就这样写:

 android:divider="?android:dividerHorizontal"
 android:showDividers="middle"

完整的例子:

<LinearLayout
        android:id="@+id/llTipInformation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvServiceRating"
        android:orientation="horizontal"
        android:divider="?android:dividerHorizontal"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:showDividers="middle">

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center"
            android:text="@string/main.msg.tippercent"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:textColor="@color/colorWhite"
            android:layout_marginTop="@dimen/activity_vertical_margin"/>
        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center"
            android:text="@string/main.msg.tiptotal"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:textColor="@color/colorWhite"
            android:layout_marginTop="@dimen/activity_vertical_margin"/>

</LinearLayout>

添加此视图;在你的textview之间画一个分隔符

<View
    android:layout_width="match_parent"
    android:layout_height="1dp"
    android:background="#000000" />

<layer-list xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<item
    android:bottom="0dp"
    android:left="-2dp"
    android:right="-2dp"
    android:top="-2dp">
    <shape android:shape="rectangle">
        <stroke
            android:width="1dp"
            android:color="@color/divider" />
    </shape>
</item>

要完成Camille Sévigny回答，您可以另外定义自己的线形状，例如自定义线的颜色。

在可绘制目录中定义一个xml形状。line_horizontal.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto" android:shape="line">
    <stroke android:width="2dp" android:color="@android:color/holo_blue_dark" />
    <size android:width="5dp" />
</shape>

在你的布局中使用这一行和你想要的属性:

    <ImageView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="2dp"
        android:paddingLeft="5dp"
        android:paddingRight="5dp"
        android:paddingTop="2dp"
        android:src="@drawable/line_horizontal" />

我通常使用这样的代码:

<ImageView
    android:id="@+id/imageView2"
    android:layout_width="match_parent"
    android:layout_height="1dp"
    android:layout_alignParentLeft="true"
    android:layout_marginLeft="10dp"
    android:layout_marginRight="10dp"
    android:layout_marginTop="10dp"
    android:background="#aa000000" />

如果你在你的布局中有一个对象，你想在下面设置line，使用ImageView中的这个属性:

android:layout_below="@+id/textBox1"

运行时版本:

View dividerView = new View(getContext());
LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
    ViewGroup.LayoutParams.FILL_PARENT, UIUtils.dpToPix(getContext(), 1));
dividerView.setLayoutParams(lp);

TypedArray array = getContext().getTheme()
    .obtainStyledAttributes(new int[] {android.R.attr.listDivider});
Drawable draw = array.getDrawable(0);       
array.recycle();

dividerView.setBackgroundDrawable(draw);
mParentLayout.addView(dividerView);