实例化xml文件中的内部类(首选项) [英] Instantiating an inner class (Preference) in xml file

问题描述

当您要访问某些layout.xml文件中的自定义视图时，有两种选择:

When you want to access a custom view in some layout.xml file, you have two options:

1. 该视图位于其自己的类中.然后，您执行<package.name.MyView android:layout_width= ... />
2. 该视图是一个内部类:<view class="package.name.OuterClass$MyView" android:layout_width= ... />

1. The view is in it's own class. Then you do <package.name.MyView android:layout_width= ... />
2. The view is an inner class: <view class="package.name.OuterClass$MyView" android:layout_width= ... />

现在，我想在<PreferenceScreen>中做同样的事情.第一种方法很好用，但是我想将所有自定义的Preference类放到我的PreferenceActivity中.我尝试了<Preference class="package.name.OuterClass$MyPreference" ... />(也使用'.'而不是'$')以及<package.name.OuterClass.MyPreference ... />，但是都失败了.

Now I want to do the same thing inside a <PreferenceScreen>. The first way works well, but I would like to put all the custom Preference classes together in my PreferenceActivity. I tried <Preference class="package.name.OuterClass$MyPreference" ... /> (also with '.' instead of '$') as well as <package.name.OuterClass.MyPreference ... />, but both failed.

有人有主意吗?

推荐答案

在处理Views膨胀时，LayoutInflater查找视图"->类"情况:

When dealing with Views inflating, LayoutInflater looks for a "view" -> "class" case:

View createViewFromTag(View parent, String name, AttributeSet attrs) {
    if (name.equals("view")) {
        name = attrs.getAttributeValue(null, "class");
    } ...

首选项的PreferenceInflater没有，因此适用于类"的情况.

Preference's PreferenceInflater doesn't, so that is for the "class" case.

它在其createItem()方法中使用了反射，这可能就是第一种情况对您有用的原因.

It uses reflection in its createItem() method and that's probably why the first case works for you.

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