ClassCastException: cannot be cast to android.support.v4.app.Fragment

Question

I'm trying implement a TabHost FragmentActivity, but when i run the app occurs ClassCastException: cannot be cast to android.support.v4.app.Fragment.

My project have the supportev4 library configurated, but not work.

My Activity extend from FragmentActivity, but not work.

What this problem?

package br.com.teste.activity;

import java.util.HashMap;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TabHost;
import android.widget.TabHost.TabContentFactory;
import android.widget.TabHost.TabSpec;
import br.com.teste.R;


public class MainFragmentActivity extends FragmentActivity implements TabHost.OnTabChangeListener {

private TabHost mTabHost;
private HashMap<String, TabInfo> mapTabInfo = new HashMap<String, TabInfo>();
private TabInfo mLastTab = null;


private class TabInfo {
    private String tag;
    private Class clss;
    private Bundle args;
    private Fragment fragment;

    TabInfo(String tag, Class clazz, Bundle args) {
        this.tag = tag;
        this.clss = clazz;
        this.args = args;
    }
}

class TabFactory implements TabContentFactory {

    private final Context mContext;

    /**
     * 
     * @param context
     */

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

    /**
     * (non-Javadoc)
     * 
     * @see android.widget.TabHost.TabContentFactory#createTabContent(java.lang.String)
     */

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


@Override
protected void onCreate(Bundle savedInstance)
{
    super.onCreate(savedInstance);
    setContentView(R.layout.maintabhost);

    initializeTabHost(savedInstance);

    if(savedInstance != null)
        mTabHost.setCurrentTabByTag(savedInstance.getString("tab"));

}

@Override
protected void onSaveInstanceState(Bundle outState)
{
    outState.putString("tab", mTabHost.getCurrentTabTag()); 
    super.onSaveInstanceState(outState);
}

/**
 * Inicializa as tabs
 * @param args
 */
private void initializeTabHost(Bundle args)
{
    mTabHost = (TabHost)findViewById(android.R.id.tabhost);
    mTabHost.setup();
    TabInfo tabInfo = null;
    String tagTabDefaul = "pesquisar";
    String tagTab;
    TabSpec tabSpecLocal = null;

    //Add tab1
    tagTab = "pesquisar";
    tabSpecLocal = this.mTabHost.newTabSpec(tagTab);
    View viewPesquisa = LayoutInflater.from(this).inflate(
            R.layout.tab_layout_view, null);
    LinearLayout lPesquisa = (LinearLayout)viewPesquisa.findViewById(R.id.tabsLayout);

        lPesquisa.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_pesquisa_background_selector));


    tabSpecLocal.setIndicator(viewPesquisa);
    tabInfo = new TabInfo(tagTab, MainActivity.class, args);
    this.mapTabInfo.put(tabInfo.tag, tabInfo);
    addTab(this, this.mTabHost, tabSpecLocal, tabInfo);

    tagTab = "lines";
    tabSpecLocal = this.mTabHost.newTabSpec(tagTab);
    View viewLines = LayoutInflater.from(this).inflate(
            R.layout.tab_layout_view, null);
    LinearLayout lLines = (LinearLayout)viewLines.findViewById(R.id.tabsLayout);
        lLinhas.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_lines_background_selector));



    tabSpecLocal.setIndicator(viewLines);
    tabInfo = new TabInfo(tagTab, ListLinesActivity.class, args);
    this.mapTabInfo.put(tabInfo.tag, tabInfo);
    addTab(this, this.mTabHost, tabSpecLocal, tabInfo);

    //Adiciona tab de Fields
    tagTab = "fields";
    tabSpecLocal = this.mTabHost.newTabSpec(tagTab);
    View viewFields = LayoutInflater.from(this).inflate(
            R.layout.tab_layout_view, null);
    LinearLayout lFields = (LinearLayout)viewFields.findViewById(R.id.tabsLayout);

        lFields.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_fields_background_selector));


    tabSpecLocal.setIndicator(viewFields);
    tabInfo = new TabInfo(tagTab, ListFieldsActivity.class, args);
    this.mapTabInfo.put(tabInfo.tag, tabInfo);
    addTab(this, this.mTabHost, tabSpecLocal, tabInfo);

