffCallback);
this.mContext = context;
this.mArrayList = arrayList;
}
#NonNull
#Override
public VH onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
//what should i return here?
View view = LayoutInflater.from(mContext).inflate(getLayoutResId(),parent,false);
return (VH) new ItemViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull VH holder, int position) {
//what should i do here?
// holder
}
class ItemViewHolder extends RecyclerView.ViewHolder {
public ItemViewHolder(#NonNull View itemView) {
super(itemView);
}
}
}
I'm using PagelListAdapter from the Android Paging Library
I would like to know a few things:
- What should be set in the onCreateViewHolder as I'll be having different ViewHolders?
- What should be set in onBindViewHolder?
- Is this really the right way that makes the CommonPagedListAdapter extensible and maintainable?

I had a similar issue where I tried to create a single adapter to use for multiple different list types. I ultimately came to the conclusion that it is best to use a separate adapter for each list type solely because it avoids having to make a very big "common" adapter class which goes against the "single-responsibility" principle. That way, each adapter is a lot smaller, more maintainable, and flexible.
However, if you really want to use a single adapter for similar items, the way I usually do it is by creating unique ViewHolders for each item type and then binding them accordingly in onBindViewHolder using a switch statement or something similar. In order to do this, you would need to override an additional method called getItemViewType in your adapter.
There's a really good guide that goes over how to create an adapter that can handle different view types on Codepath: https://guides.codepath.com/android/Heterogenous-Layouts-inside-RecyclerView

Is it possible to write a view wrapper？

Now，I want to replace all view by my own AppCompatDelegate.
And override method createView so that I can update all the views in project.
Now I can do update like this:
public class UpdatedView extends View
in AppCompatDelegate :
public View createView(String name) {
if ("View".equals(name)) {
return UpdatedView();
}
}
Now, the problem I'm facing is that is it possible to create a view wrapper for all View. So that I can write like this
public class ViewWrapper extends View{
View realView;
#Override
public void methods() {
//override the method which is need, like ondraw, onClick
doUpdateThings();
realView.methods();
}
}
wrapper all views like this.
public View createView(String name) {
if ("View".equals(name)) {
return UpdatedViewWrapper(new View());
}
}
I want to know whether it's possible or not, and safe or not.
Someting added: it seems, I don't need the replace delegate but override onCreateView is enough.

How to create an interface between an adapter and a viewholder

I want to create an interface between an adapter and a view holder (this view holder is an inner class of another adapter) so that I can update the text view (number). How can I do this?
In detail:
I have two recycle views (Main List Recycler View and Sub List Recycler View horizontally placed as shown in the fig) one having a number (as one of its item) and other having checkbox (as its item).
I have two adapters FilterMainListAdapter and FilterSubListAdapter with view holders FilterMainListViewHolder and FilterSubListViewHolder populating the fields.
When checkboxes are selected in the Sub List Recycler View, I want the corresponding number in the Main List Recycler View to update.
For this, I'm using and Interface.
public interface ChangeFilterMainNumber {
void OnChangeFilterMainNumberListener(int totalCheckedNumber);
}
I've checkbox's onClick method inside the FilterSubListViewHolder and I'm trying to send the total check boxes checked number as follows.
changeFilterMainNumber.OnChangeFilterMainNumberListener(totalCheckedNumber);
After that, I'm implementing ChangeFilterMainNumber interface inside the FilterMainListViewHolder
public class FilterMainListViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener,
ChangeFilterMainNumber {...}
But How can I define this interface inside the FilterSubListAdapter?
changeFilterMainNumber = ???;
[If it is an activity one can define the interface like this changeFilterMainNumber = (ChangeFilterMainNumber) context inside the default constructor of FilterSubListAdapter. But what about a view holder that is an inner class of another adapter?]
or is there a better approach in finding a solution to my problem other than this?
Update: You can take a look at the code here https://github.com/gSrikar/FilterScreen

