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Most Android developers have used the class android.widget.TextView somewhere in their UIs.  TextView puts some text on the screen, to label another component or to convey something to the user.   If you want the user to input or edit the text, there’s an XML attribute that you can set like this, in the layout.xml file:

<TextView  
android:editable="true"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/init_value"
android:id="@+id/my_tv1"
/>

 The editable attribute isn’t enough, by itself, to support the user typing into a TextView. You also need to connect a real or virtual keyboard (an “input method”), and add a KeyListener to collect the user keystrokes.  (If you’re wondering about that “match_parent” in the xml, that value replaced “fill_parent” from API level 8, in a rare (but laudible) attempt at purposeful name improvement in the Android API).

For ready-to-go editable fields, most developers use the class android.widget.EditText .  EditText is a subclass of TextView, with all the editable settings and customizations already correctly initialized, and ready for use.   Your layout file will then contain an element like this:

<EditText  
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/init_value"
android:id="@+id/my_et1"
/>

The base class, android.widget.TextView, is a rather formidable chunk of code, weighing in at more than 7300 lines of code.   Quoting from the developer docs, class EditText is intended as “a thin veneer over TextView that configures it to be editable.”  EditText is about 100 lines of code, with 4 or 5 overriding methods forcing particular settings, and another 4 or 5 convenience methods that help with editing (selecting text, highlighting it, and so on).   

There’s a warning in the comments at the top of EditText saying “Don’t do anything here that a TextView with a KeyListener and a cursor movement method wouldn’t do.” In other words, if you update or extend EditText, keep it a simple subclass.  Radical changes belong somewhere else. EditText has a subclass, android.widget.AutoCompleteTextView, that offers string completion suggestions automatically from a dictionary array, as the user enters characters.

Set the inputType
There is an XML attribute of “inputType” which can be used with TextView and its subclasses to limit the kind of data the user can enter in a text field.  The input method uses the inputType value to decide how to let the user enter text.  The method does it by adding a subclass of android.text.InputFilter to the editable object to limit the characters that the object can hold.  

Phone

For example, if you’ve specified the EditText field holds a phone number, then only digits 0-9, +, -, space, and a few other characters are valid in what the user types.  Your XML in the layout file will look like:

<EditText  
android:inputType="phone"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/init_value"
android:id="@+id/my_et1"
/>

The resulting EditText field will look like:
   

Number

The “number” inputType limits the user to inputting a single number, with the resulting keyboard shown below.

<EditText  
android:inputType="number"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/init_value"
android:id="@+id/my_et1"
/>

When you use the “number” inputType, the default Android input method simply displays the numeric page, rather than the alphabetic page, of the standard virtual keyboard.

Time

The “time” inputType is for restricting the input to time strings.  It comes up with the regular keypad, but it will only accept characters that make sense as a time string.   An example screenshot is below the sample XML.

<EditText  
android:inputType="time"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/init_value"
android:id="@+id/my_et1"
/>

What Else?
There are about 30 different values that you can give to an inputType attribute, to modify what the user may type into a TextView or EditView.  Some of the values can sensibly be OR’d together, like this example from the IM app:
       android:inputType="textShortMessage|textAutoCorrect|textCapSentences|textMultiLine"

The complete list of inputTypes is here. 

Changing the appearance, layout, or other visuals of a View (such as the color, size and typeface of the font within it) is known as styling.  Unlike the examples here, when using a style, all the attribute settings are made in a separate XML file. You can also apply a style to an entire Fragment, Activity or Application - a technique known as themeing.  Please return to this blog soon for a future tutorial on Styling and Themeing in Android.

Peter van der Linden

Android Technology Evangelist