Android 长按电源键关机整个流程小学习

           最近研究了一下android关机跟重新启动功能，看了一些长按电源键到弹出关机对话框，到真正关机的一系列处理过程。

首先还是来看看这个长按电源键都干了些什么吧？一般来说，电源键都是接到PMU上的，PMU来判断是长按还短按，当有按键消息产生的时候，系统会有中断，然后去读PMU的状态就可以知道是什么了。笔者以全志平台的AXP209小议一下，先贴上关键代码：

static int axp_battery_event(struct notifier_block *nb, unsigned long event,
        void *data)
{
	struct axp_charger *charger =
	container_of(nb, struct axp_charger, nb);
    uint8_t w[9];
	w[0] = (uint8_t) ((event) & 0xFF);
	w[1] = POWER20_INTSTS2;
	w[2] = (uint8_t) ((event >> 8) & 0xFF);
	w[3] = POWER20_INTSTS3;
	w[4] = (uint8_t) ((event >> 16) & 0xFF);
	w[5] = POWER20_INTSTS4;
	w[6] = (uint8_t) ((event >> 24) & 0xFF);
	w[7] = POWER20_INTSTS5;
	w[8] = (uint8_t) (((uint64_t) event >> 32) & 0xFF);

	if(event & (AXP20_IRQ_BATIN|AXP20_IRQ_BATRE)) {
		axp_capchange(charger);
	}

	if(event & (AXP20_IRQ_ACIN|AXP20_IRQ_USBIN|AXP20_IRQ_ACOV|AXP20_IRQ_USBOV|AXP20_IRQ_CHAOV
				|AXP20_IRQ_CHAST|AXP20_IRQ_TEMOV|AXP20_IRQ_TEMLO)) {
		axp_change(charger);
	}

	if(event & (AXP20_IRQ_ACRE|AXP20_IRQ_USBRE)) {
		axp_change(charger);
	}

	if(event & AXP20_IRQ_PEKLO) {
		axp_presslong(charger);
	}

	if(event & AXP20_IRQ_PEKSH) {
		axp_pressshort(charger);
	}

	DBG_PSY_MSG("event = 0x%x\n",(int) event);
	axp_writes(charger->master,POWER20_INTSTS1,9,w);

	return 0;
}

短按跟长按具体也就是上报的延时区别，如下：

static void axp_presslong(struct axp_charger *charger)
{
	DBG_PSY_MSG("press long\n");
	input_report_key(powerkeydev, KEY_POWER, 1);
	input_sync(powerkeydev);
	ssleep(2);
	DBG_PSY_MSG("press long up\n");
	input_report_key(powerkeydev, KEY_POWER, 0);
	input_sync(powerkeydev);
}

static void axp_pressshort(struct axp_charger *charger)
{
	DBG_PSY_MSG("press short\n");
	input_report_key(powerkeydev, KEY_POWER, 1);
	input_sync(powerkeydev);
	msleep(100);
	input_report_key(powerkeydev, KEY_POWER, 0);
	input_sync(powerkeydev);
}

     在inputmanager里面再解析出是长按还是短按，来做相应处理。如果是长按，就弹出对话框，在弹出对话框之前，有几次传递，还是activitymanger跟Windowsmanagerservice做宏观调控，最终把消息传到苦逼的ShutdownThread，不过ShutdownThread也不难弄。/*****************************************************************************************************/
声明：本博内容均由http://blog.csdn.net/sundesheng125原创，转载请注明出处，谢谢！
/*****************************************************************************************************/

 首先来看一下，在ShutdownThread里面有一个CloseDialogReceiver来关注Intent.ACTION_CLOSE_SYSTEM_DIALOGS，它收到这个消息就会关闭这个对话框。对话框怎么起来的呢？请看下面的源码：

        if (confirm) {
            final CloseDialogReceiver closer = new CloseDialogReceiver(context);
            final AlertDialog dialog = new AlertDialog.Builder(context)
                    .setTitle(com.android.internal.R.string.power_off)
                    .setMessage(resourceId)
                    .setPositiveButton(com.android.internal.R.string.yes, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            beginShutdownSequence(context);
                        }
                    })
                    .setNegativeButton(com.android.internal.R.string.no, null)
                    .create();
            closer.dialog = dialog;
            dialog.setOnDismissListener(closer);
            dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
            dialog.show();
        } else {
            beginShutdownSequence(context);
        }

    其实就是一个AlertDialog，也没什么新鲜的，只是在setPositiveButton的时候注册了clicklistener来监听你是否按下了，按下了就直接执行beginShutdownSequence。在beginShutdownSequence还会弹出一个进度的对话框，代码如下：

        ProgressDialog pd = new ProgressDialog(context);
        pd.setTitle(context.getText(com.android.internal.R.string.power_off));
        pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));
        pd.setIndeterminate(true);
        pd.setCancelable(false);
        pd.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);

        pd.show();

      在里面还会调用两个非常重要的Power.shutdown()跟Power.reboot(reason)，看你是重启还是关机了。

    /**
     * Low-level function turn the device off immediately, without trying
     * to be clean.  Most people should use
     * {@link android.internal.app.ShutdownThread} for a clean shutdown.
     *
     * @deprecated
     * @hide
     */
    @Deprecated
    public static native void shutdown();

    /**
     * Reboot the device.
     * @param reason code to pass to the kernel (e.g. "recovery"), or null.
     *
     * @throws IOException if reboot fails for some reason (eg, lack of
     *         permission)
     */
    public static void reboot(String reason) throws IOException
    {
        rebootNative(reason);
    }

    private static native void rebootNative(String reason) throws IOException ;

      再往下跟，

static void android_os_Power_shutdown(JNIEnv *env, jobject clazz)
{
    android_reboot(ANDROID_RB_POWEROFF, 0, 0);
}

extern int go_recovery(void);

static void android_os_Power_reboot(JNIEnv *env, jobject clazz, jstring reason)
{
    if (reason == NULL) {
        android_reboot(ANDROID_RB_RESTART, 0, 0);
    } else {
        const char *chars = env->GetStringUTFChars(reason, NULL);
        //android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars);
        go_recovery();
        android_reboot(ANDROID_RB_RESTART, 0, 0);
        env->ReleaseStringUTFChars(reason, chars);  // In case it fails.
    }
    jniThrowIOException(env, errno);
}

 所以，整个流程都是好的，学习理了一下流程，大部分都是源码，把它搞清楚也是有好处的。