[移动开发]Android蓝牙开发（1）：发现设备失败，startDiscovery()返回结果为false

原因：需要配置相关权限，并且位置权限需要进行动态申请

Android官方蓝牙指南

https://developer.android.google.cn/guide/topics/connectivity/bluetooth#SettingUp

配置权限：AndroidManifest.xml

    <uses-permission android:name="android.permission.INTERNET" />
    <!-- 蓝牙权限 -->
    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    <!-- google在android6.0之后，为了更好的保护用户的数据安全，所有需要访问硬件唯一标识符的地方都需要申请位置权限 -->
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

在代码中动态申请位置权限：MainActivity.java

ps:关于动态申请权限的成功/失败处理自行百度

        //判断是否有访问位置的权限，没有权限，直接申请位置权限
        if ((checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
                || (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 200);
        }

广播类：BluetoothBroadcastReceiver.java

public class BluetoothBroadcastReceiver extends BroadcastReceiver {
    private static final String TAG = "BluetoothBroadcastRecei";

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            Log.e(TAG, "设备名字:" + device.getName() + "\n设备地址:" + device.getAddress());
        }
    }
}

检测及开启蓝牙功能：MainActivity.java

@Override
    protected void onCreate(@Nullable @org.jetbrains.annotations.Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //判断是否有访问位置的权限，没有权限，直接申请位置权限
        if ((checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
                || (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 200);
        }

        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        receiver = new BluetoothBroadcastReceiver();
        registerReceiver(receiver, filter);
        
        BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        
        if(bluetoothAdapter!=null){
            // 如果设备存在蓝牙功能
            if(bluetoothAdapter.isEnabled()){
                // 如果蓝牙功能已开启
                if(bluetoothAdapter.isDiscovering()){
                    // 如果正在执行“发现设备”操作
                    bluetoothAdapter.cancelDiscovery();
                }
                else {
                    // 开始“发现设备”！
                    bluetoothAdapter.startDiscovery();
                }
            }
        }
    }
    
    @Override
    protected void onDestroy() {
        super.onDestroy();

        // Don't forget to unregister the ACTION_FOUND receiver.
        unregisterReceiver(receiver);
    }