How final keyword works in Android
Solution 1
It is java...final
key word is always the same either in android or not in android. It depends on what you apply to.
For example
Apply to the variable means it cannot be changed after initialized.
Apply to method means it cannot be overload the method.
Apply to the class and you cannot override that class.
Solution 2
Final only lock the reference. Not the object and method inside the reference.
In Android it's just like the way in Java.
For example, final int a = 5
, then a cannot be changed.
Final final TextView campoTexto
; then campoTexto cannot be redefined, but the method inside, like setText or others
, are allowed to use.
A more comprehensive example is Final Deque<Integer> stack = new ArrayDeque<>();
then stack cannot be redefined, but stack.push, pop
and other methods are allowed to use, so the object inside the stack are allowed to change
Solution 3
For variables, the final
keyword means it is basically a constant. In this case, as it is an object, its reference cannot be changed. So basically if you try to assign to final TextView campoTexto
again, the compiler will throw an error out.
Luiz Henrique Ugliano
Starting development for Android and iOS apps.
Updated on June 04, 2022Comments
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Luiz Henrique Ugliano almost 2 years
I Know that in Java we use
final
keyword to variables or something else to make its values not to be changed.What is the difference in using
final
as in the example below?public class MainActivity extends ActionBarActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final TextView campoTexto = (TextView) findViewById(R.id.campoTexto); Button botaoTexto = (Button) findViewById(R.id.botaoTexto); Button botaoCor = (Button) findViewById(R.id.botaoCor); final RelativeLayout fundoTela = (RelativeLayout) findViewById(R.id.fundoTela);