Key event handling process

I'd like to know how the key event is handled in Android开发者_开发问答 platform. From 'when user type key 'a' on software keyboard', To 'view draw the character 'a' on itself'.

Probably, the key event is generated by IME, And it will be sent to parent view, Finally, view(such as EditText) displays chracters.

Please somebody explains about these entire key event handling process.

Take a look at this article: http://developer.android.com/resources/articles/creating-input-method.html

Basically, you can either manually send KeyEvents or you can manually edit and commit text around the cursor in the application's Input View.

These are all done via your IME's InputConnection.

OnKeyListener and OnKeyDown do not get called, as you have discovered, when using a software keyboard. They only get called when using a hardware keyboard, which many Android devices don't even have.

I assume what you are trying to do is capture key events as they are occurring in an EditText area. Your best bet in this case, in order to handle both software keyboard input and hardware keyboard input, is to register a TextWatcher via the addTextChangedListener() method.

Note that on phones with Android 2.1 and later, such as the Nexus One, people have the option of using speech recognition to input text into your EditText instead of typing the text. When they do that you may get full words, or even full sentences, entered all at once. So you need to check the entire contents of the EditText field when there is a change to the contents.