android:enable and services

问题:

I m currently learning how create and use services on android. I looked on the android SDK for further help and i found the android:enable=[true | false].

in the SDK is said that:

The and attributes must both be "true" (as they both are by default) for the service to be enabled. If either is "false", the service is disabled; it cannot be instantiated.

So i would like to know what is the interest of/ why (in general)

• setting the application enables as "false".
• setting the service enable as "false".

I say that if we put service enable as false there is no way to call that service, so why we create that service in the first place?

Thank you and sorry for such long message.

回答1:

New SAF(Storage Access Framework) is a good example of use of android:enabled attribute. http://developer.android.com/guide/topics/providers/document-provider.html

The android:enabled attribute set to a boolean value defined in a resource file. The purpose of this attribute is to disable the provider on devices running Android 4.3 or lower. For example,

android:enabled="@bool/atLeastKitKat" 

In addition to including this attribute in the manifest, you need to do the following: In your bool.xml resources file under res/values/, add this line:

<bool name="atLeastKitKat">false</bool> 

In your bool.xml resources file under res/values-v19/, add this line:

<bool name="atLeastKitKat">true</bool>

回答2:

setting the application enables as "false".

I know of no good reason for doing this.

I say that if we put service enable as false there is no way to call that service, so why we create that service in the first place?

Generally, that is true. android:enabled is, in effect, inherited for all components, so it is not unique to services. Here are scenarios where it might be used:

• Activity: you want to have a second icon in the launcher, but only if the user purchases something through in-app purchasing (e.g., upgrades to "Pro" features)

• BroadcastReceiver: you want to get control at boot time via ACTION_BOOT_COMPLETED, but you do not need that all of the time

• Service and ContentProvider: you have a family of apps, where you only need (and want) one implementation of the service/content provider to be around, even if more than one app from your family are installed by the user

In these cases, you might have the component disabled (android:enabled="false") in the manifest, and use PackageManager and setComponentEnabledSetting() to conditionally enable them later on.