我想知道在按钮上单击背景颜色是如何变化的，它发生的时间超过了按钮的大小。有人能告诉我背景颜色是从哪里来的吗？在 android api 4.1 中，在 path: Android API-res-layout-log_text_box_1.xml文件看起来像这样。
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-->
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/log_text_box_1_add_text"/>
<com.example.android.apis.text.LogTextBox
android:id="@+id/text"
android:background="@drawable/box"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:scrollbars="vertical"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/log_text_box_1_do_nothing_text"/>
</LinearLayout>
