java 错误：无法为最终变量赋值

Error: cannot assign a value to final variable

提问by Goji Berry

I am facing the following issue with Android Studio

我在 Android Studio 中面临以下问题

public class MainActivity extends AppCompatActivity {

  @Override
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final int numeroHomem = 0;
    final int numeroMulher = 0;
    final int numeroPessoas = 0;

    final TextView campoTexto = (TextView) findViewById(R.id.pessoas);
    final Button botaoHomem = (Button) findViewById(R.id.homem);
    final Button botaoMulher = (Button) findViewById(R.id.mulher);
    final Button botaoReset = (Button) findViewById(R.id.reset);

     botaoHomem.setOnClickListener(new Button.OnClickListener(){
        public void onClick(View v){
            numeroHomem++;
            numeroPessoas++;
            String mensagem = Integer.toString(numeroPessoas);
            campoTexto.setText("Total: " + mensagem + " pessoas");
            botaoHomem.setText(Integer.toString(numeroHomem));
         }
     });
 } }

error: cannot assign a value to final variable numeroHomem
error: cannot assign a value to final variable numeroPessoas

错误：无法为最终变量 numeroHomem 赋值
错误：无法为最终变量 numeroPessoas 赋值

回答by Ali

you cannot change finalvariable after initialization

final初始化后不能更改变量

what you can do is declare your variable in your class instead of onCreate()

你可以做的是在你的类中声明你的变量而不是 onCreate()

public class MainActivity extends AppCompatActivity {

    int numeroHomem = 0;
    int numeroMulher = 0;
    int numeroPessoas = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);


      final TextView campoTexto = (TextView) findViewById(R.id.pessoas);
      final Button botaoHomem = (Button) findViewById(R.id.homem);
      final Button botaoMulher = (Button) findViewById(R.id.mulher);
      final Button botaoReset = (Button) findViewById(R.id.reset);

      botaoHomem.setOnClickListener(new Button.OnClickListener(){
            public void onClick(View v){
                numeroHomem++;
                numeroPessoas++;
                String mensagem = Integer.toString(numeroPessoas);
                campoTexto.setText("Total: " + mensagem + " pessoas");
                botaoHomem.setText(Integer.toString(numeroHomem));
            }
          });
    }
}

回答by clabe45

As your comment suggests, the message the compiler requires all the variables, used in lambdas, to be effectively finalimplies that you need to set your variable to instance properties, so the compiler will know where to look.

正如您的评论所暗示的那样，该消息the compiler requires all the variables, used in lambdas, to be effectively final暗示您需要将变量设置为实例属性，因此编译器将知道在哪里查找。

回答by EasyJoin Dev

This is not an issue of Android Studio or Android in general. Once you have declare an object as finalyou can't change it. Create, for example, an utility class, declare in that class the numeroHomemand numeroPessoasas public staticand modify them in the onClickmethod.

这通常不是 Android Studio 或 Android 的问题。一旦你声明了一个对象，final你就不能改变它。例如，创建一个实用程序类，在该类中声明numeroHomem和numeroPessoasaspublic static并在onClick方法中修改它们。

回答by asalamon74

If you declare numeroHomemand numeroPessoasas final variables then you cannot increase their values later using numeroHomem++and numeroPessoas++. Just remove the final keywords.

如果将numeroHomemand声明numeroPessoas为 final 变量，则以后不能使用numeroHomem++and增加它们的值numeroPessoas++。只需删除最终关键字。

回答by jigar savaliya

You can not change the value of final variable, simply remove final from you variable.

您不能更改 final 变量的值，只需从变量中删除 final。

int numeroHomem = 0;
int numeroMulher = 0;
int numeroPessoas = 0;