[英]Why toString is not called for functions parameter?
I have and Enum for my intent Extras I like to use in my android app. 我有Enum和我想要在我的Android应用程序中使用的其他功能。 The type defenition is written like this:
类型定义是这样写的:
public enum Extras { TITLE, ID_USER } // ... and some more Extras
in my code I like to use the Enums like this: 在我的代码中,我喜欢这样使用枚举:
Intent i = new Intent();
i.putExtra( Extras.TITLE , "My Title String");
i.putExtra( Extras.ID_USER, 5);
And 和
String title = i.getStringExtra(Extras.TITLE);
int userId = i.getIntExtra(Extras.ID_USER, -1);
as I know enums have a toString method, my Enum Extras.TITLE
should be automatically be casted to the String "TITLE"
. 据我所知,枚举有一个toString方法,我的Enum
Extras.TITLE
应该自动转换为字符串"TITLE"
。
Its even working if I print it to screen like this 如果我将它打印到屏幕上,它甚至可以工作
System.out.println("Extra="+Extras.TITLE);
But for the Intent Methods I get the error message: 但是对于意图方法,我会收到错误消息:
The method putExtra(String, CharSequence) in the type Intent is not applicable for the arguments (Extras, CharSequence)
I could avoid this error if manually convert the enum to String like this: 如果将枚举手动转换为String,我可以避免此错误:
i.putExtra( Extras.TITLE.name() , "My Title String");
i.putExtra( Extras.TITLE.toString() , "My Title String");
But I like to know why to String issn`t called automatically when I pass my Enum as parameter to this method ? 但是我想知道为什么当我将Enum作为参数传递给此方法时,为什么会自动调用String issn`t吗?
Is there a way to to pass my Enums without calling toString() ? 有没有办法传递我的枚举而不调用toString()吗?
UPDATE: I tried to change my Enum to implement CharSequence interface. 更新:我试图更改我的枚举以实现CharSequence接口。 After this modification I can pass my Enums to methods which expect
CharSequence
parameters. 修改之后,我可以将Enums传递给需要
CharSequence
参数的方法。 But it is still incompatible with String methods. 但是它仍然与String方法不兼容。
public static enum Extras implements CharSequence { TITLE, ID_USER; // ... and some more Extras
@Override public char charAt( int index ) { return this.toString().charAt(index); }
@Override public int length() { return this.toString().length(); }
@Override public CharSequence subSequence( int start, int end ) { return this.toString().subSequence(start, end); }
}
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