Problem mit android.support.v7.app.ActionBarActivity

Question

Ich habe ein Problem beim Kompilieren meines Codes, um ehrlich zu sein, ich bin mir nicht sicher, was hier falsch läuft. Ich verwende ein Tutorial, das ich online gefunden habe, um zu erfahren, wie man eine Android Chat App erstellt. Ich habe keine roten Linien?

Hier ist mein Code für die MainActivity:

package com.example.brian.chatapp; 

import android.support.design.widget.TabLayout; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.support.v4.view.ViewPager; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 

import android.widget.TextView; 

import com.example.brian.fragments.Chats; 

import java.util.Locale; 

public class MainActivity extends AppCompatActivity { 

/** 
* The {@link android.support.v4.view.PagerAdapter} that will provide 
* fragments for each of the sections. We use a 
* {@link FragmentPagerAdapter} derivative, which will keep every 
* loaded fragment in memory. If this becomes too memory intensive, it 
* may be best to switch to a 
* {@link android.support.v4.app.FragmentStatePagerAdapter}. 
*/ 
private SectionsPagerAdapter mSectionsPagerAdapter; 

/** 
* The {@link ViewPager} that will host the section contents. 
*/ 
private ViewPager mViewPager; 

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 
    // Create the adapter that will return a fragment for each of the three 
    // primary sections of the activity. 
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager()); 

    // Set up the ViewPager with the sections adapter. 
    mViewPager = (ViewPager) findViewById(R.id.container); 
    mViewPager.setAdapter(mSectionsPagerAdapter); 

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs); 
    tabLayout.setupWithViewPager(mViewPager); 

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
    fab.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
        .setAction("Action", null).show(); 
     } 
    }); 

} 


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

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 

    //noinspection SimplifiableIfStatement 
    if (id == R.id.action_settings) { 
     return true; 
    } 

    return super.onOptionsItemSelected(item); 
} 




/** 
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to 
* one of the sections/tabs/pages. 
*/ 
public class SectionsPagerAdapter extends FragmentPagerAdapter {public SectionsPagerAdapter(FragmentManager fm) { 
    super(fm); 
}@Override 
public Fragment getItem(int position) { 
    if (position == 1) { 
     return new Chats(); 
    } else 
     return PlaceholderFragment.newInstance(position + 1); 
}@Override 
public int getCount() { 
// Show 3 total pages. 
    return 3; 
}@Override 
public CharSequence getPageTitle(int position) { 
    Locale l = Locale.getDefault(); 
    switch (position) { 
     case 0: 
      return getString(R.string.title_section1).toUpperCase(l); 
     case 1: 
      return getString(R.string.title_section2).toUpperCase(l); 
     case 2: 
      return getString(R.string.title_section3).toUpperCase(l); 
    } 
    return null; 
} 
} 

/** 
* A placeholder fragment containing a simple view. 
*/ 
public static class PlaceholderFragment extends Fragment { 
    /** 
    * The fragment argument representing the section number for this 
    * fragment. 
    */ 
    private static final String ARG_SECTION_NUMBER = "section_number"; 

    /** 
    * Returns a new instance of this fragment for the given section 
    * number. 
    */ 
    public static PlaceholderFragment newInstance(int sectionNumber) { 
     PlaceholderFragment fragment = new PlaceholderFragment(); 
     Bundle args = new Bundle(); 
     args.putInt(ARG_SECTION_NUMBER, sectionNumber); 
     fragment.setArguments(args); 
     return fragment; 
    } 

    public PlaceholderFragment() { 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.fragment_main, container, false); 
     TextView textView = (TextView) rootView.findViewById(R.id.section_label); 
     textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER))); 
     return rootView; 
    } 
} 
} 

