addStatesFromChildren 和跑马灯

在Android中要显示跑马灯是比较容易的,只要设置2个属性就可以了:
android:singleLine="true"
android:ellipsize="marquee"

但 是要显示跑马灯该View必需是可以取得焦点的,只有在取得焦点的情况下跑马灯才会出现.
如果是组合View的情况下就有问题了, 如下一个组合View:

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --><? xml version="1.0" encoding="utf-8" ?>
< LinearLayout
   xmlns:android ="http://schemas.android.com/apk/res/android"
  android:orientation ="vertical"
  android:gravity ="center_vertical"
  android:background ="@drawable/f_background"
  android:layout_width ="fill_parent"
  android:focusable ="true"
  android:layout_height ="50px" >
   < TextView 
       android:id ="@+id/info_text"
      android:focusable ="true"
      android:layout_width ="fill_parent"
      android:layout_height ="wrap_content"
      android:text ="test marquee  .. "
      android:textColor ="@color/black"
      android:singleLine ="true"
      android:ellipsize ="marquee"
      android:marqueeRepeatLimit ="3"
      android:textSize ="18sp"
   />
   < TextView 
       android:id ="@+id/date_text"
      android:layout_width ="fill_parent"
      android:layout_height ="wrap_content"
      android:layout_gravity ="bottom"
      android:textColor ="@color/gray"
      android:text ="2010/05/28"
      android:textSize ="12sp"
   />
</ LinearLayout >

上面示例中2个TextView组合为一个View,由于设置了LinearLayout为focusable而TextView就没法取得焦点了,这样 这个TextView的跑马灯效果就显示不出来,就算你也设置TextView的 android:focusable= "true" 也是 没用的. 这个时候就要使用addStatesFromChildren 这个属性了,在LinearLayout中设置这个属性,然后设置TextView的focusable= "true" 就可以了.关于 addStatesFromChildren的说明:

Sets whether this ViewGroup's drawable states also include its children's drawable states.

可以正常显示的代码:


<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --><? xml version="1.0" encoding="utf-8" ?>
< LinearLayout
   xmlns:android ="http://schemas.android.com/apk/res/android"
  android:orientation ="vertical"
  android:gravity ="center_vertical"
  android:background ="@drawable/zixun_background"
  android:layout_width ="fill_parent"
  android:addStatesFromChildren ="true"
  android:layout_height ="50px" >
   < TextView 
       android:id ="@+id/info_text"
      android:focusable ="true"
      android:layout_width ="fill_parent"
      android:layout_height ="wrap_content"
      android:text =" "
      android:textColor ="@color/black"
      android:singleLine ="true"
      android:ellipsize ="marquee"
      android:marqueeRepeatLimit ="3"
      android:textSize ="18sp"
   />
   < TextView 
       android:id ="@+id/date_text"
      android:layout_width ="fill_parent"
      android:layout_height ="wrap_content"
      android:layout_gravity ="bottom"
      android:textColor ="@color/gray"
      android:text ="2010/05/28"
      android:textSize ="12sp"
   />
</ LinearLayout >