Chapter 11

The Input Method Framework

Android 1.5 introduced the input method framework (IMF), which is commonly referred to as soft keyboards. However, this term is not necessarily accurate, as IMF could be used for handwriting recognition or other means of accepting text input via the screen.

Keyboards, Hard and Soft

Some Android devices have a hardware keyboard that is visible some of the time (when it is slid out). A few Android devices have a hardware keyboard that is always visible (so-called “bar” or “slab” phones). Most Android devices, though, have no hardware keyboard at all. The IMF handles all of these scenarios.

In short, if there is no hardware keyboard, an input method editor (IME) will be available to the user when they tap an enabled EditText widget. If the default functionality of the IME is what you want to offer, you don't need to make any code changes to your application. Fortunately, Android is fairly smart about guessing what you want, so you may simply need to test with the IME and make no specific code changes.

But the IME may not quite behave how you would like it to for your application. For example, in the Basic/Field sample project, the FieldDemo activity has the IME overlaying the multiple-line EditText, as shown in Figure 11–1. It would be nice to have more control over how this appears, and to be able to control other behavior of the IME. Fortunately, the IMF as a whole gives you many options for this, as described in this chapter.

Figure 11–1. The input method editor, as seen in the FieldDemo sample application

Tailored to Your Needs

Android 1.1 and earlier offered many attributes on EditText widgets to control their style of input, such as android:password to indicate a field should be for password entry (shrouding the password keystrokes from prying eyes). Starting in Android 1.5, with the IMF, many of these attributes have been combined into a single android:inputType attribute.

The android:inputType attribute takes a class plus modifiers, in a pipe-delimited list (where | is the pipe character). The class generally describes what the user is allowed to input, and this determines the basic set of keys available on the soft keyboard. The available classes are as follows:

• text (the default)
• number
• phone
• datetime
• date
• time

Many of these classes offer one or more modifiers to further refine what the user will be allowed to enter. To get a better understanding of how these modifiers work, take a look at the res/layout/main.xml file from the InputMethod/IMEDemo1 project:

This shows a TableLayout containing five rows, each demonstrating a slightly different flavor of EditText:

• The first row has no attributes at all on the EditText, meaning you get a plain text-entry field.
• The second row has android:inputType = "text|textEmailAddress", meaning it is a text-entry field that specifically seeks an e-mail address.
• The third row allows for signed decimal numeric input, via android:inputType = "number|numberSigned|numberDecimal".
• The fourth row is set up to allow for data entry of a date (android:inputType = "date").
• The last row allows for multiline input with autocorrection of probable spelling errors (android:inputType = "text|textMultiLine|textAutoCorrect").

The class and modifiers tailor the keyboard. For example, a plain text-entry field results in a plain soft keyboard, as shown in Figure 11–2.

Figure 11–2. A standard input method editor (a.k.a. soft keyboard)

An e-mail address field might put the @ symbol on the soft keyboard, at the cost of a smaller spacebar, as shown in Figure 11–3.

Figure 11–3. The input method editor for e-mail addresses

Note that this behavior is specific to the IME. Some editors might put the @ symbol on the primary keyboard for an e-mail field. Some might put a .com button on the primary keyboard. Some might not react at all. It is up to the implementation of the IME—all you can do is supply the hint.

Number and date fields restrict the keys to numeric keys, plus a set of symbols that may or may not be valid on a given field, as shown in Figure 11–4.

Figure 11–4. The input method editor for signed decimal numbers

These are just a few examples of the possible IMEs. By choosing the appropriate android:inputType, you can give users a soft keyboard that best suits the type of data they should be entering.

Tell Android Where It Can Go

You may have noticed a subtle difference between the IME shown in Figure 11–2 and the IME shown in Figure 11–3, beyond the addition of the @ key. The lower-right corner of the soft keyboard in Figure 11–3 has a Next button, whereas the one in Figure 11–2 has a newline button. This points out two things:

• EditText widgets are multiline by default if you do not specify android:inputType.
• You can control what goes on with that lower-right button, called the accessory button.

By default, on an EditText widget where you have specified android:inputType, the accessory button will be Next, moving you to the next EditText widget in sequence, or Done, if you are on the last EditText widget on the screen. You can manually stipulate what the accessory button will be labeled via the android:imeOptions attribute. For example, in the res/layout/main.xml file from InputMethod/IMEDemo2, you will see an augmented version of the previous example, where two input fields specify what their accessory button should look like:

Here, we attach a Send action to the accessory button for the e-mail address (android:imeOptions = "actionSend"), and the Done action on the middle field (android:imeOptions = "actionDone").

By default, Next moves the focus to the next EditText and Done closes the IME. However, for those actions, or for any others like Send, you can use setOnEditorActionListener() on EditText (technically, on the TextView superclass) to get control when the accessory button is clicked or the user presses the Enter key. You are provided with a flag indicating the desired action (e.g., IME_ACTION_SEND), and you can then do something to handle that request (e.g., send an e-mail to the supplied e-mail address).

Fitting In

Notice that the IMEDemo2 layout shown in the preceding section has another difference from its IMEDemo1 predecessor: the use of a ScrollView container wrapping the TableLayout. This ties into another level of control you have over the IMEs: what happens to your activity's own layout when the IME appears. There are three possibilities, depending on circumstances:

• Android can “pan” your activity, effectively sliding the whole layout up to accommodate the IME, or overlaying your layout, depending on whether the EditText being edited is at the top or bottom. This has the effect of hiding some portion of your UI.
• Android can resize your activity, effectively causing it to shrink to a smaller screen dimension, allowing the IME to sit below the activity itself. This is great when the layout can readily be shrunk (e.g., it is dominated by a list or multiline input field that does not need the whole screen to be functional).
• Android may display the IME full-screen, obscuring your entire activity. This allows for a bigger keyboard and generally easier data entry.    

Android controls the full-screen option using its historic defaults. And, by default, Android will choose between pan and resize modes depending on what your layout looks like. If you want to specifically choose between pan and resize, you can do so via an android:windowSoftInputMode attribute on the <activity> element in your AndroidManifest.xml file. For example, here is the manifest from IMEDemo2:

Because we specified resize, Android will shrink our layout to accommodate the IME. With the ScrollView in place, this means the scroll bar will appear as needed, as shown in Figure 11–5.

Figure 11–5. The shrunken, scrollable layout

You can control Android's behavior to maximize screen real-estate by using the additional methods introduced in Honeycomb, and refined in Ice Cream Sandwich. Use the Java method setSystemUiVisibility() with the STATUS_BAR_HIDDEN option to hide the System Bar and allow even larger full-screen modes, or use the method setDimAmount() to tweak the brightness of the home buttons to remove distractions from your regularly resized full-screen layout.

Jane, Stop This Crazy Thing!

Sometimes, you need the IME to just go away. For example, if you make the accessory button a Search button, the IME won't be hidden automatically when the user taps that button, whereas you may want it to be hidden. To hide the IME, you need to make a call to the InputMethodManager, a system service that controls these IMEs:

(In the preceding line, fld is the EditText whose IME you want to hide.)

This will always close the designated IME. However, bear in mind that there are two ways a user can open the IME in the first place:

• If the user's device does not have a hardware keyboard exposed, and the user taps the EditText, the IME should appear.
• If the user previously dismissed the IME or is using the IME for a widget that does not normally pop one up (e.g., ListView), and the user presses the Menu button, the IME should appear.

If you want to close the IME only for the first scenario, but not the second, use InputMethodManager.HIDE_IMPLICIT_ONLY as a flag for the second parameter to your call to hideSoftInputFromWindow(), instead of the 0 shown in the previous example.