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Judul : Android : Hello World Example
link : Android : Hello World Example
Artikel yang anda baca saat ini Android : Hello World Example dengan alamat link https://idkingcode.blogspot.com/2016/08/android-hello-world-example.html
Judul : Android : Hello World Example
link : Android : Hello World Example
Android : Hello World Example
In this session, you will know about how to create the simple Hello World application in Android. We are creating first simple example of android using Eclipse IDE. For creating this follow this steps :
Create new Android project
Write message (optional)
Run Android Application
Create Android Application
The first step is to create a simple Android Application using Eclipse IDE. Follow the option File > New > Project > Android New Application wizard from the wizard list. Now give name of your application as HelloWorld using the Wizard window as follows :
Click On Next and follow the instructions provided and keep all other entries as defult till the final stpe. Once your project is created sucessfully, you will have following project screen —
Anatomy of Android Application
Before you run your app, you should be aware of a few directories and files in the Android project –
S.N.Folder, File & Description
1srcThis contains the .java source files for your project. By default, it includes an MainActivity.java source file having an activity class that runs when your app is launched using the app icon.
2gen
This contains the .R file, a compiler-generated file that references all the resources found in your project. You should not modify this file.
3bin
This folder contains the Android package files .apk built by the ADT during the build process and everything else needed to run an Android application.
4res/drawable-hdpi
This is a directory for drawable objects that are designed for high-density screens.
5res/layout
This is a directory for files that define your app’s user interface.
6res/values
This is a directory for other various XML files that contain a collection of resources, such as strings and colours definitions.
7AndroidManifest.xml
This is the manifest file which describes the fundamental characteristics of the app and defines each of its components.
Following section will give brief overview few of the important application files..The Main Activity File
The main activity code is a Java file MainActivity.java. This is the actual application file which ultimately gets covered to a Dalvik executable and runs your application. Following is the defult code generated by the application wizard for Hello World Android app. –
Here, R.layout.activity_main refers to activity_main.xml file located in the res/layout folder. The onCreate() method is one of many methods that are figured when an activity is loaded.
The Manifest File
Whatever component you develop as a part of your application, you must declare all its components in a manifest.xml which resides at the root of the application project directory. This file works as an interface between Android Operating System and your application, so if you do not declare your components in this file, then it will not be considered by the OS. For e.g., a default manifest file will look like as following file.–
Here … tags enclosed the components related to the application. Attribute android:icon will point to the application icon available under res/drawable-hdpi. The application uses the image named ic_launcher.png located in the drawable folders
The tag is used to specify an activity and android:name attribute specifies the fully qualified class name of the Activity subclass and the android:label attributes specifies a string to use as the label for the activity. You can specify multiple activities using tags.
The action for the intent filter is named android.intent.action.MAIN to indicate that this activity serves as the entry point for the application. The category for the intent-filter is named android.intent.category.LAUNCHER to indicate that the application can be launched from the device’s launcher icon.
The @string refers to the strings.xml file explained below. Hence, @string/app_name refers to the app_name string defined in the strings.xml file, which is “HelloWorld“. Similar way, other strings get populated in the application.
Following is the list of tags which you will use in your manifest file to specify different Android application components:
element for activities
element for services
elements for broadcast receivers
elements for content providers
The Strings File
The strings.xml file is located in the res/values folder and it contains all the text that your application uses. For example, the names of buttons, labels, default text, and similar types of strings go into this file. This file is responsible for their textual content. For example, a default strings file will look like as following file −
The R File
The gen/com.example.helloworld/R.java file is the glue between the activity Java files likeMainActivity.java and the resources like strings.xml. It is an automatically generated file and you should not modify the content of the R.java file. Following is a sample of R.java file −
The Layout File
The activity_main.xml is a layout file available in res/layout directory, that is referenced by your application when building its interface. You will modify this file very frequently to change the layout of your application. For your “Hello World ” application, this file will have following content related to default layout −
This is an example of simple RelativeLayout which we will study in a separate chapter. TheTextView is an Android control used to build the GUI and it have various attributes like android:layout_width, android:layout_height etc which are being used to set its width and height etc.. The @string refers to the strings.xml file located in the res/values folder. Hence, @string/hello_world refers to the hello string defined in the strings.xml file, which is “Hello World“.
