Android手机输入法按键监听-dispatchKeyEvent
最近在项目开发中遇到一个关于手机输入键盘的坑，特来记录下。
应用场景：
项目中有一个界面是用viewpaper加三个fragment写的，其中viewpaper被我屏蔽了左右滑动，上面有三个点击按钮，点击他们可以切换页面（不要问我为什么这么写，因为你不知道需求有多么的操蛋）。每个fragment里面都有五六个竖着排列的edittext。只有一个fragment里面的edittext都填写了才让跳到下一个。大致效果图如下：
vc/ysLTFpaGjxuTL+8rWu/q/ycTc1rvT0MG9uPajrLK7zazK1rv6v8nE3LK70rvR+aGjtbG147v3y8S49rC0xaW1xMqxuvK74beiz9a958PmxNy5u8nPz8LX89PSzPjXqqOsxNy007Xa0ru49mZyYWdtZW50zPi1vbXatv649mZyYWdtZW50oaOho6Gj0rK+zcrHy7XF0LbPZWRpdHRleHTKx7fxzO7QtLXExdC2z87e0KfBy6GjvfvWubustq/Sss7e0KfBy6Oho6GjoTwvcD4NCjxwPjxzdHJvbmc+veK+9re9t6g8L3N0cm9uZz6jujxiciAvPg0K1tjQtEFjdGl2aXR51tC1xGRpc3BhdGNoS2V5RXZlbnTKwrz+yLu687bU06awtLz8vfjQ0LSmwO2jujwvcD4NCjxwcmUgY2xhc3M9"brush:java;">
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
// TODO Auto-generated method stub
if (event.getKeyCode() == KeyEvent.KEYCODE_DPAD_LEFT
|| event.getKeyCode() == KeyEvent.KEYCODE_DPAD_UP
|| event.getKeyCode() == KeyEvent.KEYCODE_DPAD_RIGHT
|| event.getKeyCode() == KeyEvent.KEYCODE_DPAD_DOWN) {
return true;
}
return super.dispatchKeyEvent(event);
}
KEYCODE_DPAD_LEFT （21）、KEYCODE_DPAD_UP （19）、KEYCODE_DPAD_RIGHT （22）、KEYCODE_DPAD_DOWN （20）这四个值对应的就是键盘上的四个按钮（左、上、右、下）的值。这里我的处理方案是直接给屏蔽了他的点击事件，相应的处理逻辑可以自己写。
这里还有一点要说下：
![这里写图片描述](/UpFiles/2017/5/26/041Ta5J-1.png "\")
如上图这里键盘也有自带的上下左右用于粘贴复制等操作，这四个键的keyCode跟上面四个的是一样的。不过有一点不同，就是当editText里面没有写东西的时候会检测不到按键。
再说下dispatchKeyEvent：
当键盘按下时的触发顺序 -> dispatchKeyEvent –> onUserInteraction –> onKeyDown
如果按下紧接着松开，则是触发两次。紧跟再触发–> dispatchKeyEvent –> onUserInteraction
–>onKeyUp
dispatchKeyEvent是做按键处理和分发的工作，如果你想要onKeyDown还可以接收到应该这样实现
public boolean dispatchKeyEvent(KeyEvent event){
return super.dispatchKeyEvent(event);
}
最后给大家附上键盘按键的code值：
/** Key code constant: Unknown key code. */
public static final int KEYCODE_UNKNOWN = 0;
/** Key code constant: Soft Left key.
* Usually situated below the display on phones and used as a multi-function
* feature key for selecting a software defined function shown on the bottom left
* of the display. */
public static final int KEYCODE_SOFT_LEFT = 1;
/** Key code constant: Soft Right key.
* Usually situated below the display on phones and used as a multi-function
* feature key for selecting a software defined function shown on the bottom right
* of the display. */
public static final int KEYCODE_SOFT_RIGHT = 2;
/** Key code constant: Home key.
