Undocumented method of getting battery level in Android. Not recommended, but it can get battery level immediately.

GetBatteryLevel.java

private static final String BATTERY_CAPACITY_SYSFS = "/sys/class/power_supply/battery/capacity";

private static String readSysFsFile(String a_File) throws Exception {
	FileReader a_Reader = new FileReader(a_File);
	int a_Char;
	String a_Content = "";

	while ((a_Char = a_Reader.read()) != -1) {
		// Ignore \n
		if (a_Char != 10) {
			a_Content += Character.toString((char) a_Char);
		}
	}

	return a_Content;
}

public static String getBatteryStatus() {
	try {
		String a_Capacity = readSysFsFile(BATTERY_CAPACITY_SYSFS);

		if (a_Capacity.length() == 0) {
			a_Capacity = "Error";
		}

		return a_Capacity;
	} catch (Exception a_Ex) {
		return "Error";
	}
}