不能引用非最终变量i在不同的方法中定义的内部类里面 [英] Cannot refer to a non-final variable i inside an inner class defined in a different method

问题描述

我有不能引用非最终变量i在不同的方法中定义的内部类里面的错误...我在哪里去了？......我刚开始学习Android和Java编程..

i have "Cannot refer to a non-final variable i inside an inner class defined in a different method" error... Where am i going wrong?... I just started to learn android and java programming..

public class Tictac extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

        Button button[] = new Button[9];
        button[0]= (Button) findViewById(R.id.button1);
        button[1] = (Button) findViewById(R.id.button2);
        button[2] = (Button) findViewById(R.id.button3);
        button[3] = (Button) findViewById(R.id.button4);
        button[4] = (Button) findViewById(R.id.button5);
        button[5] = (Button) findViewById(R.id.button6);
        button[6] = (Button) findViewById(R.id.button7);
        button[7] = (Button) findViewById(R.id.button8);
        button[8] = (Button) findViewById(R.id.button9);


        final TextView text = (TextView) findViewById(R.id.textView1);

        final ImageView img[] = new ImageView[9];
        img[0] = (ImageView) findViewById(R.id.img1);
        img[1] = (ImageView) findViewById(R.id.img2);
        img[2] = (ImageView) findViewById(R.id.img3);
        img[3] = (ImageView) findViewById(R.id.img4);
        img[4] = (ImageView) findViewById(R.id.img5);
        img[5] = (ImageView) findViewById(R.id.img6);
        img[6] = (ImageView) findViewById(R.id.img7);
        img[7] = (ImageView) findViewById(R.id.img8);
        img[8] = (ImageView) findViewById(R.id.img9);
        final ImageView imSq[] = new ImageView[9];
        imSq[0] = (ImageView) findViewById(R.id.imSq1);
        imSq[1] = (ImageView) findViewById(R.id.imSq2);
        imSq[2] = (ImageView) findViewById(R.id.imSq3);
        imSq[3] = (ImageView) findViewById(R.id.imSq4);
        imSq[4] = (ImageView) findViewById(R.id.imSq5);
        imSq[5] = (ImageView) findViewById(R.id.imSq6);
        imSq[6] = (ImageView) findViewById(R.id.imSq7);
        imSq[7] = (ImageView) findViewById(R.id.imSq8);
        imSq[8] = (ImageView) findViewById(R.id.imSq9);


        for(int i =0;i <=8;i++){
        if(i%2==0){
             button[i].setOnClickListener(new View.OnClickListener() {
                     public void onClick(View v) {
        **HERE-->**       img[i].setVisibility(2);
                         text.setText("COOL");

                    }
                    });
        }
        else{   
             button[i].setOnClickListener(new View.OnClickListener() {
                     public void onClick(View v) {
         **HERE-->**        imSq[i].setVisibility(2);
                         text.setText("COOL");

                    }
                    });
    }



        }

}      

}

推荐答案

该错误消息说，究竟出了什么问题：在我变量不是最终的，但你试图引用它的匿名内部类中。

The error message says exactly what's wrong: the i variable isn't final, but you're trying to refer to it within an anonymous inner class.

您可以这样做：

for (int i = 0; i <= 8;i++) {
  if (i % 2 == 0) {
     final int j = i;
     button[i].setOnClickListener(new View.OnClickListener() {
         public void onClick(View v) {
           img[j].setVisibility(2);
           text.setText("COOL");
         }
     });
  }
}

下面我们就一起来的复制的变量我中，并将其分配给最终的变量Ĵ，然后我们可以在匿名内部类中使用。另外，如果你不关心的阵列变化的可能性，你可以这样做：

Here we take a copy of the variable i, and assign it to a final variable j, which we can then use within the anonymous inner class. Alternatively, if you don't care about the possibility of the array changing, you could do:

for (int i = 0; i <= 8;i++) {
  if (i % 2 == 0) {
     final ImageView imageView = img[i];
     button[i].setOnClickListener(new View.OnClickListener() {
         public void onClick(View v) {
           imageView.setVisibility(2);
           text.setText("COOL");
         }
     });
  }
}

从第8.1节。 3 Java语言规范的的：

使用的任何局部变量，形式化方法参数或异常处理参数，但在一个内部类未声明必须声明为final。任何局部变量，使用，但没有宣布在内部类必须被明确赋值（§16）的内部类的主体了。

Any local variable, formal method parameter or exception handler parameter used but not declared in an inner class must be declared final. Any local variable, used but not declared in an inner class must be definitely assigned (§16) before the body of the inner class.

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