Question

I’ve been trying to get 2 fragments work with a ViewPager with no success.. Here is the Main FragmentActivity which contains the ViewPager:

public class DownloadCenter extends android.support.v4.app.FragmentActivity {
    @Override
    protected void onCreate(Bundle arg0) {
        super.onCreate(arg0);
        setContentView(R.layout.download_center);
        ViewPager vp = (ViewPager) findViewById(R.id.DownloadCenter_viewPager);
        vp.setAdapter(new myAdapter(getSupportFragmentManager()));



    }

    public class myAdapter extends FragmentPagerAdapter {
        public myAdapter(FragmentManager fm) {
            super(fm);
        }

        Fragment[] fragmentArray = { Fragment.instantiate(DownloadCenter.this, Download_ImageQuality.class.getName()),
                Fragment.instantiate(DownloadCenter.this, Download_Tilawat.class.getName()) };

        @Override
        public Fragment getItem(int arg0) {
            return fragmentArray[arg0];
        }

        @Override
        public int getCount() {
            return fragmentArray.length;
        }


    }
}

Here is the logcat:

08-24 18:42:34.238: E/AndroidRuntime(4205): FATAL EXCEPTION: main
08-24 18:42:34.238: E/AndroidRuntime(4205): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test.test/test.test.DownloadCenter}: java.lang.ClassCastException: test.test.Download_ImageQuality cannot be cast to android.support.v4.app.Fragment
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2079)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2104)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread.access$600(ActivityThread.java:132)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1157)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.os.Looper.loop(Looper.java:137)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread.main(ActivityThread.java:4575)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at java.lang.reflect.Method.invokeNative(Native Method)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at java.lang.reflect.Method.invoke(Method.java:511)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at dalvik.system.NativeStart.main(Native Method)
08-24 18:42:34.238: E/AndroidRuntime(4205): Caused by: java.lang.ClassCastException: test.test.Download_ImageQuality cannot be cast to android.support.v4.app.Fragment
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.support.v4.app.Fragment.instantiate(Fragment.java:388)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.support.v4.app.Fragment.instantiate(Fragment.java:363)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at test.test.DownloadCenter$myAdapter.<init>(DownloadCenter.java:29)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at test.test.DownloadCenter.onCreate(DownloadCenter.java:18)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.Activity.performCreate(Activity.java:4465)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
08-24 18:42:34.238: E/AndroidRuntime(4205):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2033)
08-24 18:42:34.238: E/AndroidRuntime(4205):     ... 11 more

Download_ImageQuality header:

public class Download_ImageQuality extends android.support.v4.app.FragmentActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.download_imagequality);
                 .... //REST OF CLASS
        }
}

Answer 1

We can read from the documentation the following:

ViewPager is most often used in conjunction with Fragment, which is a
convenient way to supply and manage the lifecycle of each page. There
are standard adapters implemented for using fragments with the
ViewPager, which cover the most common use cases. These are
FragmentPagerAdapter, FragmentStatePagerAdapter, FragmentPagerAdapter,
and FragmentStatePagerAdapter; each of these classes have simple code
showing how to build a full user interface with them.

As you can see it talks about Fragments not FragmentActivities, the main difference between both of them is that a Fragment are the one that goes inside a FragmentActivity. You can think of them as:

FragmentActivity = Activity

Fragment = View

NOTE: Is not exactly as this, this is just an approximation for make it clearer.

So the best for you in this case is to use a FragmentPagerAdapter and make all the content of your ViewPager a Fragment, and the you can handle the full life cycle inside each page.