Question

I am getting the java.lang.NullPointerException on createTabContent for the following code. There are two tabspecs. When I called and set the tab , changed the tabs for the first time it is ok. But when i called again while I am on the second tab, its hit the null pointer exception for line : NoStudentText.setVisibility(View.VISIBLE);

I will show No Student Text if there is no data for the student list. It shows the text for the first time call. But If I do second time call to that tab, got the error.

tspecStudent.setContent(new TabContentFactory() {
            public View createTabContent(String arg0) {
                if(listStudent != null && listStudent .size() > 0) {
                    //show the student list
                } else {
                    TextView noStudentText = (TextView)findViewById(R.id.NoStudentText);
                    noStudentText.setVisibility(View.VISIBLE);
                    return noStudentText;
                }

            }
        });

I am including another xml to the main layout.

main.xml

<TabHost
        android:id="@+id/tabhostMain"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1" > 
....
<include layout="@layout/tab_student" />

</TabHost>

tab_student.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabcontent"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

 <ListView
        android:id="@+id/StudentList"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:drawSelectorOnTop="false" />

<TextView
        android:id="@+id/NoStudentText"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="No Student"
        android:visibility="gone" />

</FrameLayout>

Answer 1

Some times because of yours applied condition it couldn’t able to initialize so,
Make this variable as global like–

    TextView _noStudentText;

Initialize it in onCreate method::

   _noStudentText = (TextView)findViewById(R.id.NoStudentText);

Now change the visibility according to your need like this–

    _noStudentText.setVisibility(View.VISIBLE);