为什么在Android设置SettingsActivity中使用静态内部类

Question

当我在Android中阅读设置源代码时，我发现了这段代码

public class Settings extends SettingsActivity {
    /*
    * Settings subclasses for launching independently.
    */
    public static class BluetoothSettingsActivity extends SettingsActivity { /* empty */ }
    public static class WirelessSettingsActivity extends SettingsActivity { /* empty */ }
    public static class SimSettingsActivity extends SettingsActivity { /* empty */ }
    public static class TetherSettingsActivity extends SettingsActivity { /* empty */ }
    ...
}

任何人都可以告诉我这样做有什么好处？我们可以直接使用SettingsActivity吗？

Answer 1

在大多数情况下，它只是一种命名空间技术。这些示例在功能上是相同的，它们对public class A { // class A public static class B { // class A.B } } 只有不同的用法。

public class A { // class A

}

public class B { // class B

}

public static

new Settings.BluetoothSettingsActivity() 内部类的行为与未嵌套的类完全相同。您必须首先给外部类访问内部类，例如：

static

如果没有指定`chef1.example.com ChefVault::Exceptions::KeysNotFound` `chef1.example.com -----------------------------------` `chef1.example.com myusers/testuser_keys_keys could not be found` `chef1.example.com Cookbook Trace:` `chef1.example.com Relevant File Content: chef1.example.com ---------------------- chef1.example.com /var/chef/cache/cookbooks/user_management/recipes/default.rb: chef1.example.com chef1.example.com 30: require 'chef-vault' chef1.example.com 31: chef1.example.com 32: if node['user_management']['use_databag'] == true then chef1.example.com 33: users = data_bag(node['user_management']['databag_name']) chef1.example.com 34: sudoer_users = Array.new() chef1.example.com 35: users.each do |id| chef1.example.com 36:#user = data_bag_item(node['user_management']['databag_name'], id) chef1.example.com 37>> user =ChefVault::Item.load(node['user_management']['databag_name'], id) chef1.example.com 38: user_management user['id'] do chef1.example.com 39: comment user['comment'] unless user['comment'].nil? chef1.example.com 40: create_home user['create_home'] chef1.example.com 41: shell user['shell'] unless user['shell'].nil? chef1.example.com 42: password user['password'] unless user['password'].nil? chef1.example.com 43: uid user['uid'] unless user['uid'].nil? chef1.example.com 44: gid user['gid'] unless user['gid'].nil? chef1.example.com 45: ssh_keys user['ssh_keys'] unless user['ssh_keys'].nil? chef1.example.com 46:delete_home_when_remove user['delete_home_when_remove'] unless user['delete_home_when_remove'].nil?` ，则会有很大的不同。请参阅this question。