Tutorial to implement the use of TabHost in Android 2.2 + ViewPager and Fragments-ThrowExceptions

Exception or error:

A short tutorial for people like me who had some trouble finding a way to implement TabHost and ViewPager, including page swiping with fingers and tab click to change pages. The shown solution is compatible with Android versions 2.2+.

It includes Tabs initialization, ViewPager connected with Tabs and Page Scrolling management.

Its main peculiarity is the optimization for earlier versions of Android (Android 2.2 (Froyo), API version 8) and the simple implementation for different purposes.

How to solve:

The tutorial includes 4 classes and 2 layouts. It has been tested with an Android phone 2.2, and you can just copy & paste to try it.

MainActivity.java (the main activity):

package samples.tabhost.andreaoid.net;

import java.util.ArrayList;
import java.util.List;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.widget.TabHost;
import android.widget.TabHost.OnTabChangeListener;

public class MainActivity extends FragmentActivity implements OnTabChangeListener, OnPageChangeListener {

    MyPageAdapter pageAdapter;
    private ViewPager mViewPager;
    private TabHost mTabHost;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mViewPager = (ViewPager) findViewById(R.id.viewpager);

        // Tab Initialization
        initialiseTabHost();

        // Fragments and ViewPager Initialization
        List<Fragment> fragments = getFragments();
        pageAdapter = new MyPageAdapter(getSupportFragmentManager(), fragments);
        mViewPager.setAdapter(pageAdapter);
        mViewPager.setOnPageChangeListener(MainActivity.this);
    }

    // Method to add a TabHost
    private static void AddTab(MainActivity activity, TabHost tabHost, TabHost.TabSpec tabSpec) {
        tabSpec.setContent(new MyTabFactory(activity));
        tabHost.addTab(tabSpec);
    }

    // Manages the Tab changes, synchronizing it with Pages
    public void onTabChanged(String tag) {
        int pos = this.mTabHost.getCurrentTab();
        this.mViewPager.setCurrentItem(pos);
    }

    @Override
    public void onPageScrollStateChanged(int arg0) {
    }

    // Manages the Page changes, synchronizing it with Tabs
    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        int pos = this.mViewPager.getCurrentItem();
        this.mTabHost.setCurrentTab(pos);
    }

    @Override
        public void onPageSelected(int arg0) {
    }

    private List<Fragment> getFragments(){
        List<Fragment> fList = new ArrayList<Fragment>();

        // TODO Put here your Fragments
        MySampleFragment f1 = MySampleFragment.newInstance("Sample Fragment 1");
        MySampleFragment f2 = MySampleFragment.newInstance("Sample Fragment 2");
        MySampleFragment f3 = MySampleFragment.newInstance("Sample Fragment 3");
        fList.add(f1);
        fList.add(f2);
        fList.add(f3);

        return fList;
    }

    // Tabs Creation
    private void initialiseTabHost() {
        mTabHost = (TabHost) findViewById(android.R.id.tabhost);
        mTabHost.setup();

        // TODO Put here your Tabs
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab1").setIndicator("Tab1"));
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab2").setIndicator("Tab2"));
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab3").setIndicator("Tab3"));

        mTabHost.setOnTabChangedListener(this);
    }
}

MyPageAdapter.java (fragment manager):

package samples.tabhost.andreaoid.net;

import java.util.List;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

public class MyPageAdapter extends FragmentPagerAdapter {
    private List<Fragment> fragments;

    public MyPageAdapter(FragmentManager fm, List<Fragment> fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int position) {
        return this.fragments.get(position);
    }

    @Override
    public int getCount() {
        return this.fragments.size();
    }
}

MyTabFactory (tab manager):

package samples.tabhost.andreaoid.net;

import android.content.Context;
import android.view.View;
import android.widget.TabHost.TabContentFactory;

public class MyTabFactory implements TabContentFactory {

    private final Context mContext;

    public MyTabFactory(Context context) {
        mContext = context;
    }

    public View createTabContent(String tag) {
        View v = new View(mContext);
        v.setMinimumWidth(0);
        v.setMinimumHeight(0);
        return v;
    }
}

MySampleFragment.java (the single fragment – included for demonstration purposes):

package samples.tabhost.andreaoid.net;

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 MySampleFragment extends Fragment {

    private static View mView;

    public static final MySampleFragment newInstance(String sampleText) {
        MySampleFragment f = new MySampleFragment();

        Bundle b = new Bundle();
        b.putString("bString", sampleText);
        f.setArguments(b);

        return f;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        mView = inflater.inflate(R.layout.sample_fragment, container, false);
        String sampleText = getArguments().getString("bString");

        TextView txtSampleText = (TextView) mView.findViewById(R.id.txtViewSample);
        txtSampleText.setText(sampleText);

        return mView;
    }
}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TabHost
        android:id="@android:id/tabhost"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >
        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >
            <TabWidget
                android:id="@android:id/tabs"
                android:orientation="horizontal"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_weight="0" />
            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="0dp"
                android:layout_height="0dp"
                android:layout_weight="0" />
            <android.support.v4.view.ViewPager
                android:id="@+id/viewpager"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_gravity="bottom" />
        </LinearLayout>
    </TabHost>
</RelativeLayout>

sample_fragment.xml (you can put here your fragment layout):

<?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"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/txtViewSample"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:text="" />

</RelativeLayout>

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