记一次通过蓝牙键盘触发事件，在对应的Activity复写onKeyUp每次按键或长按保证只触发一次

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        switch (keyCode) {
            case KeyEvent.KEYCODE_TAB:  // 右上角“左右切换”按钮
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_1: // 用户点击 1
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_2: // 用户点击 2
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_3: // 用户点击 3
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_4: // 用户点击 4
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_5: // 用户点击 5
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_6: // 用户点击 6
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_7: // 用户点击 7
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_8: // 用户点击 8
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_9: // 点 9
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_ADD: // 点“+”
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_SUBTRACT: // 点“-”
                ...
                break;
            case KeyEvent.KEYCODE_NUMPAD_ENTER: // 点“⏎”
                ...
                break;
            case KeyEvent.KEYCODE_9:  // 点“[”
                ...
                break;
            case KeyEvent.KEYCODE_0:   // 点“]”
                ...
                break;
            default:
                break;
        }
        return true;
    }

注意：不同型号手机事件的keyCode可能不同，例如“=”有可能是KEYCODE_EQUALS或者KEYCODE_NUMPAD_EQUALS

接收系统广播对蓝牙开关以及蓝牙键盘的连接状态进行监听，Activity中动态注册广播

 private BluetoothMonitorReceiver bleListenerReceiver = null;


    private void registerBluetoothMonitorReceiver(){
        bleListenerReceiver = new BluetoothMonitorReceiver();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);
        intentFilter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
        intentFilter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
        registerReceiver(bleListenerReceiver, intentFilter);
    }

在onDestroy()中解除注册

   @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterReceiver(bleListenerReceiver);
    }

蓝牙状态监听的广播类

public class BluetoothMonitorReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
        if (action != null) {
            switch (action) {
                case BluetoothAdapter.ACTION_STATE_CHANGED:
                    int blueState = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, 0);
                    switch (blueState) {
                        case BluetoothAdapter.STATE_ON:
                            Toast.makeText(context, "蓝牙已打开", Toast.LENGTH_SHORT).show();
                            break;
                        case BluetoothAdapter.STATE_OFF:
                            Toast.makeText(context, "蓝牙已关闭", Toast.LENGTH_SHORT).show();
                            break;
                    }
                    break;
                case BluetoothDevice.ACTION_ACL_CONNECTED:
                    Toast.makeText(context, "蓝牙设备:" + device.getName() + "已连接", Toast.LENGTH_SHORT).show();
                    break;
                case BluetoothDevice.ACTION_ACL_DISCONNECTED:
                    Toast.makeText(context, "蓝牙设备:" + device.getName() + "已断开", Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }
}

权限（如果需要在程序中开启或关闭蓝牙还需要admin权限）

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

BLE：一般将蓝牙3.0之前的BR/EDR蓝牙称为传统蓝牙，而将蓝牙4.0规范后的BLE（Bluetooh Low Energy）蓝牙称为低功耗蓝牙。蓝牙低能耗技术是短距离、低成本、可互操作性的无线技术，它利用许多智能手段最大限度地降低功耗。

ACL：蓝牙基带技术支持两种连接类型：同步定向连接(SCO)类型和异步无连接(ACL)类型。前者主要用于同步话音传送，后者主要用于分组数据传送。