Android FragmentPagerAdapter Example

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本文详细介绍了如何使用 Android FragmentPagerAdapter 实现滑动视图页面切换功能，包括代码实现、布局设计、适配器实现等关键步骤，适用于移动应用开发。

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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;
	}

}

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.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    android:padding="4dip" >

<android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="1" >
    </android.support.v4.view.ViewPager>

</LinearLayout>

<? xml version = "1.0" encoding = "utf-8" ?>

<LinearLayout xmlns : android = "http://schemas.android.com/apk/res/android"

android : layout_width = "match_parent"

android : layout_height = "match_parent"

android : gravity = "center_horizontal"

android : orientation = "vertical"

android : padding = "4dip" >

<android.support.v4.view.ViewPager

android : id = "@+id/pager"

android : layout_width = "match_parent"

android : layout_height = "0px"

android : layout_weight = "1" >

</android.support.v4.view.ViewPager>

<LinearLayout

android : layout_width = "match_parent"

android : layout_height = "wrap_content"

android : layout_weight = "0"

android : gravity = "center"

android : measureWithLargestChild = "true"

android : orientation = "horizontal" >

<Button

android : id = "@+id/first"

android : layout_width = "wrap_content"

android : layout_height = "wrap_content"

android : text = "First" >

</Button>

<Button

android : id = "@+id/last"

android : layout_width = "wrap_content"

android : layout_height = "wrap_content"

android : text = "Last" >

</Button>

</LinearLayout>

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;
	}
}

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.

<? xml version = "1.0" encoding = "utf-8" ?>

<RelativeLayout xmlns : android = "http://schemas.android.com/apk/res/android"

android : layout_width = "match_parent"

android : layout_height = "match_parent" >

<TextView

android : id = "@+id/text"

android : layout_width = "match_parent"

android : layout_height = "wrap_content"

android : gravity = "center_vertical|center_horizontal"

android : text = "@string/hello_world"

android : textAppearance = "?android:attr/textAppearanceMedium" />

<ImageView

android : id = "@+id/imageView1"

android : layout_width = "wrap_content"

android : layout_height = "wrap_content"

android : layout_below = "@+id/text"

android : layout_centerHorizontal = "true"

android : layout_marginTop = "36dp"

android : src = "@drawable/truiton" />

</RelativeLayout>

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<String>(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);
	}
}

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 <String> ( 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 :

<? xml version = "1.0" encoding = "utf-8" ?>

< LinearLayout xmlns : android = "http://schemas.android.com/apk/res/android"

android : layout_width = "match_parent"

android : layout_height = "match_parent"

android : background = "@android:drawable/gallery_thumb"

android : orientation = "vertical" >

< TextView

android : id = "@+id/text"

android : layout_width = "match_parent"

android : layout_height = "wrap_content"

android : gravity = "center_vertical|center_horizontal"

android : text = "@string/hello_world"

android : textAppearance = "?android:attr/textAppearanceMedium" / >

< FrameLayout

android : layout_width = "match_parent"

android : layout_height = "0dip"

android : layout_weight = "1" >

< ListView

android : id = "@android:id/list"

android : layout_width = "match_parent"

android : layout_height = "match_parent"

android : drawSelectorOnTop = "false" / >

< / FrameLayout >

< / LinearLayout >

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

Android FragmentPagerAdapter ImageFragment

Android FragmentPagerAdapter Sliding View

Android FragmentPagerAdapter TruitonListFragment

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.