Android Iconography Guide

http://developer.android.com/design/style/iconography.html

Reviewed above Android Iconography design guide, and requirement. All of the standard icon size are defined.

Simplified graphic design in future

In the bitmaps design guide, following doc indicating that low-density (ldpi) resource is optional, if there is hdpi (high-density) resource. Android will auto scale down hdpi to ldpi

Force Program Termination

By calling method finish(), it will indirect call onDestroy() method in the activity.

This will terminate the program immediately

Reason App Icon Not Shows Up in Home Screen

URL: http://developer.android.com/training/basics/activity-lifecycle/starting.html

If either the MAIN action or LAUNCHER category are not declared for one of your activities, then your app icon will not appear in the Home screen's list of apps.

For example:

<activity android:name=".MainActivity" android:label="@string/app_name">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>