Android之输入法开发简单说明

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http://news.wangmeng.cn/detailNews/2616-android-development-of-a-simple-description-of-the-input

创建一个输入法，必须继承android.inputmethodservice.InputMethodService，它作为一个服务，监听所有EditText的事件。

看一个AndroidManifest.xml文件的示例:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.fastinput">
 
<application android:label="@string/app_label">
 
<!-- Declares the input method service -->
<service android:name="FastInputIME"
android:label="@string/fast_input_label"
android:permission="android.permission.BIND_INPUT_METHOD">
<intent-filter>
<action android:name="android.view.InputMethod" />
</intent-filter>
<meta-data android:name="android.view.im" android:resource="@xml/method" />
</service>
 
<!-- Optional activities. A good idea to have some user settings. -->
<activity android:name="FastInputIMESettings" android:label="@string/fast_input_settings">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
</intent-filter>
</activity>
</application>
</manifest>

整个输入法的生命周期如下图所示：

Input View
软键盘的主界面，在InputMethodService.onCreateInputView() 初始化.
Candidates View
This is where potential word corrections or completions are presented to the user for selection. Again, this may or may not be relevant to your input method and you can return null from calls to InputMethodService.onCreateCandidatesView() , which is the default behavior.

InputMethodService.onStartInputView() 输入法开始函数。
(EditorInfo.inputType & EditorInfo.TYPE_CLASS_MASK ) can be one of many different values, including:
TYPE_CLASS_NUMBER
TYPE_CLASS_DATETIME
TYPE_CLASS_PHONE
TYPE_CLASS_TEXT

See android.text.InputType for more details.
EditorInfo.inputType can contain other masked bits that indicate the class variation and other flags. For example, TYPE_TEXT_VARIATION_PASSWORD or TYPE_TEXT_VARIATION_URI or TYPE_TEXT_FLAG_AUTO_COMPLETE .
Password fields
Pay specific attention when sending text to password fields. Make sure that the password is not visible within your UI - in neither the input view nor the candidates view. And do not save the password anywhere without explicitly informing the user.
Landscape vs. portrait

The UI needs to be able to scale between landscape and portrait orientations. In non-fullscreen IME mode, leave sufficient space for the application to show the text field and any associated context. Preferably, no more than half the screen should be occupied by the IME. In fullscreen IME mode this is not an issue.
Sending text to the application

There are two ways to send text to the application. You can either send individual key events or you can edit the text around the cursor in the application's text field.
To send a key event, you can simply construct KeyEvent objects and call InputConnection.sendKeyEvent(). Here are some examples:

InputConnection ic = getCurrentInputConnection();
long eventTime = SystemClock.uptimeMillis();
ic.sendKeyEvent(new KeyEvent(eventTime, eventTime,
KeyEvent.ACTION_DOWN, keyEventCode, 0, 0, 0, 0,
KeyEvent.FLAG_SOFT_KEYBOARD|KeyEvent.FLAG_KEEP_TOUCH_MODE));
ic.sendKeyEvent(new KeyEvent(SystemClock.uptimeMillis(), eventTime,
KeyEvent.ACTION_UP, keyEventCode, 0, 0, 0, 0,
KeyEvent.FLAG_SOFT_KEYBOARD|KeyEvent.FLAG_KEEP_TOUCH_MODE));

Or use the convenience method:

1.InputMethodService.sendDownUpKeyEvents(keyEventCode);

Note : It is recommended to use the above method for certain fields such as phone number fields because of filters that may be applied to the text after each key press. Return key and delete key should also be sent as raw key events for certain input types, as applications may be watching for specific key events in order to perform an action.
When editing text in a text field, some of the more useful methods on android.view.inputmethod.InputConnection are:
getTextBeforeCursor()
getTextAfterCursor()
deleteSurroundingText()
commitText()
For example, let's say the text "Fell" is to the left of the cursor. And you want to replace it with "Hello!":

InputConnection ic = getCurrentInputConnection();
ic.deleteSurroundingText(4, 0);
ic.commitText("Hello", 1);
ic.commitText("!", 1);

Composing text before committing
If your input method does some kind of text prediction or requires multiple steps to compose a word or glyph, you can show the progress in the text field until the user commits the word and then you can replace the partial composition with the completed text. The text that is being composed will be highlighted in the text field in some fashion, such as an underline.

InputConnection ic = getCurrentInputConnection();
ic.setComposingText("Composi", 1);
...
ic.setComposingText("Composin", 1);
...
ic.commitText("Composing ", 1);

Intercepting hard key events

Even though the input method window doesn't have explicit focus, it receives hard key events first and can choose to consume them or forward them along to the application. For instance, you may want to consume the directional keys to navigate within your UI for candidate selection during composition. Or you may want to trap the back key to dismiss any popups originating from the input method window. To intercept hard keys, override InputMethodService.onKeyDown() and InputMethodService.onKeyUp(). Remember to call super.onKey * if you don't want to consume a certain key yourself.
Other considerations

Provide a way for the user to easily bring up any associated settings directly from the input method UI
Provide a way for the user to switch to a different input method (multiple input methods may be installed) directly from the input method UI.
Bring up the UI quickly - preload or lazy-load any large resources so that the user sees the input method quickly on tapping on a text field. And cache any resources and views for subsequent invocations of the input method.
On the flip side, any large memory allocations should be released soon after the input method window is hidden so that applications can have sufficient memory to run. Consider using a delayed message to release resources if the input method is in a hidden state for a few seconds.
Make sure that most common characters can be entered using the input method, as users may use punctuation in passwords or user names and they shouldn't be stuck in a situation where they can't enter a certain character in order to gain access into a password-locked device.
Samples

For a real world example, with support for multiple input types and text prediction, see LatinIME source code . The Android 1.5 SDK also includes a SoftKeyboard sample as well