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Building  “HelloWorld”Android Application  Step by Step.                      1
Topics• Building blocks of Android Application  > Activities  > Layout resource files  > AndroidManifest.xml  > Resource f...
Building Blocks ofAndroid Application
Building Blocks of Android Application• Activity classes• Layout resource files• Resource files  > strings.xml• AndroidMan...
Building Blocks of Android Application
Activity Class• Each Activity class typically represents a screen  > Like a JSP page in a Web application• The onCreate() ...
Activity Class Examplepackage com.javapassion;import android.app.Activity;import android.os.Bundle;public class HelloWorld...
Layout Resource Files• Every screen has a corresponding layout  resource file  > Unless you create UI programmatically• Ea...
Layout Resource File Example
Resource Files - strings.xml• Let you define the text strings of your  applications in a well-known file  > Rather than in...
strings.xml Resource File
AndroidManifest.xml file• Every application must have a manifest file  called AndroidManifest.xml file (with precisely  th...
Info. in AndroidManifest.xml file• Java package for the application.  > The package name serves as a unique identifier for...
AndroidManifest.xml
R.java• Automatically created by Android system for all  resources defined
R.java
Thank you
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Android stepbystep

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Transcript of "Android stepbystep"

  1. 1. Building “HelloWorld”Android Application Step by Step. 1
  2. 2. Topics• Building blocks of Android Application > Activities > Layout resource files > AndroidManifest.xml > Resource files - strings.xml > R.java
  3. 3. Building Blocks ofAndroid Application
  4. 4. Building Blocks of Android Application• Activity classes• Layout resource files• Resource files > strings.xml• AndroidManifest.xml• R.java (automatically created from resource files)• Android library (automatically configured)
  5. 5. Building Blocks of Android Application
  6. 6. Activity Class• Each Activity class typically represents a screen > Like a JSP page in a Web application• The onCreate() method of Activity class gets called by the Android system when your Activity starts > You create your UI inside the onCreate() method• Every Activity has to be described in the AndroidManifest.xml file• An Activity is typically chosen as a starting one of your application - like a class that has a main() method in Java > Special configuration in AndroidManifest.xml
  7. 7. Activity Class Examplepackage com.javapassion;import android.app.Activity;import android.os.Bundle;public class HelloWorldActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //Create UI using Layout resource file setContentView(R.layout.main); }}
  8. 8. Layout Resource Files• Every screen has a corresponding layout resource file > Unless you create UI programmatically• Each activity class specifies which layout resource file to use for each screen it represents > Using setContentView(R.layout.main);• Are located under /res/layout directory > /res/layout/main.xml layout resource file is referred to as R.layout.main
  9. 9. Layout Resource File Example
  10. 10. Resource Files - strings.xml• Let you define the text strings of your applications in a well-known file > Rather than in Java code > Rather than in Layout resource files• The strings are then referred to through the names assigned to them > The mapping is done through R.java > @string/hello (in the layout resource file) > R.string.hello (in the Java code)• Located under /res/values directory
  11. 11. strings.xml Resource File
  12. 12. AndroidManifest.xml file• Every application must have a manifest file called AndroidManifest.xml file (with precisely that name) in its root directory.• The manifest presents essential information about the application to the Android system, information the system must have before it can run any of the applications code.
  13. 13. Info. in AndroidManifest.xml file• Java package for the application. > The package name serves as a unique identifier for the application.• Activities > One activity is designated as a starting Activity <activity android:name=".HelloWorldActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>
  14. 14. AndroidManifest.xml
  15. 15. R.java• Automatically created by Android system for all resources defined
  16. 16. R.java
  17. 17. Thank you
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