java - DialogInterface.OnClickListener 监听器变量无法解析 [java]

Question

我正在构建一个带有选择列表的警告对话框。我不明白为什么我的 OnClickListener 变量无法解析。

我已将代码单独放在一个单独的 Activity 中并且它可以工作，但在我的主要 Activity 中它没有。

    public void categoryDialogShow(final Context context, String[] categoryOptions){
        final AlertDialog actions;

        AlertDialog.Builder categoryAlert = new AlertDialog.Builder(context);
        categoryAlert.setTitle("Choose a Category");

        categoryAlert.setItems(categoryOptions, actionListener);
//=============================================================
//==============actionListener cannot be resolved to a variable
//=============================================================
        categoryAlert.setNegativeButton("Cancel", null);
        actions = categoryAlert.create();

        DialogInterface.OnClickListener actionListener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
          //goto category list with which as the category
        }
      };
      actions.show();
}

这是没有问题的 Activity :

public class MainActivity extends ActionBarActivity {

    AlertDialog actions;

      @Override
      protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Activity");
        Button button = new Button(this);
        button.setText("Click for Options");
        button.setOnClickListener(buttonListener);

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Choose an Option");
        String[] options = { "A", "B", "C" };
        builder.setItems(options, actionListener);
        builder.setNegativeButton("Cancel", null);
        actions = builder.create();

        setContentView(button);
      }
      DialogInterface.OnClickListener actionListener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
          switch (which) {
          case 0: // Delete
            break;
          case 1: // Copy
            break;
          case 2: // Edit
            break;
          default:
            break;
          }
        }
      };
      View.OnClickListener buttonListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
          actions.show();
        }
      };
}

Answer 1

只需将声明移至需要引用的位置即可:

public void categoryDialogShow(final Context context, String[] categoryOptions){
    final AlertDialog actions;
    DialogInterface.OnClickListener actionListener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
          //goto category list with which as the category
        }
      };

    AlertDialog.Builder categoryAlert = new AlertDialog.Builder(context);
    categoryAlert.setTitle("Choose a Category");

    categoryAlert.setItems(categoryOptions, actionListener);
    categoryAlert.setNegativeButton("Cancel", null);
    actions = categoryAlert.create();


  actions.show();
}

它在另一个类中起作用的原因是 actionListener 引用是一个类成员变量，正如我所怀疑的那样。 请注意，声明不在任何方法内。你可以对你的新 Activity 做同样的事情:

DialogInterface.OnClickListener actionListener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
          //goto category list with which as the category
        }
      };

public void categoryDialogShow(final Context context, String[] categoryOptions){
    final AlertDialog actions;

    AlertDialog.Builder categoryAlert = new AlertDialog.Builder(context);
    categoryAlert.setTitle("Choose a Category");

    categoryAlert.setItems(categoryOptions, actionListener);
    categoryAlert.setNegativeButton("Cancel", null);
    actions = categoryAlert.create();


  actions.show();
}