android - 如何使用它创建一个扩展 Application 并覆盖其 onCreate() 方法的类

Question

错误:

Application cannot be resolved to a type

SharedPreferences cannot be resolved to a type`

the method override must override or implement a super type method

Multiple markers at this line

PreferenceManager cannot be resolved

程序:

 package com.su.vapour;

public class Common extends Application {  

    public static String[] email_arr;
    private static SharedPreferences prefs;

    @Override
    public void onCreate() {
        super.onCreate();
        prefs = PreferenceManager.getDefaultSharedPreferences(this);

        List<String> emailList = getEmailList();
        email_arr = emailList.toArray(new String[emailList.size()]);
    }

    private List<String> getEmailList() {
        List<String> lst = new ArrayList<String>();
        Account[] accounts = AccountManager.get(this).getAccounts();
        for (Account account : accounts) {
            if (Patterns.EMAIL_ADDRESS.matcher(account.name).matches()) {
                lst.add(account.name);
            }
        }
        return lst;
    }  
}

Answer 1

您需要添加import您在此 Java 文件中引用的类和接口(interface)的语句，例如 android.app.Application和 android.content.SharedPreferences .
import语句是一个相当基本的 Java 概念。我强烈建议你去学习 Java，尤其是 key areas Android应用程序开发所需的。