    //Seta a tab default
    this.onTabChanged(tagTabDefaul);

    mTabHost.setOnTabChangedListener(this);
}

/**
 * Adiciona as tab's
 * @param activity
 * @param tabHost
 * @param tabSpec
 * @param tabInfo
 */
private static void addTab(MainFragmentActivity activity, TabHost tabHost, TabSpec tabSpec, TabInfo tabInfo)
{
    //Attach a tab view factory to ths spec     
    tabSpec.setContent(activity.new TabFactory(activity));
    String tag = tabSpec.getTag();

    //Verifica se já existe um fragmento para esta tab, provavelmente de uma ação anterior
    //Se tiver, desativa o fragmento, porque seu estado inicial é para não apresentar
    tabInfo.fragment = activity.getSupportFragmentManager().findFragmentByTag(tag);
    if((tabInfo.fragment != null) && (tabInfo.fragment.isDetached()))
    {
        FragmentTransaction ft = activity.getSupportFragmentManager().beginTransaction();
        ft.detach(tabInfo.fragment);
        ft.commit();
        activity.getSupportFragmentManager().executePendingTransactions();
    }
    tabHost.addTab(tabSpec);
}


public void onTabChanged(String tag)
{
    TabInfo newTab = this.mapTabInfo.get(tag);
    if(mLastTab != newTab)
    {
        FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();
        if(mLastTab != null)
        {
            if(mLastTab.fragment != null)
            {
                ft.detach(mLastTab.fragment);
            }
        }
        if(newTab != null)
        {
            if(newTab.fragment == null)
            {
                newTab.fragment = Fragment.instantiate(this, newTab.clss.getName(), newTab.args);
                ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
            }
            else
            {
                ft.attach(newTab.fragment);
            }
        }
        mLastTab = newTab;
        ft.commit();
        this.getSupportFragmentManager().executePendingTransactions();
    }
}


//Cria a tab com personalização de layout
/*
private static View createTabView(final Context context, final String text) {
    View view = LayoutInflater.from(context).inflate(
            R.layout.tab_layout_view, null);
    TextView tv = (TextView) view.findViewById(R.id.tabsText);
    tv.setText(text);
    return view;
}
*/
}

UPDATED

My logCat

09-05 01:57:07.655: D/dalvikvm(727): GC_CONCURRENT freed 347K, 5% free 9061K/9479K, paused 91ms+6ms, total 192ms
09-05 01:57:07.655: D/dalvikvm(727): WAIT_FOR_CONCURRENT_GC blocked 56ms
09-05 01:57:07.695: D/AndroidRuntime(727): Shutting down VM
09-05 01:57:07.705: W/dalvikvm(727): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-05 01:57:07.745: E/AndroidRuntime(727): FATAL EXCEPTION: main
09-05 01:57:07.745: E/AndroidRuntime(727): java.lang.RuntimeException: Unable to start activity ComponentInfo{br.com.teste/br.com.teste.activity.MainFragmentActivity}: java.lang.ClassCastException: br.com.teste.activity.MainActivity cannot be cast to android.support.v4.app.Fragment
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.os.Looper.loop(Looper.java:137)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread.main(ActivityThread.java:4745)
09-05 01:57:07.745: E/AndroidRuntime(727):  at java.lang.reflect.Method.invokeNative(Native Method)
09-05 01:57:07.745: E/AndroidRuntime(727):  at java.lang.reflect.Method.invoke(Method.java:511)
09-05 01:57:07.745: E/AndroidRuntime(727):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-05 01:57:07.745: E/AndroidRuntime(727):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-05 01:57:07.745: E/AndroidRuntime(727):  at dalvik.system.NativeStart.main(Native Method)
09-05 01:57:07.745: E/AndroidRuntime(727): Caused by: java.lang.ClassCastException: br.com.teste.activity.MainActivity cannot be cast to android.support.v4.app.Fragment
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.support.v4.app.Fragment.instantiate(Fragment.java:402)
09-05 01:57:07.745: E/AndroidRuntime(727):  at br.com.teste.activity.MainFragmentActivity.onTabChanged(MainFragmentActivity.java:208)
09-05 01:57:07.745: E/AndroidRuntime(727):  at br.com.teste.activity.MainFragmentActivity.initializeTabHost(MainFragmentActivity.java:159)
09-05 01:57:07.745: E/AndroidRuntime(727):  at br.com.teste.activity.MainFragmentActivity.onCreate(MainFragmentActivity.java:75)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.Activity.performCreate(Activity.java:5008)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-05 01:57:07.745: E/AndroidRuntime(727):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-05 01:57:07.745: E/AndroidRuntime(727):  ... 11 more

