Question

I am building and android app and have created the login screen. The next screen will show the logged in user a set of options from which he has to choose one.

The second activity is started from the onPostExecute method of an AsyncTask using the startActivity(intent) code.

Intent intent = null;
intent = new Intent(context, DisplayMessageActivity.class);
    context.startActivity(intent);      

I am trying to build the UI for this screen using the .xml file activity_display_message.xml. The entry for this has been made to the manifest file.
Any of the layout attributes that I am specifying in this .xml file are not getting applied. Any help in this regard is highly appreciated. For example using the code below I am unable to get the background color that I have set. This works fine with the .xml that I have for my main activity.

The onCreate function for my DisplayMessageActivity class is

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display_message);

    Intent intent = getIntent();
    String message = intent.getStringExtra(CommonStaticValues.EXTRA_MESSAGE);

    TextView textView = new TextView(this);
    textView.setTextSize(40);
    textView.setText(message);

    setContentView(textView);
}

The complete activity_display_message.xml file is

<RelativeLayout 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:background="@color/background_color">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="@string/hello_world"
    tools:context=".DisplayMessageActivity" />

</RelativeLayout>

Answer 1

I see two problems here that are probably causing your problem. You first use setContentView like this:

setContentView(R.layout.activity_display_message);

That applied your XML file to the Activity, which is want you want. Later, you call it again with a TextView you created locally. If you wanted an Activity that consisted of one TextView on the screen, that’s one way to do it, but you don’t need it here because you have an XML definition of the Activity already.

Secondly, your XML file’s TextView has no android:id. That’s used to reference the TextView from the code. So, modify your XML’s TextView to add that like this:

<TextView
android:id="@+id/txtView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="@string/hello_world"
tools:context=".DisplayMessageActivity" />

Then, back in your onCreate, instead of constructing a new TextView with TextView textView = new TextView(this);, access the TextView from the XML you applied like this:

TextView textView = (TextView) findViewById(R.id.txtView);

Notice that the argument for findViewById is the id you create in the XML.