Inflate custom class inside Pager Adapter

Question

I am working on a project where I need to implement an infinite scrolling pager adapter. While I have found useful links to implement a two way infinite scrolling view pager similar to the CalendarView( similar in terms of functionality), I am stuck with a small problem. Please have a look the code here.

Is there a way where I can replace this inside my adapter (extending PagerAdapter)

    @Override
        public Object instantiateItem (ViewGroup container, int position){
            LayoutInflater inflater = (LayoutInflater) container.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View mPage = inflater.inflate(R.layout.page_layout,null);
             container.addView(mPage );
            return mPage ;
            }

With this

    @Override
    public Object instantiateItem (ViewGroup container, int position){

       PageLayout page= new PageLayout(context, Integer i, String str);
        container.addView(page);
        return page;

    }

Where

    public class PageLayout extends LinearLayout {

    Integer i;
    String str;

       public PageLayout (Context context, Integer i, String str) {
       super(context);
       View v = inflate(context,R.layout.page,null);
       this.i =i; 
       this.str =str;
       //Find TextViews etc and set them.
       //Perform an asynctask and some other cool stuff

       }
    }

So what I need here, is a way to inflate the view extending a LinearLayout ViewGroup in a method within the view class. I need to do this because I want to initialize the Custom View with a few member variables through a constructor and use the same constructor to inflate the layout with the member variables. When I tried this code and debugged the code, the view member of the page is null. Is there a way to do it this way? Am I missing something? Thanks for your help.

Edit

The custom view PageLayout has a constructor which takes in a few parameters. PageLayout needs those variables to do perform an asynctask.

Answer 1

The basic idea is to create a xml layout where you use your custom view.

row.xml could look like that:

<my.awesome.package.name.PageLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <!-- just put more useful views here -->
</my.awesome.package.name.PageLayout>

You can then easily use it in your PageAdapter like this:

@Override
public Object instantiateItem (ViewGroup container, int position){
    LayoutInflater inflater = LayoutInflater.from(container.getContext());
    PageLayout mPage = (PageLayout) inflater.inflate(R.layout.row, container);
    mPage.init("param1", 123); // pass some data to set up the layout
    // to some stuff with other views
    // Also read about ViewHolder pattern if you do not know what it is
    return mPage;
}

The error message Expected resource of type layout does not mean: because the ID is not set yet. The problem is that getId() of a layout gives you the R.id.* kind of ID and not the kind of R.layout.*. Check the generated R class to see that layout and id are different classes and inflate() requires R.layout.* ids.

Update:

Your PageLayout can look like that:

public class PageLayout extends RelativeLayout {
    public PageLayout(Context context) {
        super(context);
    }

    public PageLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public PageLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public void init(String param1, int param2) {
       // here you can call findViewById(R.id.some_internal_view_ids)
       // and to what ever you want with the parameter
    }
}

With that you can access every view you have added inside your PageLayout in your row.xml. For more details I suggest you read the doc about Creating Custom Views