fill_parent设置一个顶部布局或控件强制性让它布满整个屏幕。

wrap_content布局指根据视图内部内容自动扩展以适应其大小。

1. wrap_content

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
 
    <Button
        android:id="@+id/btnButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button CJP"/>
 
</RelativeLayout>

2. fill_parent – width

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
 
    <Button
        android:id="@+id/btnButton1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Button CJP"/>
 
</RelativeLayout>

3. fill_parent – height

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
 
    <Button
        android:id="@+id/btnButton1"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:text="Button CJP"/>
 
</RelativeLayout>

4. fill_parent – width, height

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
 
    <Button
        android:id="@+id/btnButton1"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="Button CJP"/>
 
</RelativeLayout>

from :http://blog.csdn.net/jumping_android/article/details/7397991