问题
I've found the R.string pretty awesome for keeping hardcoded strings out of my code, and I'd like to keep using it in a utility class that works with models in my application to generate output. For instance, in this case I am generating an email from a model outside of the activity.
Is it possible to use getString outside a Context or Activity? I suppose I could pass in the current activity, but it seems unnecessary. Please correct me if I'm wrong!
Edit: Can we access the resources without using Context?
回答1:
Yes, we can access resources without using `Context`
You can use:
Resources.getSystem().getString(android.R.string.somecommonstuff)
... everywhere in your application, even in static constants declarations. Unfortunately, it supports the system resources only.
For local resources use this solution. It is not trivial, but it works.
回答2:
Unfortunately, the only way you can access any of the string resources is with a Context (i.e. an Activity or Service). What I've usually done in this case, is to simply require the caller to pass in the context.
回答3:
In MyApplication, which extends Application:
public static Resources resources;
In MyApplication's onCreate:
resources = getResources();
Now you can use this field from anywhere in your application.
回答4:
BTW, one of the reason of symbol not found error may be that your IDE imported android.R; class instead of yours one. Just change import android.R; to import your.namespace.R;
So 2 basic things to get string visible in the different class:
//make sure you are importing the right R class
import your.namespace.R;
//don't forget about the context
public void some_method(Context context) {
context.getString(R.string.YOUR_STRING);
}
回答5:
Unique Approach
App.getRes().getString(R.string.some_id)
This will work everywhere in app. (Util class, Dialog, Fragment or any class in your app)
(1) Create or Edit (if already exist) your Application class.
import android.app.Application;
import android.content.res.Resources;
public class App extends Application {
private static App mInstance;
private static Resources res;
@Override
public void onCreate() {
super.onCreate();
mInstance = this;
res = getResources();
}
public static App getInstance() {
return mInstance;
}
public static Resources getResourses() {
return res;
}
}
(2) Add name field to your manifest.xml <application tag.
<application
android:name=".App"
...
>
...
</application>
Now you are good to go. Use App.getRes().getString(R.string.some_id) anywhere in app.
回答6:
If you have a class that you use in an activity and you want to have access the ressource in that class, I recommend you to define a context as a private variable in class and initial it in constructor:
public class MyClass (){
private Context context;
public MyClass(Context context){
this.context=context;
}
public testResource(){
String s=context.getString(R.string.testString).toString();
}
}
Making an instant of class in your activity:
MyClass m=new MyClass(this);
回答7:
This should get you access to applicationContext from anywhere allowing you to get applicationContext anywhere that can use it; Toast, getString(), sharedPreferences, etc.
The Singleton:
package com.domain.packagename;
import android.content.Context;
/**
* Created by Versa on 10.09.15.
*/
public class ApplicationContextSingleton {
private static PrefsContextSingleton mInstance;
private Context context;
public static ApplicationContextSingleton getInstance() {
if (mInstance == null) mInstance = getSync();
return mInstance;
}
private static synchronized ApplicationContextSingleton getSync() {
if (mInstance == null) mInstance = new PrefsContextSingleton();
return mInstance;
}
public void initialize(Context context) {
this.context = context;
}
public Context getApplicationContext() {
return context;
}
}
Initialize the Singleton in your Application subclass:
package com.domain.packagename;
import android.app.Application;
/**
* Created by Versa on 25.08.15.
*/
public class mApplication extends Application {
@Override
public void onCreate() {
super.onCreate();
ApplicationContextSingleton.getInstance().initialize(this);
}
}
If I´m not wrong, this gives you a hook to applicationContext everywhere, call it with ApplicationContextSingleton.getInstance.getApplicationContext();
You shouldn´t need to clear this at any point, as when application closes, this goes with it anyway.
Remember to update AndroidManifest.xml to use this Application subclass:
<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.domain.packagename"
>
<application
android:allowBackup="true"
android:name=".mApplication" <!-- This is the important line -->
android:label="@string/app_name"
android:theme="@style/AppTheme"
android:icon="@drawable/app_icon"
>
Please let me know if you see anything wrong here, thank you. :)
回答8:
The best approach from the response of Khemraj:
App class
class App : Application() {
companion object {
lateinit var instance: Application
lateinit var resourses: Resources
}
// MARK: - Lifecycle
override fun onCreate() {
super.onCreate()
instance = this
resourses = resources
}
}
Declaration in the manifest
<application
android:name=".App"
...>
</application>
Constants class
class Localizations {
companion object {
val info = App.resourses.getString(R.string.info)
}
}
Using
textView.text = Localizations.info
回答9:
It's better to use something like this without context and activity:
Resources.getSystem().getString(R.string.my_text)
回答10:
Here's what I did, In your MainActivity, create a static variable for context as shown below:
public static Context mContext;
and in the onCreate() initialise mContext to this;
mContext = this;
Then, in the file where you want to access context, say,
private Context context = MainActivity.mContext;
Now, you can get a string resource in the following manner,
String myString = context.getResources().getString(R.string.resource_id);
回答11:
I used
getContext().getApplicationContext().getString(R.string.nameOfString);
It works for me.
来源：https://stackoverflow.com/questions/4253328/getstring-outside-of-a-context-or-activity