Running the Application
Let’s try to run our Hello World application we just created. I assume you had created your AVD while doing environment set-up. To run the app from Eclipse, open one of your project’s activity files and click Run icon from the tool bar. Eclipse installs the app on your AVD and starts it and if everything is fine with your set-up and application, it will display following Emulator window
Create new Android project
Write message (optional)
Run Android Application
Create Android Application
The first step is to create a simple Android Application using Eclipse IDE. Follow the option File > New > Project > Android New Application wizard from the wizard list. Now give name of your application as HelloWorld using the Wizard window as follows :
Click On Next and follow the instructions provided and keep all other entries as defult till the final stpe. Once your project is created sucessfully, you will have following project screen —
Anatomy of Android Application
Before you run your app, you should be aware of a few directories and files in the Android project –
S.N.Folder, File & Description
1srcThis contains the .java source files for your project. By default, it includes an MainActivity.java source file having an activity class that runs when your app is launched using the app icon.
2gen
This contains the .R file, a compiler-generated file that references all the resources found in your project. You should not modify this file.
3bin
This folder contains the Android package files .apk built by the ADT during the build process and everything else needed to run an Android application.
4res/drawable-hdpi
This is a directory for drawable objects that are designed for high-density screens.
5res/layout
This is a directory for files that define your app’s user interface.
6res/values
This is a directory for other various XML files that contain a collection of resources, such as strings and colours definitions.
7AndroidManifest.xml
This is the manifest file which describes the fundamental characteristics of the app and defines each of its components.
Following section will give brief overview few of the important application files..The Main Activity File
The main activity code is a Java file MainActivity.java. This is the actual application file which ultimately gets covered to a Dalvik executable and runs your application. Following is the defult code generated by the application wizard for Hello World Android app. –
Here, R.layout.activity_main refers to activity_main.xml file located in the res/layout folder. The onCreate() method is one of many methods that are figured when an activity is loaded.
The Manifest File
Whatever component you develop as a part of your application, you must declare all its components in a manifest.xml which resides at the root of the application project directory. This file works as an interface between Android Operating System and your application, so if you do not declare your components in this file, then it will not be considered by the OS. For e.g., a default manifest file will look like as following file.–
Here … tags enclosed the components related to the application. Attribute android:icon will point to the application icon available under res/drawable-hdpi. The application uses the image named ic_launcher.png located in the drawable folders
The tag is used to specify an activity and android:name attribute specifies the fully qualified class name of the Activity subclass and the android:label attributes specifies a string to use as the label for the activity. You can specify multiple activities using tags.
The action for the intent filter is named android.intent.action.MAIN to indicate that this activity serves as the entry point for the application. The category for the intent-filter is named android.intent.category.LAUNCHER to indicate that the application can be launched from the device’s launcher icon.
The @string refers to the strings.xml file explained below. Hence, @string/app_name refers to the app_name string defined in the strings.xml file, which is “HelloWorld“. Similar way, other strings get populated in the application.
Following is the list of tags which you will use in your manifest file to specify different Android application components:
element for activities
element for services
elements for broadcast receivers
elements for content providers
The Strings File
The strings.xml file is located in the res/values folder and it contains all the text that your application uses. For example, the names of buttons, labels, default text, and similar types of strings go into this file. This file is responsible for their textual content. For example, a default strings file will look like as following file −
The R File
The gen/com.example.helloworld/R.java file is the glue between the activity Java files likeMainActivity.java and the resources like strings.xml. It is an automatically generated file and you should not modify the content of the R.java file. Following is a sample of R.java file −
The Layout File
The activity_main.xml is a layout file available in res/layout directory, that is referenced by your application when building its interface. You will modify this file very frequently to change the layout of your application. For your “Hello World ” application, this file will have following content related to default layout −
This is an example of simple RelativeLayout which we will study in a separate chapter. TheTextView is an Android control used to build the GUI and it have various attributes like android:layout_width, android:layout_height etc which are being used to set its width and height etc.. The @string refers to the strings.xml file located in the res/values folder. Hence, @string/hello_world refers to the hello string defined in the strings.xml file, which is “Hello World“.
Running the Application
Let’s try to run our Hello World application we just created. I assume you had created your AVD while doing environment set-up. To run the app from Eclipse, open one of your project’s activity files and click Run icon from the tool bar. Eclipse installs the app on your AVD and starts it and if everything is fine with your set-up and application, it will display following Emulator window
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Artikel yang anda baca saat ini Android : Hello World Example dengan alamat link https://idkingcode.blogspot.com/2016/08/android-hello-world-example.html
Android : Hello World Example
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