* This key is handled by the framework and is never delivered to applications. */
public static final int KEYCODE_HOME = 3;
/** Key code constant: Back key. */
public static final int KEYCODE_BACK = 4;
/** Key code constant: Call key. */
public static final int KEYCODE_CALL = 5;
/** Key code constant: End Call key. */
public static final int KEYCODE_ENDCALL = 6;
/** Key code constant: '0' key. */
public static final int KEYCODE_0 = 7;
/** Key code constant: '1' key. */
public static final int KEYCODE_1 = 8;
/** Key code constant: '2' key. */
public static final int KEYCODE_2 = 9;
/** Key code constant: '3' key. */
public static final int KEYCODE_3 = 10;
/** Key code constant: '4' key. */
public static final int KEYCODE_4 = 11;
/** Key code constant: '5' key. */
public static final int KEYCODE_5 = 12;
/** Key code constant: '6' key. */
public static final int KEYCODE_6 = 13;
/** Key code constant: '7' key. */
public static final int KEYCODE_7 = 14;
/** Key code constant: '8' key. */
public static final int KEYCODE_8 = 15;
/** Key code constant: '9' key. */
public static final int KEYCODE_9 = 16;
/** Key code constant: '*' key. */
public static final int KEYCODE_STAR = 17;
/** Key code constant: '#' key. */
public static final int KEYCODE_POUND = 18;
/** Key code constant: Directional Pad Up key.
* May also be synthesized from trackball motions. */
public static final int KEYCODE_DPAD_UP = 19;
/** Key code constant: Directional Pad Down key.
* May also be synthesized from trackball motions. */
public static final int KEYCODE_DPAD_DOWN = 20;
/** Key code constant: Directional Pad Left key.
* May also be synthesized from trackball motions. */
public static final int KEYCODE_DPAD_LEFT = 21;
/** Key code constant: Directional Pad Right key.
* May also be synthesized from trackball motions. */
public static final int KEYCODE_DPAD_RIGHT = 22;
/** Key code constant: Directional Pad Center key.
* May also be synthesized from trackball motions. */
public static final int KEYCODE_DPAD_CENTER = 23;
/** Key code constant: Volume Up key.
* Adjusts the speaker volume up. */
public static final int KEYCODE_VOLUME_UP = 24;
/** Key code constant: Volume Down key.
* Adjusts the speaker volume down. */
public static final int KEYCODE_VOLUME_DOWN = 25;
/** Key code constant: Power key. */
public static final int KEYCODE_POWER = 26;
/** Key code constant: Camera key.
* Used to launch a camera application or take pictures. */
public static final int KEYCODE_CAMERA = 27;
/** Key code constant: Clear key. */
public static final int KEYCODE_CLEAR = 28;
/** Key code constant: 'A' key. */
public static final int KEYCODE_A = 29;
/** Key code constant: 'B' key. */
public static final int KEYCODE_B = 30;
/** Key code constant: 'C' key. */
public static final int KEYCODE_C = 31;
/** Key code constant: 'D' key. */
public static final int KEYCODE_D = 32;
/** Key code constant: 'E' key. */
public static final int KEYCODE_E = 33;
/** Key code constant: 'F' key. */
public static final int KEYCODE_F = 34;
/** Key code constant: 'G' key. */
public static final int KEYCODE_G = 35;
/** Key code constant: 'H' key. */
public static final int KEYCODE_H = 36;
/** Key code constant: 'I' key. */
public static final int KEYCODE_I = 37;
/** Key code constant: 'J' key. */
public static final int KEYCODE_J = 38;
/** Key code constant: 'K' key. */
public static final int KEYCODE_K = 39;
/** Key code constant: 'L' key. */
public static final int KEYCODE_L = 40;
/** Key code constant: 'M' key. */
public static final int KEYCODE_M = 41;
/** Key code constant: 'N' key. */
public static fin