Java-android Study (third day)

Android Program Entry point

On the first day, "⑤, program entry point." "The problem with the entry point of the program is mentioned, but more general,

Here, say it again:

 <application        android:allowbackup= "true"          android:icon= "@drawable/ic_launcher"         android: Label= "@string/app_name"         android:theme= "@android: style/ Theme.Black.NoTitleBar.Fullscreen ">        <activity             android:name= ". Mainactivity "            android:screenorientation=" Portrait "            android:label=" @string/app_name " >            <intent-filter>                 <action android:name= " Android.intent.action.MAIN "/&GT;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&Nbsp;       <category android:name= "Android.intent.category.LAUNCHER"/>             </intent-filter>         </activity>    </application>

All activity programs are registered in the Androidmanifest.xml file, so the file is the core profile for the entire Android project.

The android:icon= "@drawable/ic_launcher" configured in the <application> node represents the reference drawable (drawable-hdpi, drawable-ldpi, DRAWABLE-MDPI three folders Import) the icon of the resource configuration, the name of the introduction icon is Ic_launcher;

The android:label= "@string/app_name" configured in the <application> node indicates that the label name of this application is read from the Strings.xml file and the content is app_name corresponding content; Of course, you can also change the title of the activity .

Activity is an active form, and a project application can contain multiple activities.

<intent-filter> <action android:name= "Android.intent.action.MAIN"/> <category android:name= "Android Oid.intent.category.LAUNCHER "/></intent-filter>

The activity contains the above tag, which means that the program is the activity that launches the tag by default:

The method is specified as follows:

①, Android:name= ". Mainactivity "Specifies the. java file in SRC;

②, in the corresponding. java file

protected void OnCreate (Bundle savedinstancestate) {
Super.oncreate (savedinstancestate);
Setcontentview (R.layout.activity_main);

}

where Setcontentview (r.layout.activity_main);, specify the layout XML in Res-layout.

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Java-android Study (third day)