Android Development--the first event

I. Create a project

1. 1

   Project Name: myactivity

   Package Name: com.iflytek.myactivity

2. 2

   To facilitate learning, do not tick create Activity. Then finish, the project is created

   END

Two. Create an event

1. 1

   Create a package. The package is named: Com.iflytek.myactivity.

   Create method: Right-click src directory->new->package, fill in the package name can

2. 2

   Create a class that is named Activityfirst.

   Create method: Right-click the package->new->class just now.

3. 3

   Because you want to create an activity, you must inherit from the activity base class with the following code:

4. 4

   Create an activity, code, explained below:

   We have added the following method OnCreate in Activityfirst. Based on the activity's life cycle, when an activity is initialized, a oncreate is first invoked to create an activity. So, we added the OnCreate method.

   Bundle: This type is similar to the map type and stores the data in a key-value manner;

   Savedinstancestate: It is useful to save the state of an activity, which is called before an activity is completed. For example, using a reader to read a novel, close the reader, the next time you open, will still stay in the last place to see.

   Super.oncreate (): Super is a property or method that calls the parent class, here is the OnCreate method that first runs the parent class

    

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Three. Creating and loading layouts

2. 1

   The Android program is designed with logic and view separation. I just implemented the logic in Java code and created the activity, but there's nothing in this activity. So, you need to make a layout for him.

4. 2

   ->new->android the XML file in the Res/layout directory to create a layout file. The command is Layout_first.

   When the creation is complete, select Layout_first.xml to switch to edit mode. Add the following in your code:

   <button

   Android:id= "@+id/button_1"

   Android:layout_width= "Match_parent"

   android:layout_height= "Wrap_content"

   android:text= "Button 1"

   />

   Explained below:

   1) <button/>: This is a button control, we add a button in the current layout file;

   2) Android:id: Unique identifier for this button. Can be referenced in code; "@+id/button_1" means to add a unique ID to the button named Button_1

   3) Android:layout_width:layout is the layout meaning, Layout_width is the width of the control. and is relative to the width of its parent element. Only match_parent (full space), wrap_parent (just to show exactly what you want to show)

   Android:text: What to display

6. 3

   The layout is complete and the layout is added to the code below

   Back to the previous code, add the following line:

   Setcontentview (R.layout.layout_first);

   This means: The current activity uses the Layout_first layout file for layout.

   R: is a class, layout is an inner class of R, and Layout_first is a class variable in this inner class.

   END

Four. Registering in the Androidmanifest file

2. &NBSP;

   All activities need to be registered in this file, add code as follows

   <activity 

               android:name= "Com.iflytek.myactivity.ActivityFirst"

               android:label= "This is firstactivity"

               < Intent-filter>

                   <action android:name= " Android.intent.action.MAIN "/>

                       <categor Y android:name= "Android.intent.category.LAUNCHER"/>

                   & Lt;/intent-filter>

               </activity>

   Android:name   The name of the activity is the package name + class name, because you need to tell the file which class you register, he can find this activity;

   Android:label   acvitity tags, after the software opens, This activity's title bar displays the name.

   Intent-filter: Intent filter, not much to say here, in short, with a few words, it means to use this actitity as our main activity of this program

4. 2

   OK, right click on the myactivity, choose Run as->android application, get it running

Android Development--the first event