ScrollVie滚动条

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <!-- 滚动条 -->
    <!-- 每个ScrollView控件里面只能包含一个子元素、如果有多个子元素可用现行布局包裹起来 -->

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <LinearLayout
            android:id="@+id/linear"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:gravity="center_horizontal">
<!-- 图片控件 -->
            <ImageView
                android:id="@+id/img"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:src="@drawable/a" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/hello_world"
                android:textSize="30sp" />


        </LinearLayout>
    </ScrollView>

</LinearLayout>