Android Linear Layout

Advertisements


Android LinearLayout is a view group that aligns all children in a single direction, vertically or horizontally.

LinearLayout Attributes

Following are the important attributes specific to LinearLayout:

AttributeDescription
android:idThis is the ID which uniquely identifies the layout.
android:baselineAlignedThis must be a boolean value, either "true" or "false" and prevents the layout from aligning its children's baselines.
android:dividerThis is drawable to use as a vertical divider between buttons. You use a color value, in the form of "#rgb", "#argb", "#rrggbb", or "#aarrggbb".
android:gravityThis specifies how an object should position its content, on both the X and Y axes. Possible values are top, bottom, left, right, center, center_vertical, center_horizontal etc.
android:orientationThis specifies the direction of arrangmet and you will use "horizontal" for a row, "vertical" for a column. The default is horizontal.

Example

This example will take you through simple steps to show how to create your own Android application using Linear Layout. Follow the following steps to modify the Android application we created in Hello World Example chapter:

StepDescription
1You will use Eclipse IDE to create an Android application and name it as HelloWorld under a package com.example.helloworld as explained in the Hello World Example chapter.
2Modify the detault content of res/layout/activity_main.xml file to include few buttons in linear layout.
3Define required constants start_service, pause_service and stop_service in res/values/strings.xml file
4Run the application to launch Android emulator and verify the result of the changes done in the aplication.

Following is the content of the modified main activity file src/com.example.helloworld/MainActivity.java. This file can include each of the fundamental lifecycle methods.

package com.example.helloworld;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    
}

Following will be the content of res/layout/activity_main.xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:orientation="vertical" >

   <Button android:id="@+id/btnStartService"
   android:layout_width="150px"
   android:layout_height="wrap_content"
   android:text="@string/start_service"
   
   <Button android:id="@+id/btnPauseService"
   android:layout_width="150px"
   android:layout_height="wrap_content"
   android:text="@string/pause_service"

   <Button android:id="@+id/btnStopService"
   android:layout_width="150px"
   android:layout_height="wrap_content"
   android:text="@string/stop_service"

</LinearLayout>

Following will be the content of res/values/strings.xml to define two new constants:

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">HelloWorld</string>
    <string name="action_settings">Settings</string>
    <string name="start_service">Start</string>
    <string name="pause_service">Pause</string>
    <string name="stop_service">Stop</string>

</resources>

Let's try to run our modified Hello World! application we just modified. I assume you had created your AVD while doing environment setup. To run the app from Eclipse, open one of your project's activity files and click Run Eclipse Run Icon icon from the toolbar. Eclipse installs the app on your AVD and starts it and if everything is fine with your setup and application, it will display following Emulator window:

Android LinearLayout 1

Now let's change the orientation of Layout as android:orientation="horizontal" and try to run the same application, it will give following screen:

Android LinearLayout 2

Advertisements
Advertisements