Question

I customized a header view in a ListView by using xml file, this file is:

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView 
        android:id="@id/post_title_tv" 
        android:paddingLeft="8.0dip" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="Post title" 
        android:layout_alignParentLeft="true" />
    <ImageView 
        android:id="@id/post_fave_image" 
        android:paddingLeft="10.0dip" 
        android:paddingRight="8.0dip" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:visibility="gone"
        android:src="@drawable/btn_star_big_on" 
        android:layout_alignParentRight="true" />
</RelativeLayout>

then, I add it in my Listview by this code:

LayoutInflater layoutInflater = (LayoutInflater)this.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
        RelativeLayout headerLayout = (RelativeLayout)layoutInflater.inflate( R.layout.post_titl, null, false );

        postTitle = (TextView) findViewById(R.id.post_title_tv);
        postTitle.setText(postName);

then , when I run it, I get this error:

  03-04 14:52:41.946: E/AndroidRuntime(484): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.google.client.ui/com.google.client.ui.PostListView}: java.lang.NullPointerException
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.os.Looper.loop(Looper.java:123)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-04 14:52:41.946: E/AndroidRuntime(484):  at java.lang.reflect.Method.invokeNative(Native Method)
03-04 14:52:41.946: E/AndroidRuntime(484):  at java.lang.reflect.Method.invoke(Method.java:507)
03-04 14:52:41.946: E/AndroidRuntime(484):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-04 14:52:41.946: E/AndroidRuntime(484):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-04 14:52:41.946: E/AndroidRuntime(484):  at dalvik.system.NativeStart.main(Native Method)
03-04 14:52:41.946: E/AndroidRuntime(484): Caused by: java.lang.NullPointerException
03-04 14:52:41.946: E/AndroidRuntime(484):  at com.google.client.ui.PostListView.setComponent(PostListView.java:105)
03-04 14:52:41.946: E/AndroidRuntime(484):  at com.google.client.ui.PostListView.onCreate(PostListView.java:53)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-04 14:52:41.946: E/AndroidRuntime(484):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)

this is a NullPointerException, I can’t get the TextView resource in post_title.xml. The question is:
why can’t I get the TextView resource?

Answer 1

postTitle = (TextView)headerLayout.findViewById(R.id.post_title_tv);