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我在列表视图中的 setAdapter 处收到 NullPointerException。如果有人可以帮助我，我将不胜感激。我的文件如下：

MainActivity.java

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

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the app.
    mSectionsPagerAdapter = new SectionsPagerAdapter(
            getSupportFragmentManager());

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

    MainActivityContext=this;

    callGeolocationApi1();
    ListView categoryList = (ListView) this.findViewById(R.id.listView);

    CategoryAdapter categoryAdapter = new CategoryAdapter(this, R.layout.category2_row_layout,
            getCategoriesList());

    //java.lang.NullPointerException occurs here
            categoryList.setAdapter(categoryAdapter);

}
private List<String> getCategoriesList() {
    List<String> strlist = new ArrayList<String>();
    strlist.add("str1");
    strlist.add("str2");
    return strlist;
}

fragment_main_dummy.xml

    <?xml version="1.0" encoding="utf-8"?>                                        <LinearLayout
    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:orientation="vertical"
    android:background="@color/orange" tools:context=".MainActivity">
<ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/listView"
        android:layout_gravity="center"
        tools:listitem="@layout/category2_row_layout"/>

category2_row_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:padding="6dip"
  android:background="#00000000"> 
<TextView  
  android:id="@+id/category_name"
  android:layout_width="200dip" 
  android:layout_height="wrap_content" 
  android:textSize="20sp"
  android:layout_marginTop="10dip"
  android:scrollbars="vertical"
  android:fadingEdge="vertical"
  android:layout_alignParentLeft="true"
  android:background="#00000000"
/>
<ImageButton
  android:id="@+id/category_delete_button"
  android:background="#00000000"
  android:src="@drawable/settings"
  android:layout_width="50dip"
  android:layout_height="50dip"
  android:scrollbars="vertical"
  android:fadingEdge="vertical"
  android:layout_alignParentRight="true"
  android:focusable="false"
  android:focusableInTouchMode="false"
/> 
</RelativeLayout>

Logcat - http://pastebin.com/phLYcPC8

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