Android access attribute reference

In the Android resources xml to reference the value of an attribute for a theme you use the question-mark (?) instead of at (@). Such as ListViewCustomStyle below:

 <ListView 
     android:id="@+id/MainScreenListView" 
     android:layout_width="fill_parent" 开发者_如何学C
     android:layout_height="wrap_content"
     style="?ListViewCustomStyle"/>

How can I use the value of the ListViewCustomStyle in code? If I try it the normal way i.e.

com.myapp.R.attr.ListViewCustomStyle

Then the code crashes. Is there a special way to access this since it is a reference to an item and not an actual item?

It might just be crashing because you wrote ListRowCustomStyle there, and ListViewCustomStyle in your xml.

The way I do this is to have the tag style="@style/my_button" for example (with no android: preceding it). Then you can define your style in the values/styles.xml file, e.g.

    <?xml version="1.0" encoding="utf-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <style name="my_button" parent="@android:style/Widget.Button">
        <item name="android:gravity">center_vertical|center_horizontal</item>
        <item name="android:textColor">#FFFFFFFF</item>
    ...
       </style>
</resources>

You can access the style in code by using the id R.style.my_button

I believe in the xml you wanted to write

style="@style/ListViewCustomStyle"

Anyway, how to use it in code?

Last time I check, it was impossible :(

I did it with a trick:

1. create a layout file as the example that follows:

    <Button
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    style="@style/MyCustomStyle"/>
   

2. when you want to add an object with your custom style in code, you have to inflate it, using this layout you just created:

:

LayoutInflater inflater = LayoutInflater.from(this); // this = activity or context
Button button = (Button) inflater.inflate(R.layout.myButtonWithMyStyle, null); //use the same layout file as above
button.setText("It works!");
myView.addView(button);

This is considerably slower than creating a Button in code. It may be a problem if you create hundreads of Views at the same time using this method. Less than that I think you can handle it.