前言：
之前介紹過很多藍牙beacon、搜索、連接、通訊的文章。不過最近我發現：之前寫的藍牙廣播包搜索的工程，搜索頻率太慢，而且不能一直保持搜索狀態。因此，這里探討下高頻藍牙廣播包掃描 —— 藍牙BLE掃描。
注： 本文將從對比之前慢的和現在快的兩個工程進行展開
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();
可見：老的是通過注冊廣播過濾條件BluetoothDevice.ACTION_FOUND和BluetoothAdapter.ACTION_DISCOVERY_FINISHED，來實現監聽藍牙設備掃描的發現和停止掃描事件。而mReceiver則是回調函數，接下來會介紹；新的暫時看不出啥頭緒，僅僅獲得bluetoothManager和mBluetoothAdapter，接下來會用到。
2、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操作、一個是普通藍牙操作。
3、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、可以持續不斷的掃描獲取（同一個設備會被不斷的掃描到）；老的則分為兩步：第一步是每次掃描到一次新設備都會有一個FOUND事件、最后停止掃描了還有個FINISH事件，這里我在FINISH事件結束時發出一個msg來通知進行其他操作。
4、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。
5、最后說明
當你嘗試使用BLE SCAN之后，你會感覺有一種飛一般的感覺，幾乎同一個設備每一秒都會被掃描到多次。拿這些高頻掃描的大量數據，就可以做類似beacon、距離估算、定位等小應用了！效果會比老的scan方法要好很多～
LINKS
[1]. 本項目GITHUB鏈接地址
[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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