PagerAdapter Archives - Truiton

Android FragmentPagerAdapter vs FragmentStatePagerAdapter

Mohit Gupt — Tue, 04 Jun 2013 19:35:33 +0000

To develop an app in Android with sliding views, a variation of PagerAdapter class along with ViewPager class is used. Recently I wrote two tutorials about PagerAdapter classes, describing Android FragmentPagerAdapter and FragmentStatePagerAdapter, as both of them have benefits of their own. This Android FragmentPagerAdapter vs FragmentStatePagerAdapter is my concluding article on PagerAdapter series. In this article I will compare both PagerAdapters and explain the perfect situation for their use. If you wish to read my complete series on PagerAdapters and ViewPagers have a look at links below:

To compare Android FragmentPagerAdapter vs FragmentStatePagerAdapter, first lets understand what Android FragmentPagerAdapter does. FragmentPagerAdapter is used along with ViewPager class, to display sliding fragments. ViewPager class is a sort of layout manager which provides the functionality of flipping data in form of pages, left and right. In simple words ViewPager class provides the functionality to flip pages in an app. Moving forward with this basic info, to understand the Android FragmentPagerAdapter vs FragmentStatePagerAdapter lets try to understand the technical aspect of Android FragmentPagerAdapter.

Android FragmentPagerAdapter is type of PagerAdapter which populates the data inside the ViewPager, which in turn allows the flipping of data in form of pages. Usually to display sliding fragments two methods of FragmentPagerAdapter are used, getCount and getItem. The first one returns the number of fragments to be displayed, and the second one is used to display the actual fragment. To understand the code have a look at my tutorial about Android FragmentPagerAdapter. The purpose for using this type of fragment adapter is to keep the whole fragment in memory. Its view hierarchy may be destroyed but the fragment may still remain in memory. Hence it is advised to use this Android FragmentPagerAdapter only when there are low number of static fragments, since all fragments would be kept in the memory and this would increase the memory heap. Which could result a slow running app.

Further to understand Android FragmentPagerAdapter vs FragmentStatePagerAdapter, lets try to understand the FragmentStatePagerAdapter. This adapter also falls under the PagerAdapter class and is used with ViewPager to display sliding views. It also has same methods getCount and getItem. Which are used to get the fragment count and get the fragment reference respectively, same as in FragmentPagerAdapter. To further understand the code part of it please read my tutorial on Android FragmentStatePagerAdapter. The main functionality for which FragmentStatePagerAdapter is used, to accommodate a large number of fragments in ViewPager. As this adapter destroys the fragment when it is not visible to the user and only savedInstanceState of the fragment is kept for further use. This way a low amount of memory is used and a better performance is delivered in case of dynamic fragments.

Android FragmentPagerAdapter vs FragmentStatePagerAdapter

Now that I have explained what FragmentStatePagerAdapter and FragmentPagerAdapter does, lets finally discuss Android FragmentPagerAdapter vs FragmentStatePagerAdapter. As I explained FragmentPagerAdapter stores the whole fragment in memory, and could increase a memory overhead if a large amount of fragments are used in ViewPager. In contrary its sibling, FragmentStatePagerAdapter only stores the savedInstanceState of fragments, and destroys all the fragments when they lose focus. Therefore FragmentStatePagerAdapter should be used when we have to use dynamic fragments, like fragments with widgets, as their data could be stored in the savedInstanceState. Also it wont affect the performance even if there are large number of fragments. In contrary its sibling FragmentPagerAdapter should be used when we need to store the whole fragment in memory. When I say the whole fragment is kept in memory it means, its instances wont be destroyed and would create a memory overhead. Therefore it is advised to use FragmentPagerAdapter only when there are low number of fragments for ViewPager. It would be even better if the fragments are static, since they would not be having large amount of objects whose instances would be stored. Hope this clears out the difference between Android FragmentPagerAdapter and FragmentStatePagerAdapter. If you like this article please share it with your friends on Google+ and Facebook, also like our page on Facebook for latest updates.

Mohit Gupt

Born in New Delhi, India. A software engineer by profession, an android enthusiast and mobile development evangelist. My motive here is to create a group of skilled engineers, who can build better software. Reason being programming is my passion, and also it feels good to make a device do something you want. Professionally I have worked with many software engineering and product development firms. As of now too, I am employed as a senior engineer in a leading tech company. In total I may have worked on more than 20 projects professionally, but whenever I get spare time I share my thoughts here at Truiton.

www.truiton.com

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Android FragmentPagerAdapter Example

Mohit Gupt — Fri, 31 May 2013 12:04:21 +0000

How cool is it to have an app which has swipe views, it makes app interactive and fun to use, right? So being a mobile app consultant at Truiton I was working on an app where segmented forms were to be filled by user. I thought why not use swipe tabs and sliding views. I searched and found this can be implemented by Android ViewPager class, which is used in conjunction with Android FragmentPagerAdapter class or Android FragmentStatePagerAdapter class. Since any sort of software development requires precision and accuracy in work my purpose was solved by the later one. Still I decided to write a tutorial about Android FragmentPagerAdapter Example.

There are two ways to implement Android ViewPager class, but this tutorial only focuses on Android FragmentPagerAdapter with an example. Now since both adapters have different ways of working, you might want to read about the other one too, have a look at my series on PagerAdapters :

In my previous tutorial I mentioned a case, if we wish to keep the fragment in the memory. Here steps in Android FragmentPagerAdapter, the main advantage of using Android FragmentPagerAdapter is that, it keeps the fragment in memory. This definitely increases the memory usage, therefore it is advised to use Android FragmentPagerAdapter only when there are less number of fragments. If you app has non changing fragments like, fragments with images or static text it might work even better. But using Android FragmentPagerAdapter for large number of fragments would result choppy and laggy UX.

