andriod 手机按键检测事件 onKeyDown() 简述

函数原型：

public boolean onKeyDown(int keyCode, KeyEvent event);

第一个参数是用户按下键时，当前所接收到的按键代号；

第二个参数是按键事件的对象。

使用方法：

如果要使用这个方法。直接在主 acivity 中重写即可，一般使用开关语句 switch 来把keyCode 和 （event.按键类型） 对比来执行对应的操作。

下面我们来看下event 的按键属性都有哪些。

在上面的函数中，按住control 加 鼠标左键点击 KeyEvent，就可以点进去看到很多东西。

 public class KeyEvent extends InputEvent implements Parcelable {
     /** 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 final int KEYCODE_N               = 42;
     /** Key code constant: 'O' key. */
     public static final int KEYCODE_O               = 43;
     /** Key code constant: 'P' key. */
     public static final int KEYCODE_P               = 44;
     /** Key code constant: 'Q' key. */
     public static final int KEYCODE_Q               = 45;
     /** Key code constant: 'R' key. */
     public static final int KEYCODE_R               = 46;
     /** Key code constant: 'S' key. */
     public static final int KEYCODE_S               = 47;
     /** Key code constant: 'T' key. */
     public static final int KEYCODE_T               = 48;
     /** Key code constant: 'U' key. */
     public static final int KEYCODE_U               = 49;
     /** Key code constant: 'V' key. */
     public static final int KEYCODE_V               = 50;
     /** Key code constant: 'W' key. */
     public static final int KEYCODE_W               = 51;
     /** Key code constant: 'X' key. */
     public static final int KEYCODE_X               = 52;
     /** Key code constant: 'Y' key. */
     public static final int KEYCODE_Y               = 53;
     /** Key code constant: 'Z' key. */
     public static final int KEYCODE_Z               = 54;
     /** Key code constant: ',' key. */
     public static final int KEYCODE_COMMA           = 55;
     /** Key code constant: '.' key. */
     public static final int KEYCODE_PERIOD          = 56;
     /** Key code constant: Left Alt modifier key. */
     public static final int KEYCODE_ALT_LEFT        = 57;
     /** Key code constant: Right Alt modifier key. */
     public static final int KEYCODE_ALT_RIGHT       = 58;
     /** Key code constant: Left Shift modifier key. */
     public static final int KEYCODE_SHIFT_LEFT      = 59;
     /** Key code constant: Right Shift modifier key. */
     public static final int KEYCODE_SHIFT_RIGHT     = 60;
     /** Key code constant: Tab key. */
     public static final int KEYCODE_TAB             = 61;
     /** Key code constant: Space key. */
     public static final int KEYCODE_SPACE           = 62;
     /** Key code constant: Symbol modifier key.
      * Used to enter alternate symbols. */
     public static final int KEYCODE_SYM             = 63;
     /** Key code constant: Explorer special function key.
      * Used to launch a browser application. */
     public static final int KEYCODE_EXPLORER        = 64;
     /** Key code constant: Envelope special function key.
      * Used to launch a mail application. */
     public static final int KEYCODE_ENVELOPE        = 65;
     /** Key code constant: Enter key. */
     public static final int KEYCODE_ENTER           = 66;
     /** Key code constant: Backspace key.
      * Deletes characters before the insertion point, unlike {@link #KEYCODE_FORWARD_DEL}. */
     public static final int KEYCODE_DEL             = 67;
     /** Key code constant: '`' (backtick) key. */
     public static final int KEYCODE_GRAVE           = 68;
     /** Key code constant: '-'. */
     public static final int KEYCODE_MINUS           = 69;
     /** Key code constant: '=' key. */
     public static final int KEYCODE_EQUALS          = 70;
     /** Key code constant: '[' key. */
     public static final int KEYCODE_LEFT_BRACKET    = 71;
     /** Key code constant: ']' key. */
     public static final int KEYCODE_RIGHT_BRACKET   = 72;
 .
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 下面还很多...

根据英语的提示，我们可以很容易地识别出，这些按键的类型，下面举个例子；

 @Override
  2     public boolean onKeyDown(int keyCode, KeyEvent event) {
  3         // TODO Auto-generated method stub
  4
  5         if(keyCode==KeyEvent.KEYCODE_BACK){//back，返回键
  6             Toast.makeText(this,"你按了返回键",LENGTH_LONG).show();
 33         }
 35         return super.onKeyDown(keyCode, event);
 36     }

上面是简单的一个按键时间。一般要处理很多事件的时候，用 switch - case

 @Override
     public boolean onKeyDown(int keyCode, KeyEvent event) {
         // TODO Auto-generated method stub
         if(event.getRepeatCount()==0) {//限制重复次数，防止用户过多点击
             switch(keyCode) {
                 case KeyEvent.KEYCODE_SEARCH:

                     break;
                 case KeyEvent.KEYCODE_CAMERA:

                     break;
                 case KeyEvent.KEYCODE_DPAD_CENTER:

                     break;

                 default:
                     break;
             }
         }
         return super.onKeyDown(keyCode, event);
     }