[安卓] 20、基於藍牙BLE的廣播包高頻快速搜索

前言：

以前介紹過不少藍牙beacon、搜索、鏈接、通信的文章。不過最近我發現：以前寫的藍牙廣播包搜索的工程，搜索頻率太慢，並且不能一直保持搜索狀態。所以，這裏探討下高頻藍牙廣播包掃描 —— 藍牙BLE掃描。

注：本文將從對比以前慢的和如今快的兩個工程進行展開

 

一、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();

可見：老的是經過註冊廣播過濾條件BluetoothDevice.ACTION_FOUND和BluetoothAdapter.ACTION_DISCOVERY_FINISHED，來實現監聽藍牙設備掃描的發現和中止掃描事件。而mReceiver則是回調函數，接下來會介紹；新的暫時看不出啥頭緒，僅僅得到bluetoothManager和mBluetoothAdapter，接下來會用到。

 

二、開始掃描-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();
}

可見：區別在於一個是BLE操做、一個是普通藍牙操做。

 

三、監聽

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
//【查找藍牙設備】
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;//消息類別
                bundle.putShort("msg",(short) 0);Log.d("onReceive","2");
                    msg.setData(bundle);Log.d("onReceive","3");
                    myHandler.sendMessage(msg);Log.d("onReceive","4");
            }
        }
    }
};

可見：新的相對比較簡單、能夠持續不斷的掃描獲取（同一個設備會被不斷的掃描到）；老的則分爲兩步：第一步是每次掃描到一次新設備都會有一個FOUND事件、最後中止掃描了還有個FINISH事件，這裏我在FINISH事件結束時發出一個msg來通知進行其餘操做。

 

四、權限文件配置

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" />

可見：相差不大，新的比老的多了bluetooth_le說明。

 

五、最後說明

當你嘗試使用BLE SCAN以後，你會感受有一種飛通常的感受，幾乎同一個設備每一秒都會被掃描到屢次。拿這些高頻掃描的大量數據，就能夠作相似beacon、距離估算、定位等小應用了！效果會比老的scan方法要好不少～

LINKS

[1]. 本項目GITHUB連接地址
[2]. 在Linux下搭建安卓APP的開發燒寫環境（makefile版）—— 在Linux上用命令行+VIM開發安卓APP
[3]. android developer TextView
[4]. android developer Vector
[5]. android developer String
[6]. android developer Formatter
[7]. android developer Matcher
[8]. android developer Pattern
[9]. 等寬字體-Android 設置字體的三種方法（TypeFace）
[10]. Android 設置TextView滑動滾動條和滑動效果

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