How to use getSystemService in a non-activity class?
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30-09-2019 - |
문제
I am building an application which triggers an alarm via AlarmManager.
I would like to be able to call the Alarm via it's own non-activity class, but since I am not extending Activity, I don't appear to have any 'context'. This concept confuses me, and I've read the sdk docs.
How would I go about using:
alarmTest = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
in my non-activty class?
Also, I'm assuming getting context will allow me to use SharedPrefs and Intents in my non-activity class as well?
해결책
You can pass the context to the non-activity class which is the preferred way or you could encapsulate the base context of the application to a singleton which would allow you to access the context anywhere within the application. At some cases this might be a good solution but in others its certainly not a good one.
Anyway, if you want to trigger an alarm via the AlarmManager
I'm pretty sure the alarm should inherit from a Service
or better yet from IntentService
and in such cases you have access to the context via this.getBaseContext()
or this.getApplicationContext()
다른 팁
Service
and Activity
inherit from Context
- so when you are calling getSystemService
in these classes, you are really calling super.getSystemService
.
If you want to have a Context
available in another class, you can pass one as an argument to a method of that class, keep a reference to it, etc.
Edit: Code sample. But seriously, it is extremely basic - if you understand inheritance and methods.
class MyActivity extends Activity { // Activity extends Context, so MyActivity also extends Context
void someMethod() {
MyOtherClass.useStaticContext(this);
MyOtherClass instance = new MyOtherClass();
instance.useInstanceContext(this.getApplicationContext());
}
}
class MyOtherClass {
static void useStaticContext(Context context) {
}
void useInstanceContext(Context context) {
}
}
You can try the following, it allows you to get the current context the view is running through.
alarmTest = (AlarmManager)this.getContext().getSystemService(Context.ALARM_SERVICE);
You need to pass a context into the non-activity class.