本文介绍Xamarin.Form的蓝牙使用方法，开始之前说说题外话，就Xamarin.Form来说，在国内是没多少人在弄的，但对于我自己来说，是吃了这碗饭，也希望在这行做的人越来越多，越来越好，本人2016年开始入使用Xamarin.Form开发App，那时候刚微软刚收购Xamarin，也正式开源免费给开发者使用，但那时候的本说实话是有多不完善的，直到现在微软依然有很多不完善的功能，所以在国内学这个，一般是由公司高层推这个技术，直接至底向上的非常少。微软的东西在国内环境来说，多不太好，很多大的互联网公司都比较少用，但是我要强调的是，Xamarin.Form本身其实并不太适合做界面变化太多，变化太大的东西，如果你的项目需要优秀的界面，炫酷的特效，那原生是比较好的选择，而这个特性是互联网公司的特性，所以互联网公司不太适合使用Xamarin.Form。Xamarin适合界面少，但是业务比较复杂的项目，如IOT项目。也比较适合传统企业而不是互联网公司。所以在前面一篇文章中，我介绍了MQTT协议，现在介绍底功耗蓝牙协议。
这里使用ble.net库，直接使用nuget查找相应的包就可以了，ble.net库是一个混合平台的低功耗蓝牙库，可用于开发Android、iOS、UWP平台的BLE客户端。支持的平台和版本如下
| Platform | Version |
| Xamarin.iOS | iOS 8.3+ |
| Xamarin.Android | API 18+ |
| Windows 10(UWP) | 1709+ |
在引用包的时候注意：在Xamarin.Form层引用ble.net包，在xamarin.Android层引用ble.net 和ble.net-android包，在Xamarin.Form层引用ble.net和ble.net-ios包。
Android 平台
添加权限，在Android 6.0或更高版本中需要获取危险的位置权限，所以在AndroidManifesst.xml文件中添加
1 <uses-permission android:name="android.permission.BLUETOOTH" /> 2 <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /> 3 <uses-permission android:name="android.permission.BLUETOOTH_PRIVILEGED" /> 4 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> 5 <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 6 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
初始化BluetoothLowEnergyAdapter(只有Android平台需要，iOS和UWP平台不需要)。如果你想让IBluetoothLowEnergyAdapter.DisableAdapter() 和 IBluetoothLowEnergyAdapter.EnableAdapter()起作用，你需要在你的Main Activity中添加：
protected override void OnCreate( Bundle bundle )
{
// ...
BluetoothLowEnergyAdapter.Init( this );
// ...
}
如果你要IBluetoothLowEnergyAdapter.CurrentState.Subscribe()方法起作用，你还需要在Activity中添加：
protected sealed override void OnActivityResult( Int32 requestCode, Result resultCode, Intent data )
{
BluetoothLowEnergyAdapter.OnActivityResult( requestCode, resultCode, data );
}
iOS 平台
必须添加使用蓝牙的提示，并且苹果公司上架App会审核，需正确填写Info.plist文件
1 <key>UIBackgroundModes</key> 2 <array> 3 <string>bluetooth-central</string> 4 </array> 5 <key>NSBluetoothPeripheralUsageDescription</key> 6 <string>[MyAppNameHere] would like to use bluetooth.</string>
所有平台都需要初始化一个
IBluetoothLowEnergyAdapter ble = BluetoothLowEnergyAdapter.ObtainDefaultAdapter()
同时传到Xamarin.Form层。
App内开启蓝牙：使用如下方法检查和启用手机蓝牙适配器
if(ble.AdapterCanBeEnabled && ble.CurrentState.IsDisabledOrDisabling()) {
await ble.EnableAdapter();
}
开始扫描附近的蓝牙设备，可以扫描到各种设备，注意：超时时间不宜设置过长，通过测试，蓝牙设备不能一直扫描，需停一会在扫描一会这样使用。扫描能扫描出附近的蓝牙设备和特性。
var cts = new CancellationTokenSource(TimeSpan.FromSeconds( 30 ));
await ble.ScanForBroadcasts(
// providing ScanSettings is optional
new ScanSettings()
{
// Setting the scan mode is currently only applicable to Android and has no effect on other platforms.
// If not provided, defaults to ScanMode.Balanced
Mode = ScanMode.LowPower,
// Optional scan filter to ensure that the observer will only receive peripherals
// that pass the filter. If you want to scan for everything around, omit the filter.
