android.inputmethodservice.KeyboardView.OnKeyboardActionListener
接口OnKeyboardActionListener在KeyboardView中定义，用于监听虚拟键盘事件。
在接口OnKeyboardActionListener中声明8个抽象方法
1. void onPress(int primaryCode)
Called when the user presses a key. This is sent before the onKey is called. For keys that repeat, this is only called once.
Parameters:
- primaryCode the unicode of the key being pressed. If the touch is not on a valid key, the value will be zero.
2. void onRelease(int primaryCode)
Called when the user releases a key. This is sent after the onKey is called. For keys that repeat, this is only called once.
Parameters:
- primaryCode the code of the key that was released
3. void onKey(int primaryCode, int[] keyCodes)
Send a key press to the listener.
Parameters:
- primaryCode this is the key that was pressed
- keyCodes the codes for all the possible alternative keys with the primary code being the first. If the primary key code is a single character such as an alphabet or number or symbol, the alternatives will include other characters that may be on the same key or adjacent keys. These codes are useful to correct for accidental presses of a key adjacent to the intended key.
4. void onText(CharSequence text)
Sends a sequence of characters to the listener.
Parameters:
- text the sequence of characters to be displayed.
5. void swipeLeft()
Called when the user quickly moves the finger from right to left.
6. void swipeRight()
Called when the user quickly moves the finger from left to right.
7. void swipeDown()
Called when the user quickly moves the finger from up to down.
8. void swipeUp()
Called when the user quickly moves the finger from down to up.