Post your logcat please. Also, ClassCastExceptions that don't make sense can often be fixed by cleaning your project. "Project --> Clean..." in Eclipse — codeMagic
– codeMagic, Commented Sep 5, 2013 at 0:39
Which line is your error coming from? It looks like you may be passing a MainFragmentActivity object to a constructor that requires a Context object, but that shouldn't cause an error for a Fragment. — Jon
– Jon, Commented Sep 5, 2013 at 0:48
coddeMagic, I tried it, but not work. Jon, I'm updated with logCat. Thanks for your help. — user1352652
– user1352652, Commented Sep 5, 2013 at 2:03
I added an example that I believe should work for you, but you may run into some other issues depending on the class it gets. — Jon
– Jon, Commented Sep 5, 2013 at 3:17
Disregard my previous comment, I added a quick check with instanceof which should catch any bad classes that get passed to it. Fragment.class.isInstance(newTab.clss) would also give the same results as instanceof, but is slightly less efficient. — Jon
– Jon, Commented Sep 5, 2013 at 4:04

Jon · Accepted Answer · 2013-09-05 04:24:39Z

1

In your initializeTabHost(Bundle) method you are creating a new TabInfo object with the MainActivity Class and then Instantiating a Fragment using that same class in your onTabChanged(String) method. You'll need to have MainActivity extend Fragment and then instantiate newTab.clss and cast it to a Fragment.

Edit: added verification of Class type

public void onTabChanged(String tag)
{
    TabInfo newTab = this.mapTabInfo.get(tag);
    if(mLastTab != newTab)
    {
        FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();
        if(mLastTab != null)
        {
            if(mLastTab.fragment != null)
            {
                ft.detach(mLastTab.fragment);
            }
        }
        if(newTab != null)
        {
            if(newTab.fragment == null)
            {
                Object objFragment = null;
                try {
                    objFragment = Class.forName(newTab.clss.getName()).newInstance();
                } catch (InstantiationException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
                if (! (objFragment instanceof Fragment))
                {
                    Log.e("MainFragmentActivity", "Unable to cast " + newTab.clss.toString() + " to Fragment!");
                    return;
                }
                newTab.fragment = (Fragment) objFragment;
                newTab.fragment.setArguments(newTab.args);
                ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
            }
            else
            {
                ft.attach(newTab.fragment);
            }
        }
        mLastTab = newTab;
        ft.commit();
        this.getSupportFragmentManager().executePendingTransactions();
    }
}

edited Sep 5, 2013 at 4:24

answered Sep 5, 2013 at 2:56

Jon

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2 Comments

Jon Over a year ago

Sorry, I just just noticed I had newTab.clss.toString() instead of newTab.clss.getName(). It should work much better now :)

user1352652 Over a year ago

Jon, Thanks for your help, really the MainActivity class is a Activity and not a fragment. I'm migrating my project to fragment actvitys and some classes extends from Activity yet. In this case, all classes informed in tabinfos are Activitys (MainActivity, ListLinesActivity and ListFieldsActivits), but in my testes I changed all tabinfos to use MainFragmentActivity (just to see if would work) and the error continue. I will try remove tabinfos and execute again to see what's happen (Later, when I'm at home and can work on the project). Any other suggestions?

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