Linear Layout

LinearLayout is a ViewGroup that displays child View elements in a linear direction, either vertically or horizontally.

You should be careful about over-using the LinearLayout. If you begin nesting multiple LinearLayouts, you may want to consider using a RelativeLayout instead.

1. Start a new project named HelloLinearLayout.
2. Open the res/layout/main.xml file and insert the following:

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:orientation="vertical"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent">
     <LinearLayout
         android:orientation="horizontal"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:layout_weight="1">
         <TextView
             android:text="red"
             android:gravity="center_horizontal"
             android:background="#aa0000"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:layout_weight="1"/>
         <TextView
             android:text="green"
             android:gravity="center_horizontal"
             android:background="#00aa00"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:layout_weight="1"/>
         <TextView
             android:text="blue"
             android:gravity="center_horizontal"
             android:background="#0000aa"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:layout_weight="1"/>
         <TextView
             android:text="yellow"
             android:gravity="center_horizontal"
             android:background="#aaaa00"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:layout_weight="1"/>
     </LinearLayout>
     <LinearLayout
       android:orientation="vertical"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent"
       android:layout_weight="1">
       <TextView
           android:text="row one"
           android:textSize="15pt"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_weight="1"/>
       <TextView
           android:text="row two"
           android:textSize="15pt"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_weight="1"/>
       <TextView
           android:text="row three"
           android:textSize="15pt"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_weight="1"/>
       <TextView
           android:text="row four"
           android:textSize="15pt"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_weight="1"/>
     </LinearLayout>
   </LinearLayout>
   

   Carefully inspect this XML. There is a root LinearLayout that defines its orientation to be vertical—all child Views (of which it has two) will be stacked vertically. The first child is another LinearLayout that uses a horizontal orientation and the second child is a LinearLayout that uses a vertical orientation. Each of these nested LinearLayouts contain several TextView elements, which are oriented with each other in the manner defined by their parent LinearLayout.

3. Now open HelloLinearLayout.java and be sure it loads the res/layout/main.xml layout in the onCreate() method:

   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
   }
   

   The setContentView(int) method loads the layout file for the Activity, specified by the resource ID — R.layout.main refers to the res/layout/main.xml layout file.

4. Run the application.

You should see the following:

Notice how the XML attributes define each View's behavior. Try experimenting with different values for android:layout_weight to see how the screen real estate is distributed based on the weight of each element. See the Common Layout Objects document for more about how LinearLayout handles the android:layout_weight attribute.

References

• LinearLayout
• TextView