If I implement the function as you want, I will implement like this:
(This is like an Observer pattern)
class Fragment/Activity implement OnChangeFilterMainNumberListener{
FilterMainListAdapter mainAdapter;
FilterSubListAdapter subAdapter;
void oncreate() {
mainAdapter = new FilterMainListAdapter(this);
}
#Override
void OnChangeFilterMainNumberListener(int totalCheckedNumber) {
.....
// Update data to sub list
}
}
class FilterMainListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
public interface ChangeFilterMainNumber {
void OnChangeFilterMainNumberListener(int totalCheckedNumber);
}
ChangeFilterMainNumber listener;
FilterMainListAdapter(ChangeFilterMainNumber listener) {
this.listener = listener;
}
#Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
item.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(listener != null) {
listener.OnChangeFilterMainNumberListener(position)
}
}
});
}
}
class FilterSubListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
}

Android Annotations: custom view inheritance?

I'm trying to create a custom view that has a content area and a progress bar so that any inheriting custom view would have it's layout inflated in the content area. That way you could show/hide the progress bar on the child view.
#EViewGroup(R.layout.loading_view)
class LoadingView extends RelativeLayout{
// some code
#ViewById FrameLayout content;
#ViewById ProgressBar pb;
public View getFrameLayout(){
// sub-classes will use this to inject their content
return content;
}
void setIsLoading(boolean l){
// shows\hides pb
}
}
#EViewGroup(R.layout.other_view)
class OtherView extends LoadingView{
#ViewById TextView someTxt;
public OtherView(...){
// inject to getFrameLayout()
}
}
Now this doesn't remotely work. Here is why:
#EViewGroup on OtherView overrides the one on LoadingView so R.layout.loading_view doesn't even gets loaded. it only gets loaded if you specify #EViewGroup(R.layout.loading_view)
if you do specify the same layout , there is no point in having Android Annotations in the first place since it will not inject view in OtherView.
Is there any way at all to make this work ? Any ideas ?

If I have understood you correctly, you could solve overriding the method:
#EViewGroup(R.layout.loading_view)
class LoadingView extends RelativeLayout {
// some code
#ViewById FrameLayout content;
#ViewById ProgressBar pb;
public View getFrameLayout(){
return content;
}
void setIsLoading(boolean l){
// shows\hides pb
}
}
And each child implement the method returning its content:
class OtherView extends LoadingView {
#ViewById TextView someTxt;
#Override
public View getFrameLayout() {
View content = inflate(R.layout.other_view);
return content;
}
}
As you said, If you put #EViewGroup(R.layout.other_view) in child class, AndroidAnnotations overwrite the main layout view.

How to use #ViewById for an inflated view outside of #EActivity(R.layout.activity_x)

I am using Android Annotations 3.1 in my project in Android Studio and I am using an Expandable List View.
I am adding a header to my list like this:
View header = getLayoutInflater().inflate(R.layout.list_view_header, null);
txt_user = (TextView) header.findViewById(R.id.txt_user);
txt_user.setText(" ... ");
mExpandableListView.addHeaderView(header);
Question:
How can I use #ViewById to set my TextView to:
- avoid using findViewById
- changing its text
- and then adding that as a header during:
#AfterViews
protected void init() {
....
}
If I do this inside my Activity when using my text view inside init:
#ViewById
TextView txt_user;
It gives null pointer exception.

Why don't you create a custom view like this :
#EViewGroup(R.layout.list_view_header)
public class MyHeader extends LinearLayout {
#ViewById(R.id.txt_user)
protected TextView mTextView;
public void setText(String text) {
mTextView.setText(text);
}
public MyHeader(Context context) {
super(context);
}
}
Then, in your Activity, write this :
#EActivity(R.layout.activity_xxx)
public class MyActivity extends Activity {
private MyHeader mHeader;
#AfterViews
protected void init() {
mHeader = MyHeader_.build(this);
mHeader.setText("...");
mExpandableListView.addHeaderView(mHeader);
}
}

To use a view signed with #ViewGroup within a layout, you need to implement the constructors that take AttributSet in its class.
NOTE: Remember to use the generated class that has a _ (underline) at the end.
She who must be declared in the layout xml.