[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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