[安卓] 20、基于蓝牙BLE的广播包高频快速搜索
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～
LINKS
[1]. 本项目GITHUB链接地址
[2]. 在Linux下搭建安卓APP的开发烧写环境（makefile版）—— 在Linux上用命令行+VIM开发安卓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]. 等宽字体-Android 设置字体的三种方法（TypeFace）
[10]. Android 设置TextView滑动滚动条和滑动效果
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