Android Layout Issue: Getting the Namespace Right

Question

OK. I have seen many questions along these lines, but it's possible that my issue is so basic (i.e. stupid n00b question), that no one has bothered to ask.

I'm still very new to Android programming, or using Java in an "industrial" capacity (i.e. not for simple 10-line classroom problems).

I have an activity class with an embedded static class:

package com.example.android.effectivenavigation;
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public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
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    public static class NonSwipeableViewPager extends ViewPager {
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    }
}

This comes from a sample from this site. What I am trying to do, is reduce it to the most basic, atomic elements.

Specifically, I want to have the entire example in the main activity file.

Here is my (non-funtional) XML:

<com.example.android.effectivenavigation.MainActivity.NonSwipeableViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Now, the problem is that when I specify the ViewPager in the layout XML, I get a "ClassNotFoundException" when it comes time to unwrap the NonSwipeableViewPager element.

It works fine if I set the NonSwipeableViewPager up in a separate file and reference it fairly directly. It's when it's embedded as a static class into the main activity class that I have issues.

I'm obviously using the wrong namespace in the XML.

Can anyone help me to find the correct namespace to use?

Thanks!

Answer 1

Try to have something like this in your main activity's xml:

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
                               xmlns:tools="http://schemas.android.com/tools"
                               android:id="@+id/pager"
                               android:layout_width="match_parent"
                               android:layout_height="match_parent"
                               tools:context="com.example.android.effectivenavigation.MainActivity.NonSwipeableViewPager"/>

Hope this helps.

Edit: I'm still new user and I am not used yet to how extensive my answers should be. So here is a bit more of an example of what I did:

You can extent Fragment in your custom class and have an onCreateView method in it. Also you should have a separate layout xml (in my example named fragment_example) for this fragment. The method should return a View object that inflates fragment's layout. Here is an example:

public static class ExampleFragment extends Fragment {

    static Button b;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_exmaple, container, false);

        b = (Button) rootView.findViewById(R.id.button1);

        b.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //do something
            }
        });

        return rootView;
    }

}

And here is the corresponding layout xml:

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          android:layout_width="match_parent"
          android:layout_height="fill_parent"
          android:orientation="vertical"
          tools:context=".activity_name">

          <Button
            android:layout_width="227dp"
            android:layout_height="40dp"
            android:text="Search"
            android:id="@+id/search"
            android:layout_gravity="center_horizontal"
            android:background="#80ffffff"
            android:textColor="#ffff6b6b"/>

 </LinearLayout>

You will also need an FragmentPagerAdapter class to create the fragments:

public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {

    public AppSectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int i) {
        switch (i) {

            default:
                return new ExampleFragment();
        }
    }

    @Override
    public int getCount() {
        return 1;
    }
}

Finaly in your activitys onCreate method you should have something like that:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Create the adapter that will return a fragment for each of the two primary sections
    // of the app.
    mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager, attaching the adapter and setting up a listener for when the
    // user swipes between sections.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mAppSectionsPagerAdapter);

}

Heavily based in this: http://developer.android.com/training/implementing-navigation/lateral.html

I hope this offers more detail and helps you more