<TableRow>
<TextView android:text="URL:" />
<EditText
android:id="@+id/entry"
android:layout_span="3"/>
</TableRow>
In this XML layout fragment, the field spans three columns.
Ordinarily, widgets are put into the first available column. In the preceding fragment, the label would go in the first column (column 0, as columns are counted starting from 0), and the field would go into a spanned set of three columns (columns 1 through 3). However, you can put a widget into a different column via the android:layout_column property, specifying the 0-based column the widget belongs to:
<TableRow>
<Button
android:id="@+id/cancel"
android:layout_column="2"
android:text="Cancel" />
<Button android:id="@+id/ok" android:text="OK" />
</TableRow>
In this XML layout fragment, the Cancel button goes in the third column (column 2). The OK button then goes into the next available column, which is the fourth column.
Normally, TableLayout contains only TableRow elements as immediate children. However, it is possible to put other widgets in between rows. For those widgets, TableLayout behaves a bit like LinearLayout with vertical orientation. The widgets automatically have their width set to fill_parent, so they will fill the same space that the longest row does.
One pattern for this is to use a plain View as a divider (e.g., <View android:layout_height="2px" android:background="#0000FF" /> as a two-pixel-high blue bar across the width of the table).
By default, each column will be sized according to the “natural” size of the widest widget in that column (taking spanned columns into account). Sometimes, though, that does not work out very well, and you need more control over column behavior.
You can place an android:stretchColumns property on the TableLayout. The value should be a single column number (again, 0-based) or a comma-delimited list of column numbers. Those columns will be stretched to take up any available space on the row. This helps if your content is narrower than the available space.
Conversely, you can place an android:shrinkColumns property on the TableLayout. Again, this should be a single column number or a comma-delimited list of column numbers. The columns listed in this property will try to word-wrap their contents to reduce the effective width of the column; by default, widgets are not word-wrapped. This helps if you have columns with potentially wordy content that might cause some columns to be pushed off the right side of the screen.
You can also leverage an android:collapseColumns property on the TableLayout, again with a column number or a comma-delimited list of column numbers. These columns will start out “collapsed,” meaning they will be part of the table information but will be invisible. Programmatically, you can collapse and un-collapse columns by calling setColumnCollapsed() on the TableLayout. You might use this to allow users to control which columns are of importance to them and should be shown, versus which ones are less important and can be hidden.
You can also control stretching and shrinking at runtime via setColumnStretchable() and setColumnShrinkable().
TableLayout Example
The XML layout fragments shown previously, when combined, give us a TableLayout rendition of the “form” we created for RelativeLayout, with the addition of a divider line between the label/field and the two buttons (found in the Containers/Table demo in the Source Code area of http://apress.com):
<?xml version="1.0" encoding="utf-8"?>
<TableLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:stretchColumns="1">
<TableRow>
<TextView
android:text="URL:" />
<EditText android:id="@+id/entry"
android:layout_span="3"/>
</TableRow>
<View
android:layout_height="2px"
android:background="#0000FF" />
<TableRow>
<Button android:id="@+id/cancel"
android:layout_column="2"
android:text="Cancel" />
<Button android:id="@+id/ok"
android:text="OK" />
</TableRow>
</TableLayout>
When compiled against the generated Java code and run on the emulator, we get the result shown in Figure 7-7.
Figure 7-7. The TableLayoutDemo sample application
Scrollwork
Phone screens tend to be small, which requires developers to use some tricks to present a lot of information in the limited available space. One trick for doing this is to use scrolling, so only part of the information is visible at one time, and the rest is available via scrolling up or down.
ScrollView is a container that provides scrolling for its contents. You can take a layout that might be too big for some screens, wrap it in a ScrollView, and still use your existing layout logic. It just so happens that the user can see only part of your layout at one time; the rest is available via scrolling.
For example, here is a ScrollView used in an XML layout file (from the Containers/Scroll demo in the Source Code area of http://apress.com):
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TableLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:stretchColumns="0">
<TableRow>
<View
android:layout_height="80px"
android:background="#000000"/>
<TextView android:text="#000000"
android:paddingLeft="4px"
android:layout_gravity="center_vertical" />
</TableRow>
<TableRow>
<View
android:layout_height="80px"
android:background="#440000" />