What is the difference between calling LayoutInfla

问题:

I went through some tutorials, and in the Android Doc, it says not to access LayoutInflater directly when instantiating it. Example from the google Doc:

LayoutInflater inflater = (LayoutInflater)context.getSystemService
  (Context.LAYOUT_INFLATER_SERVICE);

The tutorial I went through is this one:

LayoutInflater inflater = LayoutInflater.from(parent.getContext());

So what I don't really understand is what the difference is besides the obvious different code. Any explanation much appreciated. I assume that the Android Doc should be the one we follow, but I am not sure if it makes a difference.

回答1:

If you open up the Android source you can see that the LayoutInflator.from method looks like so:

/**
 * Obtains the LayoutInflater from the given context.
 */
public static LayoutInflater from(Context context) {
    LayoutInflater LayoutInflater =
            (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (LayoutInflater == null) {
        throw new AssertionError("LayoutInflater not found.");
    }
    return LayoutInflater;
}

That means the two lines of code in your question do the same thing. Not sure what the tutorial you read says exactly but I don't see any difference in functionality. Using the from method is nice since it requires a little less typing, that's it.

回答2:

LayoutInflater inflater = (LayoutInflater)context.getSystemService
  (Context.LAYOUT_INFLATER_SERVICE);

You are getting LayoutInflater Service Provider from System Manager

LayoutInflater inflater = LayoutInflater.from(parent.getContext());

You are using static method from LayoutInflater Class

I would say that difference is only in code and how you write this also calling stack but result is same - you will get LayoutInflater.

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Regards