错误：公用类型TodoListItemView必须在其自己的文件中定义。 安卓 日食

Question

Error: The public type TodoListItemView must be defined in its own file. (Line: public class TodoListItemView extends TextView { )

    package com.kisinivan.todolist;

import java.util.ArrayList;

import android.os.Bundle;
import android.app.Activity;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnKeyListener;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.widget.TextView;

public class MainActivity extends Activity {

    public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
          ListView myListView = (ListView)findViewById(R.id.myListView);
          final EditText myEditText = (EditText)findViewById(R.id.myEditText);
          final ArrayList<String> todoItems = new ArrayList<String>();
        final ArrayAdapter<String> aa;
        aa = new ArrayAdapter<String>(this,
                                      android.R.layout.simple_list_item_1,
                                      todoItems);
        myListView.setAdapter(aa);
           myEditText.setOnKeyListener(new OnKeyListener() {
             public boolean onKey(View v, int keyCode, KeyEvent event) {
               if (event.getAction() == KeyEvent.ACTION_DOWN)
                 if (keyCode == KeyEvent.KEYCODE_ENTER){
                   todoItems.add(0, myEditText.getText().toString());
                   aa.notifyDataSetChanged();
                   myEditText.setText("");
                   return true;
                 }
               return false;
        } });
        }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

public class TodoListItemView extends TextView {
      public TodoListItemView (Context context, AttributeSet ats, int ds) {
        super(context, ats, ds);
        init();
    }
      public TodoListItemView (Context context) {
        super(context);
        init();
    }
      public TodoListItemView (Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
      private void init() {
      }
      @Override
      public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
      }
    }

Answer 1

Eclipse is applying an optional (but very common) restriction. From the Java Language Specification, section 7.6 :

If and only if packages are stored in a file system (§7.2), the host system may choose to enforce the restriction that it is a compile-time error if a type is not found in a file under a name composed of the type name plus an extension (such as .java or .jav) if either of the following is true:

• The type is referred to by code in other compilation units of the package in which the type is declared.

• The type is declared public (and therefore is potentially accessible from code in other packages).

The fix is simple... one of:

• Make the class non-public
• Make it a nested type (eg within MainActivity )
• Put it in its own file with a name which matches the class's name

Unless you're going to nest it, I'd move it into its own file even if you also make it non-public.

Answer 2

Eclipse doesnt like you making a class unless it has its own file. Just make another file called TodoListItemView and put your class in there. Alternitavely, if you are only using the class in one activity, you could just make it private instead.

Thanks to Jon skeet I now know that you can also do this

If you want a public class, you can still make one by putting it inside of your activity

Answer 3

Different Classes need to be defined in their own files. Defining two classes in the same file will not work.