build your first android mobile app

BUILD YOUR FIRST ANDROID MOBILE APP 

This should be a very short (beginner) introduction/tutorial how to create a mobile app for Android. The tutorial is based on API Level 17 and Android 4.2 (Jelly Bean). Our goal is to start from scratch and have at the end a mp/h to km/h converter.

What Do You Need?

1. Basic XML knowledge

2. Basic Java knowledge

3. Basic Eclipse knowledge

4. 2h of your time

 Pre requisites:

1. Before you can start you need the Android SDK and a IDE. Android offers a special bundle for that: Android SDK Bundle

2. Download the bundle, unzip and run the “SDK Manager.exe”.

3. start Eclipse

Create An Android Virtual Machine

Create An Android Virtual Machine

• To run, test and debug your Application you can create and run a virtual android machine on your computer. Later you can deploy your Application to this virtual machine.

• Click on “Windows” at the navigation toolbar

• Open “Android Virtual Device manager“

Create a “New” Virtual Device:

Be sure that “Use Host GPU” is enabled. This allows the AVD to use the Host GPU and this helps to render the AVD much faster.

After that you can start the AVD:

 Create a new Project:

• Open “File“

• “New“

• “Android Application Project“

Choose a new for your Project:

Configure Project:

Configure Launcher Icon:

Here you can choose a Launcher Icon that will be displayed on your mobile phone.

Create a new Activity:

Configure Your Activity

After finishing Eclipse looks similar to that:

Implement the Look & Feel:

Navigate in the package explorer to “/res/layout/” and open “activity_main.xml“

Right-click on “Hello World” and delete

Create static Attributes:

Select “/res/values/strings.xml“

“Add” a new entry

Select the Color entry – press OK and set the following attributes:

Add a few more String(!) Attributes:Name/value: “miles” / “to Miles“Name/value: “kmh” / “to km/h“Name/value: “calc” / “Calculate“

Switch from “Resources” to “strings.xml” and make sure that your code look similar to that snippet:

Add Views

Select “/res/layout/activity_main.xml“Open Android editor via double-clickYou have two possibilities. You can create new Views via drag and drop or you can edit the XML source code. In this tutorial we add the Views via drag and drop So let’s start building our App. At first we have to add a “Text Field” for the input.

Drag this Text Field to your Application.Afterwards select the “Form Widget” section and drag a RadioGroupto your App and make sure that the RadioGroup has twoRadioButtons. Finally you can add a normal Button.

Switch from “Graphical Layout” to “activity_main.xml” and make sure that your code looks similar to that:

Edit view properties

You can edit properties of Views via right-click on the view or via XML.

Navigate to “res/layout/” and open the Graphical Layout of your “activity_main.xml“

right-click on the first Radio Button and open “Edit Text”

• Assign the miles property to the second Radio Button

• Set the “Checked” property for the first Radio Button (Other Properties -> inherited from compoundbutton -> checked -> true)

• Set the “Input type” property for the Text Field to “numberSigned” and “numberDecimal“

• Assign “calc” to the Button and set “calculate” for the “onClick” property (Other Properties -> inherited from view -> onClick)

• Set Background-Color (Right-click on an empty space on your Application -> Edit Background)

After that change the Background should be #eeeeee! I think it can be difficult to see the difference.

Implement the Logic

After we implemented the Frontend-View we have to implement the logical part with Java!

Switch to “src/com.example.tutorialapplication/” and open “MainActivity.java“

This short but useful tutorial courtesy goes to MARC KLEIN.

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