What's T[] Object?

the constructor of ArrayAdapter is as follows: ArrayAdapter(Context context, int textViewResourceId, T[] objects) im new to java & android, i didn't see the data type T[] befor

Solution 1:

The T is either a concrete class type (unlikely), or it is a class generic. Look at your class heading to see if this is the case.

IE

Class SomeClassType<T> {}

Tutorials on generics and how they work can be found here http://docs.oracle.com/javase/tutorial/java/generics/index.html

Solution 2:

http://docs.oracle.com/javase/tutorial/java/generics/gentypes.html

It is a generic type, which means that you can give any type you want to replace the T generic type.

Solution 3:

T[] means generic type. Here is documentation on generics.

Solution 4:

As has been mentioned, T in this case refers to a generic type. In other words, an ArrayAdapter can be used to handle objects of any type in order to bind the textual representation of those objects to Android TextViews.

A simple example would be to use an array of type String...

ArrayAdapter<String> myArrayAdapter;
String[] myArray = new String[] { "Hello", "World" } ;
myArrayAdapter = new ArrayAdapter<String>(this, R.id.my_textview, myArray);

Using Strings for ArrayAdapter is probably the most common approach although any object which implements toString() to return something meaningful can be used...

ArrayAdapter<SomeObject> myArrayAdapter;
SomeObject[] myArray = new SomeObject[] { ... } ;
myArrayAdapter = new ArrayAdapter<SomeObject>(this, R.id.my_textview, myArray);

As long as SomeObject.toString() is implemented then the TextView represented by the resource id R.id.my_textview will be bound to its return value.