Why does putExtra take a key value pair and not just a value?

Question

I am going through some of the Android development tutorials, and I just came up with this general question:

Why is it that the intent.putExtra method takes a key value pair and not just a value?

If I want to pass a string to the new Intent , why not just pass the String ? What benefits does the key have?

Answer 1

You can add more than one object to your Intent so you could do this:

intent.putExtra("name", "My Name");
intent.putExtra("age", 30);

If you want to get the some of the data back you need to specify which using the key:

intent.getStringExtra("name"); // returns "My Name"
intent.getIntExtra("age");     // returns 30

Answer 2

非常简单：键允许您传递多个String（或Integer，Parcalable等）并将它们分开。