Question

I have this layout, containing a single TextView, but I would like to be able to change it’s content (the text to be visualized) in a dynamic way, using java code.

<LinearLayout

    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

     <TextView 

        android:id="@+id/list_header"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:gravity="center_vertical"
        android:layout_alignParentTop="true"
        android:layout_alignParentBottom="true"
        android:textStyle="bold"
        android:textSize="22dp"
        android:textColor="#FFFFFF"
        android:padding="10dp"
        android:background="#336699" 

     />

</LinearLayout>

As you can see I have not defined the android:text="blablabla" cause it is not fixed at the point of the code in which I use it.

I would like some method such as:

TextView headerValue = (TextView) findViewById(R.id.list_header);
headerValue.setText( "blablabla" );

but this won’t work because I use this layout for defining the style of a header of the list, and these lines conflict with the following I need to use:

View header = (View)getLayoutInflater().inflate(R.layout.list_header_layout, null);
listView.addHeaderView(header);

Can you please help me fix this problem?

---

LOGCAT:

E/AndroidRuntime( 1468):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.access$600(ActivityThread.java:123)
E/AndroidRuntime( 1468):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
E/AndroidRuntime( 1468):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 1468):    at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.main(ActivityThread.java:4424)
E/AndroidRuntime( 1468):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 1468):    at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime( 1468):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
E/AndroidRuntime( 1468):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
E/AndroidRuntime( 1468):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 1468): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.DVA_HLUI/com.DVA_HLUI.DVA_HLUISuperviseActivity}: java.lang.NullPointerException
E/AndroidRuntime( 1468):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.startActivityNow(ActivityThread.java:1797)
E/AndroidRuntime( 1468):    at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135)
E/AndroidRuntime( 1468):    at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347)
E/AndroidRuntime( 1468):    at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:682)
E/AndroidRuntime( 1468):    at android.widget.TabHost.setCurrentTab(TabHost.java:346)
E/AndroidRuntime( 1468):    at android.widget.TabHost.addTab(TabHost.java:236)
E/AndroidRuntime( 1468):    at com.DVA_HLUI.DVA_HLUIActivity.onCreate(DVA_HLUIActivity.java:41)
E/AndroidRuntime( 1468):    at android.app.Activity.performCreate(Activity.java:4465)
E/AndroidRuntime( 1468):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
E/AndroidRuntime( 1468):    ... 11 more
E/AndroidRuntime( 1468): Caused by: java.lang.NullPointerException
E/AndroidRuntime( 1468):    at com.DVA_HLUI.DVA_HLUISuperviseActivity.onCreate(DVA_HLUISuperviseActivity.java:41)
E/AndroidRuntime( 1468):    at android.app.Activity.performCreate(Activity.java:4465)
E/AndroidRuntime( 1468):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
E/AndroidRuntime( 1468):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
E/AndroidRuntime( 1468):    ... 21 more

---

Activity Class:

public class MyActivity extends ListActivity 
{

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    { 

        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_activity);

        ListView listView = (ListView) findViewById(android.R.id.list);

        listEntryClass listEntries[] = new listEntryClass[]
        {
            new listEntryClass( "bla", "bla"),
            new listEntryClass( "bla", "bla" )
        };

        listEntryArrayAdapter adapter = new listEntryArrayAdapter(this, R.layout.list_entry_layout, listEntries);

        TextView headerValue = (TextView) findViewById(R.id.list_header);
        headerValue.setText( this.getString(R.string.headerSupervise) );

        View header = (View)getLayoutInflater().inflate(R.layout.list_header_layout, null);
        listView.addHeaderView(header);
        listView.setAdapter(adapter);
}

Answer 1

TextView headerValue = (TextView) header.findViewById(R.id.list_header);

Should be referenced from header view.

So Change your code to follwing.

    View header = (View)getLayoutInflater().inflate(R.layout.list_header_layout, null);
    TextView headerValue = (TextView) header.findViewById(R.id.list_header);
    headerValue.setText( this.getString(R.string.headerSupervise) );

    listView.addHeaderView(header);
    listView.setAdapter(adapter);