why is there content_main.xml and activity_main.xml by default instead of just activity_main.xml?

Question

I have just begun learning Android App development. I have Android Studio 1.4. In my layout folder I have two XML files (content_main.xml and activity_mai

Answer 1

According to new design pattern in android studio activity_main.xml will determine how the look of the main activity should be. And on the other hand content_main.xml will determine the contents in the activity_main.xml. That is content_main.xml will contain the textview, edittext, button etc component. And the content_main.xml will be included by the activity_main.xml .

So we can think of content_main.xml just like partial in HTML. activity_main.xml will contain your activity global design, and content_main.xml the contents.

What is the role of content_main.xml in android studio 1.4?

So it seems the content_main.xml is a part of a new design pattern introduced in Android Studio 1.4. For the moment, to get along with the tutorials you can find pick the 'empty activity' when creating a new project. It will not contain the content_main.xml.

As mentioned before, the layout file used for your activity is set with setContentView(R.layout.activity_main); in the onCreate function of the activity.

public class MainActivity extends AppCompatActivity {

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