Filter = new ScanFilter()
{
AdvertisedDeviceName = "foobar",
AdvertisedManufacturerCompanyId = 76,
// peripherals must advertise at-least-one of any GUIDs in this list
AdvertisedServiceIsInList = new List<Guid>(){ someGuid },
},
// ignore repeated advertisements from the same device during this scan
IgnoreRepeatBroadcasts = false
},
// Your IObserver<IBlePeripheral> or Action<IBlePeripheral> will be triggered for each discovered
// peripheral based on the provided scan settings and filter (if any).
( IBlePeripheral peripheral ) =>
{
// read the advertising data
var adv = peripheral.Advertisement;
Debug.WriteLine( adv.DeviceName );
Debug.WriteLine( adv.Services.Select( x => x.ToString() ).Join( "," ) );
Debug.WriteLine( adv.ManufacturerSpecificData.FirstOrDefault().CompanyName() );
Debug.WriteLine( adv.ServiceData );
// if we found what we needed, stop the scan manually
cts.Cancel();
// perhaps connect to the device (see next example)...
},
// Provide a CancellationToken to stop the scan, or use the overload that takes a TimeSpan.
// If you omit this argument, the scan will timeout after BluetoothLowEnergyUtils.DefaultScanTimeout
cts.Token
);
// scanning has stopped when code reached this point since the scan was awaited
如果你要连接蓝牙设备，采用如下方法：
var connection = await ble.ConnectToDevice(
// The IBlePeripheral to connect to
peripheral,
// TimeSpan or CancellationToken to stop the
// connection attempt.
// If you omit this argument, it will use
// BluetoothLowEnergyUtils.DefaultConnectionTimeout
TimeSpan.FromSeconds( 15 ),
// Optional IProgress<ConnectionProgress>
progress => Debug.WriteLine(progress)
);
if(connection.IsSuccessful())
{
var gattServer = connection.GattServer;
// ... do things with gattServer here... (see later examples...)
}
else
{
// Do something to inform user or otherwise handle unsuccessful connection.
Debug.WriteLine( "Error connecting to device. result={0:g}", connection.ConnectionResult );
// e.g., "Error connecting to device. result=ConnectionAttemptCancelled"
}
断开蓝牙方法：
await gattServer.Disconnect();
下列方法用来连接指定的蓝牙设备：
var connection = await ble.FindAndConnectToDevice(
new ScanFilter()
.SetAdvertisedDeviceName( "foo" )
.SetAdvertisedManufacturerCompanyId( 0xffff )
.AddAdvertisedService( guid ),
TimeSpan.FromSeconds( 30 ) );
if(connection.IsSuccessful())
{
// ...
}
调用蓝牙的读特性
try
{
var value = await gattServer.ReadCharacteristicValue( someServiceGuid, someCharacteristicGuid );
}
catch(GattException ex)
{
Debug.WriteLine( ex.ToString() );
}
监听通知特性
IDisposable notifyHandler;
try
{
// Will also stop listening when gattServer
// is disconnected, so if that is acceptable,
// you don‘t need to store this disposable.
notifyHandler = gattServer.NotifyCharacteristicValue(
someServiceGuid,
someCharacteristicGuid,
// IObserver<Tuple<Guid, Byte[]>> or IObserver<Byte[]> or
// Action<Tuple<Guid, Byte[]>> or Action<Byte[]>
bytes => {/* do something with notification bytes */} );
}
catch(GattException ex)
{
Debug.WriteLine( ex.ToString() );
}
// ... later, once done listening for notifications ...
notifyHandler.Dispose();
调用写特性，注意：在写的时候不能一直不停的调用这个方法，不然会发送不了，需要停顿500毫秒左右在发送第二个包。这点非常重要。
try
{
// The resulting value of the characteristic is returned. In nearly all cases this
// will be the same value that was provided to the write call (e.g. `byte[]{ 1, 2, 3 }`)
var value = await gattServer.WriteCharacteristicValue(
someServiceGuid,
someCharacteristicGuid,
new byte[]{ 1, 2, 3 } );
}
catch(GattException ex)
{
Debug.WriteLine( ex.ToString() );
}
蓝牙有很多应用，需要自己多尝试，对于蓝牙的升级DFU功能，需要的可以找我。
原文地址：https://www.cnblogs.com/zuimengaitianya/p/12153093.html