Passing Activity Context to constructors to use in

问题:

Is it bad practice to pass the Context to a constructor and save it as a private variable for internal use? The other option is to pass the Context as a parameter to methods that need it.

Which is a better option? I have a feeling that passing to the constructor might result in memory leaks accidentally.

回答1:

Often, all you need is the ApplicationContext, so what you can do is pass this.getApplicationContext() instead of just this. Your app context exists for the lifetime of the app anyway, so it's not a memory leak.

回答2:

It depends on the lifetime of your object. If you're sure the Object will only ever be used internally by your Activity you'd be OK passing the Context to the constructor, otherwise don't pass the Context in.

If an Object has a reference to the Context this will stop the Activity being Garbage Collected, and since an Activity has references to all its views this means you can easily leak a lot of memory very quickly.

It's easy to catch yourself out here since things like device rotations cause Activities to be re-created and it's easy to hang on to an Object without realising.

So it's probably best to be on the safe side and pass in the Context as and when you need it.

回答3:

In the main application (which launches), declare a variable appContext: "public static Context appContext;" Then, in the onCreate() method for this main application, assign: "appContext = this;" Because appContext is public, any other class in this package can then use appContext to track down the XML resources. Is this any better (from memory standpoint)?

Even better might be to declare the Resources object as public static in the main application and then use it elsewhere, since resources is all you need.