空指针在片段内创建片段时出现异常

Question

我在片段内创建片段，但我得到了NullPointerException。我不知道为什么相同的代码在扩展FragmentActivity的类中工作，但它在扩展Fragment的类中不起作用。以下是我的代码，

public class SecondLevel extends Fragment implements OnClickListener { 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     Button btn1, btn2, btn3, btn4; 
     View view = inflater.inflate(R.layout.secondlevel, container, false); 

     btn1 = (Button) view.findViewById(R.id.button11); 
     btn1.setOnClickListener(this); 

    ... 
    ... 
    ... 
     return view; 
    } 

    @Override 
    public void onClick(View view) { 
     Fragment fr1 = null; 
     switch (view.getId()) { 
     case R.id.button11: 
      Toast.makeText(this.getActivity(), "Button 1 is clicked!", 
        Toast.LENGTH_LONG).show(); 
      fr1 = new ThirdFragment(); 
      FragmentManager fm1 = getSupportFragmentManager(); 
      FragmentTransaction fragmentTransaction = fm1.beginTransaction(); 
      fragmentTransaction.replace(R.id.fragment_place, fr1); 
      fragmentTransaction.commit(); 
      ..... 

现在在ThirdFragment我在做什么如下：

package com.javacodegeeks.android.fragmentstest; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 

public class ThirdFragment extends Fragment { 
@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) { 
    Log.e("F1", "F1"); 

    // Inflate the layout for this fragment 

    return inflater.inflate(R.layout.thirdlevel, container, false); 
} 
} 

请注意，我已经进口的相同的支持库，所以它不是这个问题。

它我的XML第三层子：

<Button 
    android:id="@+id/buttonlevel3" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Button" /> 

</LinearLayout> 

它我的第二级别的xml：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:id="@+id/laSecond" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:orientation="vertical" > 

<TextView 
    android:id="@+id/textView1" 
    android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
    android:text="Level 1" /> 

<Button 
    android:id="@+id/button11" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Button 1" /> 

<TextView 
    android:id="@+id/textView2" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Level 2" /> 

<Button 
    android:id="@+id/button22" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Button 2" /> 

<TextView 
    android:id="@+id/textView33" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Level 3" /> 

<Button 
    android:id="@+id/button33" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Button 3" /> 

<TextView 
    android:id="@+id/textView44" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Level 4" /> 

    <Button 
    android:id="@+id/button44" 
     android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Button 4" /> 

    </LinearLayout> 

logcat的：

E/AndroidRuntime(19842): FATAL EXCEPTION: main 
03-07 10:58:09.138: E/AndroidRuntime(19842): java.lang.NullPointerException 
03-07 10:58:09.138: E/AndroidRuntime(19842):at com.javacodegeeks.android.fragmentstest.SecondLevel.onClick(SecondLevel.java:50) 
03-07 10:58:09.138: E/AndroidRuntime(19842): at android.view.View.performClick(View.java:3549) 
E/AndroidRuntime(19842): at android.view.View$PerformClick.run(View.java:14393) 
E/AndroidRuntime(19842):at android.os.Handler.handleCallback(Handler.java:605) 
E/AndroidRuntime(19842):at android.os.Handler.dispatchMessage(Handler.java:92) 

Answer 1

改变这种从

FragmentManager fm1 = getSupportFragmentManager(); 

到

FragmentManager fm1 = getFragmentManager();