[安卓] 20、基于蓝牙BLE的广播包高频快速搜索

前言：
1、初始化-onCreate
2、开始扫描-doDiscovery
3、监听
4、权限文件配置
5、最后说明

前言：

之前介绍过很多蓝牙beacon、搜索、连接、通讯的文章。不过最近我发现：之前写的蓝牙广播包搜索的工程，搜索频率太慢，而且不能一直保持搜索状态。因此，这里探讨下高频蓝牙广播包扫描 —— 蓝牙BLE扫描。

注：本文将从对比之前慢的和现在快的两个工程进行展开

1、初始化-onCreate

新的：

// Get the local Bluetooth adapter

// Initializes Bluetooth adapter.

final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);

mBluetoothAdapter = bluetoothManager.getAdapter();

// Ensures Bluetooth is available on the device and it is enabled. If not,

// displays a dialog requesting user permission to enable Bluetooth.

if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {

    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);

    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);

}

老的：

// Register for broadcasts when a device is discovered

IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);

this.registerReceiver(mReceiver, filter);

// Register for broadcasts when discovery has finished

filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);

this.registerReceiver(mReceiver, filter);

// Get the local Bluetooth adapter

mBtAdapter = BluetoothAdapter.getDefaultAdapter();

可见：老的是通过注册广播过滤条件BluetoothDevice.ACTION_FOUND和BluetoothAdapter.ACTION_DISCOVERY_FINISHED，来实现监听蓝牙设备扫描的发现和停止扫描事件。而mReceiver则是回调函数，接下来会介绍；新的暂时看不出啥头绪，仅仅获得bluetoothManager和mBluetoothAdapter，接下来会用到。

2、开始扫描-doDiscovery

新的：

// Start device discover with the BluetoothAdapter

private void doDiscovery() {

    // If we're already discovering, stop it

    if (mBluetoothAdapter.isDiscovering()) {

    	mBluetoothAdapter.stopLeScan(mLeScanCallback);

    }

	// Request discover from BluetoothAdapter

	//use filter not work!!!!!!!!!!

	//UUID[] uuid_arrays = new UUID[1];

	//uuid_arrays[0] = ParcelUuid.fromString(UUID_SERVICE).getUuid();

	//mBluetoothAdapter.startLeScan(uuid_arrays,mLeScanCallback);

	//Log.d("RSSI",uuid_arrays[0].toString() + "  " + UUID.randomUUID().toString());

	mBluetoothAdapter.startLeScan(mLeScanCallback);

}

老的：

// Start device discover with the BluetoothAdapter

private void doDiscovery() {

    // If we're already discovering, stop it

    if (mBtAdapter.isDiscovering()) {

		mBtAdapter.cancelDiscovery();

    }

    // Request discover from BluetoothAdapter

    mBtAdapter.startDiscovery();

}

可见：区别在于一个是BLE操作、一个是普通蓝牙操作。

3、监听

新的：

// Device scan callback.

private BluetoothAdapter.LeScanCallback mLeScanCallback =

	new BluetoothAdapter.LeScanCallback() {

	    @Override

	    public void onLeScan(final BluetoothDevice device, int rssi,

		    byte[] scanRecord) {

				runOnUiThread(new Runnable() {

				    @Override

			public void run() {

				if(device_filter(device)){

				    //mDevicesNameVector.add(device.getName());

				    //mDevicesAddrVector.add(device.getAddress());

				    //mRSSIVector.add((short)rssi);

				    Log.d("RSSI",device.getAddress() + " " + device.getName() + " " + String.valueOf(rssi));

				    ...

				}

			}

		});

	}

};

老的：

// The BroadcastReceiver that listens for discovered devices and

// changes the title when discovery is finished

//【查找蓝牙设备】

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {

	@Override

	public void onReceive(Context context, Intent intent) {

		Log.d("onReceive","OK");

		String action = intent.getAction();

		// When discovery finds a device

		if (BluetoothDevice.ACTION_FOUND.equals(action)) {

			// Get the BluetoothDevice object from the Intent

			BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

			mDevicesNameVector.add(device.getName());

			mDevicesAddrVector.add(device.getAddress());

			short rssi = intent.getExtras().getShort(BluetoothDevice.EXTRA_RSSI);

			mRSSIVector.add(rssi);

			Log.d("RSSI",device.getName()+"  "+String.valueOf(rssi));

			// When discovery is finished, change the Activity title

		} else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {

			setProgressBarIndeterminateVisibility(false);

			if (mDevicesNameVector.size() != 0) {

				Message msg = new Message();//消息

				Bundle bundle = new Bundle();

			    bundle.clear();Log.d("onReceive","1");

			    msg.what = 0x01;//消息类别

			    bundle.putShort("msg",(short) 0);Log.d("onReceive","2");

					msg.setData(bundle);Log.d("onReceive","3");

					myHandler.sendMessage(msg);Log.d("onReceive","4");

			}

		}

	}

};

可见：新的相对比较简单、可以持续不断的扫描获取（同一个设备会被不断的扫描到）；老的则分为两步：第一步是每次扫描到一次新设备都会有一个FOUND事件、最后停止扫描了还有个FINISH事件，这里我在FINISH事件结束时发出一个msg来通知进行其他操作。

4、权限文件配置

新的：

<uses-permission a:name="android.permission.ACCESS_FINE_LOCATION"/>

<uses-permission a:name="android.permission.ACCESS_COARSE_LOCATION"/>

<uses-permission a:name="android.permission.BLUETOOTH"/>

<uses-permission a:name="android.permission.BLUETOOTH_ADMIN"/>

<uses-feature a:name="android.hardware.bluetooth_le" a:required="true"/>

老的：

<uses-permission a:name="android.permission.BLUETOOTH" />

<uses-permission a:name="android.permission.BLUETOOTH_ADMIN" />

<uses-permission a:name="android.permission.ACCESS_COARSE_LOCATION" />

可见： 相差不大，新的比老的多了bluetooth_le说明。

5、最后说明

当你尝试使用BLE SCAN之后，你会感觉有一种飞一般的感觉，几乎同一个设备每一秒都会被扫描到多次。拿这些高频扫描的大量数据，就可以做类似beacon、距离估算、定位等小应用了！效果会比老的scan方法要好很多～

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