问题描述
在我的Addroid应用程序上,当我尝试开始ble广告时,我正在尝试添加一些额外的数据,而正如我所阅读的,广告数据必须< = 31字节.
On My Addroid app I'm trying to add some extra data when I try to start ble advertising, and as I've read, advertise data must be <= 31 bytes.
这就是我的方法:
var testData = "abcdefghij"
var data = AdvertiseData.Builder().apply {
addServiceData(
ParcelUuid(MY_UUID),
testData.toByteArray(Charsets.UTF_8)
)
}
bleAdvertiser.startAdvertising(
settings.build(),
data.build(),
advertiseCallback
)
通过这种方式,一切正常.现在,如果testData
字段变为
In this way everything works well. Now if testData
fields become
var testData = "abcdefghijk"
由于超出广告数据大小限制,广告开始失败.
advertising starts to fail due to exceeded advertise data size limit.
如果单个字符占用2个字节,为什么我有11个字符的字符串,我超过了30个字节的限制?
If a single char occupies 2 bytes, why if I had a string of 11 characters did I exceed the limit of 30 bytes?
推荐答案
首先会自动添加三个标志字节.
Three flag bytes are automatically added first.
服务数据包包含第一个字节,该字节告诉它有多长时间,其后是一个字节数据包标识符,表示该服务数据包来自此.然后,您将获得服务uuid的有效负载(16个字节),后跟10个字节的UTF-8编码字符串.
A service data packet contains first one byte that tells how long it is, followed by a one byte packet identifier that says that here comes a service data packet. Then you have the payload of the service uuid (16 bytes) followed by your UTF-8-encoded string of 10 bytes.
总和为31个字节.如果添加"k",则将获得32个字节,因此数据变得太长.
That sums up to 31 bytes. If you add a 'k' you get 32 bytes and hence the data becomes too long.
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