ImageView selector does not work

I am forming a tabhost like layout in my application with several ImageView. When I select on an item, the image will change. However, I tried to click on it, nothing happens! why??? activity_main.xml ``` <TableLayout android:id="@+id/main_tab_bar" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:stretchColumns="0,1,2,3,4"> <TableRow android:layout_width="match_parent" android:layout_height="wrap_content"> <ImageView android:id="@+id/news" android:clickable="true" android:focusable="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/main_tab_news_selector"/> <ImageView android:id="@+id/share" android:clickable="true" android:focusable="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/main_tab_share_selector"/> <ImageView android:id="@+id/camera" android:clickable="true" android:focusable="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/main_tab_camera_selector"/> <ImageView android:id="@+id/status" android:clickable="true" android:focusable="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/main_tab_status_selector"/> <ImageView android:id="@+id/others" android:clickable="true" android:focusable="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/main_tab_others_selector"/> </TableRow> </TableLayout> ``` main_tab_news_selector.xml (the other selectors are just similar) ``` <?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android" > <item android:drawable="@drawable/ic_action_time" android:state_focused="true" /> <item android:drawable="@drawable/ic_action_view_as_list" /> </selector> ```