Hier ist der Code für die Chats Aktivität:

package com.example.brian.fragments; 

import java.util.ArrayList; 
import java.util.Random; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v7.app.ActionBarActivity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.ViewGroup; 
import android.widget.EditText; 
import android.widget.ImageButton; 
import android.widget.ListView; 

import com.example.brian.chatapp.ChatAdapter; 
import com.example.brian.chatapp.ChatMessage; 
import com.example.brian.chatapp.CommonMethods; 
import com.example.brian.chatapp.R; 

public class Chats extends Fragment implements OnClickListener { 

private EditText msg_edittext; 
private String user1 = "khushi", user2 = "khushi1"; 
private Random random; 
public static ArrayList<ChatMessage> chatlist; 
public static ChatAdapter chatAdapter; 
ListView msgListView; 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.chat_layout, container, false); 
    random = new Random(); 
    ((ActionBarActivity) getActivity()).getSupportActionBar().setTitle(
      "Chats"); 
    msg_edittext = (EditText) view.findViewById(R.id.messageEditText); 
    msgListView = (ListView) view.findViewById(R.id.msgListView); 
    ImageButton sendButton = (ImageButton) view 
      .findViewById(R.id.sendMessageButton); 
    sendButton.setOnClickListener(this); 

    // ----Set autoscroll of listview when a new message arrives----// 
    msgListView.setTranscriptMode(ListView.TRANSCRIPT_MODE_ALWAYS_SCROLL); 
    msgListView.setStackFromBottom(true); 

    chatlist = new ArrayList<ChatMessage>(); 
    chatAdapter = new ChatAdapter(getActivity(), chatlist); 
    msgListView.setAdapter(chatAdapter); 
    return view; 
} 

@Override 
public void onSaveInstanceState(Bundle outState) { 
} 

public void sendTextMessage(View v) { 
    String message = msg_edittext.getEditableText().toString(); 
    if (!message.equalsIgnoreCase("")) { 
     final ChatMessage chatMessage = new ChatMessage(user1, user2, 
       message, "" + random.nextInt(1000), true); 
     chatMessage.setMsgID(); 
     chatMessage.body = message; 
     chatMessage.Date = CommonMethods.getCurrentDate(); 
     chatMessage.Time = CommonMethods.getCurrentTime(); 
     msg_edittext.setText(""); 
     chatAdapter.add(chatMessage); 
     chatAdapter.notifyDataSetChanged(); 
    } 
} 

@Override 
public void onClick(View v) { 
    switch (v.getId()) { 
     case R.id.sendMessageButton: 
      sendTextMessage(v); 

    } 
} 

} 

Dies ist der Fehler, dass ich erhalte:

07-21 04:43:39.605 3063-3063/com.example.brian.chatapp E/AndroidRuntime: FATAL EXCEPTION: main 
                       Process: com.example.brian.chatapp, PID: 3063 
                    java.lang.ClassCastException: com.example.brian.chatapp.MainActivity cannot be cast to android.support.v7.app.ActionBarActivity 
                     at com.example.brian.fragments.Chats.onCreateView(Chats.java:35) 
                     at android.support.v4.app.Fragment.performCreateView(Fragment.java:2074) 
                     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104) 
                     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1286) 
                     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:758) 
                     at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1632) 
                     at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:637) 
                     at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143) 
                     at android.support.v4.view.ViewPager.populate(ViewPager.java:1235) 
                     at android.support.v4.view.ViewPager.populate(ViewPager.java:1083) 
                     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1609) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:669) 
                     at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:89) 
                     at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1319) 
                     at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:734) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
                     at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
                     at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
                     at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
                     at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
                     at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
                     at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
                     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560) 
                     at android.view.View.measure(View.java:17430) 
                     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001) 
                     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166) 
                     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372) 
                     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054) 
                     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779) 
                     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) 
                     at android.view.Choreographer.doCallbacks(Choreographer.java:580) 
                     at android.view.Choreographer.doFrame(Choreographer.java:550) 
                     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) 
                     at android.os.Handler.handleCallback(Handler.java:739) 
                     at android.os.Handler.dispatchMessage(Handler.java:95) 
                     at android.os.Looper.loop(Looper.java:135) 
                     at android.app.ActivityThread.main(ActivityThread.java:5221) 
                     at java.lang.reflect.Method.invoke(Native Method) 
                     at java.lang.reflect.Method.invoke(Method.java:372) 
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller 

Hier ist ein Link zum Tutorial als Referenz: Chat App Tutorial

Answer 1

Im onCreateView des Fragments, wenn Sie versuchen, den Titel ActionBar zu ändern, indem Sie Ihre Mutter Aktivität Gießen Sie tat:

((ActionBarActivity) getActivity()).getSupportActionBar().setTitle("Chats"); 

Während Ihrer Eltern Aktivität von AppCompatActivity erweitert wird und nicht ActionBarActivity. Sie sollten es so Stimmen:

((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Chats");