Android增加一个物理按键检测步骤
1:背景介绍
自带按键手机一部，MT6589平台，安卓4.2版本，3.4.5 Linux内核。
2:实现细节
2.1实现kernel层按键事件的上报
首先在KPD_INIT_KEYMAP()中把对应的物理按键定义为KEY_TEST，后面的设置也是根据此表来的。而KEY_TEST在input.h中定义。
文件路径：alps/mediatek/custom/${project}/kernel/dct/dct/cust_kpd.h
/* HW keycode [0 ~ 71] -> Linux keycode*/
#define KPD_INIT_KEYMAP() \
{ \
…
[21] = KEY_TEST, \
…
}Inpu.h中定义KEY_TEST：
路径：alps/kernel/include/linux/input.h
#define KEY_WIMAX 246
#define KEY_RFKILL 247 /* Key that controls all radios */
#define KEY_MICMUTE 248 /* Mute / unmute the microphone */
#define KEY_TEST 249 /* add a test key */
/* Code 255 is reserved for special needs of AT keyboard driver */
Input输入子系统的注册和上报:
输入子系统的注册：
文件路径：/alps/mediatek/platform/mt6589/kernel/drivers/keypad/kpd.c
static int kpd_pdrv_probe(struct platform_device *pdev)
{
…
/* initialize and register input device (/dev/input/eventX) */
kpd_input_dev = input_allocate_device();
…
__set_bit(EV_KEY, kpd_input_dev->evbit);
for (i = 0; i < KPD_NUM_KEYS; i++) {
if (kpd_keymap[i] != 0)
__set_bit(kpd_keymap[i], kpd_input_dev->keybit);
}
…
r = input_register_device(kpd_input_dev);
…
r = request_irq(MT6589_KP_IRQ_ID, kpd_irq_handler, IRQF_TRIGGER_FALLING, KPD_NAME, NULL);
}
其中:
static u16 kpd_keymap[KPD_NUM_KEYS] = KPD_INIT_KEYMAP();//将我们定义的KEY_TEST注册进输入系统.
r = request_irq(MT6589_KP_IRQ_ID, kpd_irq_handler, IRQF_TRIGGER_FALLING, KPD_NAME, NULL); // 这里注册了按键中断和对应的处理函数.接下来分析kpd_irq_handler()函数.
static irqreturn_t kpd_irq_handler(int irq, void *dev_id)
{
/* use _nosync to avoid deadlock */
disable_irq_nosync(MT6589_KP_IRQ_ID);
tasklet_schedule(&kpd_keymap_tasklet);
return IRQ_HANDLED;
}
//由上可知,中断处理函数只简单的调度了一个tasklet.下面我们分析调度的任务:
static DECLARE_TASKLET(kpd_keymap_tasklet, kpd_keymap_handler, 0);
static void kpd_keymap_handler(unsigned long data)
{
…
linux_keycode = kpd_keymap[hw_keycode];
input_report_key(kpd_input_dev, linux_keycode, pressed);
input_sync(kpd_input_dev);
…
}
Linux内核注册上报的流程基本就这样.
2.2编译/验证
./mk r k;
./mk bootimage
运行上面两条命令后,在alps/out/target/product/${project}就会生成bootimage文件，将此文件下载到手机重新启动后，用adb连接，并输入命令;
root@android:/ # getevent /dev/input/event0
点击我们设置的按键，就会上报事件：
0001 00f900000001
0000 0000 00000000
0001 00f900000000
0000 0000 00000000
上面的0xF9即为我们在input.h里面定义的249.
3:增加keypad layout文件键盘映射，linux和android key映射
文件路径：alps/mediatek//config/${project}/mtk-kpd.kl
key 212 CAMERA
key 211 FOCUS
key 249 TEST
4:修改Java识别keycode
路径：/alps/frameworks/base/include/androidfw/keycodelables.h
static const KeycodeLabel KEYCODES[] = {
…
{ "KANA", 218 },
{ "ASSIST", 219 },
{ "TEST", 220 },
// NOTE: If you add a new keycode here you must also add it to several other files.
// Refer to frameworks/base/core/java/android/view/KeyEvent.java for the full list.
{ NULL, 0 }
…
}
路径：/alps/framework /native/include/android/KeyCodes.h
enum {
…
AKEYCODE_TEST = 220,
…
}
5:修改Java键盘事件
路径：alps/frameworks/base/core/java/android/view/KeyEvent.java
public class KeyEvent extends InputEvent implements Parcelable {
…
/** Key code constant: Assist key.
* Launches the global assist activity. Not delivered to applications. */
public static final int KEYCODE_ASSIST = 219;
public static final int KEYCODE_TEST = 220;
private static final int LAST_KEYCODE = KEYCODE_TEST;
…
}
6:修改xml文件描述符
路径：alps/frameworks/base/core/res/res/values/attrs.xml
7:增加验证在android,在此直接打开摄像头。
路径：/alps/frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
在interceptKeyBeforeDispatching()增加:
if(keyCode==KeyEvent.KEYCODE_TEST&&event.getAction()==KeyEvent.ACTION_DOWN)
{
Intent intent = new Intent(MediaStore.INTENT_ACTION_STILL_IMAGE_CAMERA)
.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP
| Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_CLEAR_TASK);
mContext.startActivity(intent);
}