Android FragmentPagerAdapter Example

Lets start with the main activity, this activity is where the Android FragmentPagerAdapter class is declared. Have a look at MainActivity.java.

package com.truiton.fragmentpageradapter;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends FragmentActivity {
 static final int ITEMS = 10;
 MyAdapter mAdapter;
 ViewPager mPager;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.fragment_pager);
 mAdapter = new MyAdapter(getSupportFragmentManager());
 mPager = (ViewPager) findViewById(R.id.pager);
 mPager.setAdapter(mAdapter);

 Button button = (Button) findViewById(R.id.first);
 button.setOnClickListener(new OnClickListener() {
 public void onClick(View v) {
 mPager.setCurrentItem(0);
 }
 });
 button = (Button) findViewById(R.id.last);
 button.setOnClickListener(new OnClickListener() {
 public void onClick(View v) {
 mPager.setCurrentItem(ITEMS - 1);
 }
 });
 }

 public static class MyAdapter extends FragmentPagerAdapter {
 public MyAdapter(FragmentManager fragmentManager) {
 super(fragmentManager);
 }

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

 @Override
 public Fragment getItem(int position) {
 switch (position) {
 case 0: // Fragment # 0 - This will show image
 return ImageFragment.init(position);
 case 1: // Fragment # 1 - This will show image
 return ImageFragment.init(position);
 default:// Fragment # 2-9 - Will show list
 return TruitonListFragment.init(position);
 }
 }
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
 // Inflate the menu; this adds items to the action bar if it is present.
 getMenuInflater().inflate(R.menu.main, menu);
 return true;
 }

}

In the above class one can see that MainActivity extends FragmentActivity and in this class, both MyAdapter and ViewPager class are instantiated. If you look closely you would find that MyAdapter class extends Android FragmentPagerAdapter class. Lets have a look at the extended Android FragmentPagerAdapter class, here exists a method by the name of getItem. This getItem method is the one which calls all the fragments which are to be displayed according to the position. MainActivity.java is displayed by layout fragment_pager.xml.

Above is the main layout where all fragments would be displayed. Have a look at android.support.v4.view.ViewPager tag, since this tag is used here, this app would run on android devices lower than API version 11 too. Next lets have a look at ImageFragment.java.

package com.truiton.fragmentpageradapter;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class ImageFragment extends Fragment {
	int fragVal;

	static ImageFragment init(int val) {
		ImageFragment truitonFrag = new ImageFragment();
		// Supply val input as an argument.
		Bundle args = new Bundle();
		args.putInt("val", val);
		truitonFrag.setArguments(args);
		return truitonFrag;
	}

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		fragVal = getArguments() != null ? getArguments().getInt("val") : 1;
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		View layoutView = inflater.inflate(R.layout.fragment_image, container,
				false);
		View tv = layoutView.findViewById(R.id.text);
		((TextView) tv).setText("Truiton Fragment #" + fragVal);
		return layoutView;
	}
}

In the above class a static method by the name of init is declared. This init method is called in the extended Android FragmentPagerAdapter class with position of the fragment as argument. This argument is later on used in onCreate and onCreateView method of this ImageFragment. The layout file for this class is fragment_image.xml.

Now have a look at the second type of fragment used in Android FragmentPagerAdapter Example, TruitonListFragment.java.

package com.truiton.fragmentpageradapter;

import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class TruitonListFragment extends ListFragment {
 int fragNum;
 String arr[] = { "This is", "a Truiton", "Demo", "App", "For", "Showing",
 "FragmentPagerAdapter", "and ViewPager", "Implementation" };

 static TruitonListFragment init(int val) {
 TruitonListFragment truitonList = new TruitonListFragment();

 // Supply val input as an argument.
 Bundle args = new Bundle();
 args.putInt("val", val);
 truitonList.setArguments(args);

 return truitonList;
 }

 /**
  * Retrieving this instance's number from its arguments.
  */
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 fragNum = getArguments() != null ? getArguments().getInt("val") : 1;
 }

 /**
  * The Fragment's UI is a simple text view showing its instance number and
  * an associated list.
  */
 @Override
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
 Bundle savedInstanceState) {
 View layoutView = inflater.inflate(R.layout.fragment_pager_list,
 container, false);
 View tv = layoutView.findViewById(R.id.text);
 ((TextView) tv).setText("Truiton Fragment #" + fragNum);
 return layoutView;
 }

 @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 super.onActivityCreated(savedInstanceState);
 setListAdapter(new ArrayAdapter(getActivity(),
 android.R.layout.simple_list_item_1, arr));
 }

 @Override
 public void onListItemClick(ListView l, View v, int position, long id) {
 Log.i("Truiton FragmentList", "Item clicked: " + id);
 }
}

In the above class, the only difference is, that ListFragment is used, rest is same as in ImageFragment. It has a static init method which is called from extended Android FragmentPagerAdapter. It uses layout fragment_pager_list.xml :

After defining all the classes and layouts your app should look like screenshots below

In this tutorial I defined a class which extended FragmentActivity, and instantiated extended version of Android FragmentPagerAdapter and ViewPager. This whole Android FragmentPagerAdapter example is made with support library, hence this would run on all android devices. Again to sum up, I would say that use Android FragmentPagerAdapter only when you have low amount of fragments that you want to keep in memory. Otherwise it will create a memory overhead and affect your app’s performance. This would work even better with non changing fragments. If you still have concerns on which PagerAdapter to use, have a look at Android FragmentPagerAdapter vs FragmentStatePagerAdapter. Hope this helped you out, if it did please like and share this with your friends on Google+ and Facebook. Also like our Facebook page for updates.

Mohit Gupt

www.truiton.com

The post Android FragmentPagerAdapter Example appeared first on Truiton.