Android BLE BluetoothAdapter.getBluetoothLeScanner（）错误

我正在尝试在我的应用程序中实现蓝牙开发者入门工具包。 但我有以下错误

java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.le.BluetoothLeScanner android.bluetooth.BluetoothAdapter.getBluetoothLeScanner()' on a null object reference

r正在运行以下功能：

public void startScanning(final ScanResultsConsumer scan_results_consumer, long stop_after_ms) {
    if (scanning) {
        Log.d(Constants.TAG, "Already scanning so ignoring startScanning request");
        return;
    }
    Log.d(Constants.TAG, "Scanning...");
    if (scanner == null) {
        scanner = bluetooth_adapter.getBluetoothLeScanner();
        Log.d(Constants.TAG, "Created BluetoothScanner object");
    }
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            if (scanning) {
                Log.d(Constants.TAG, "Stopping scanning");
                scanner.stopScan(scan_callback);
                setScanning(false);
            }
        }
    }, stop_after_ms);

    this.scan_results_consumer = scan_results_consumer;
    List<ScanFilter> filters;
    filters = new ArrayList<ScanFilter>();
    /*ScanFilter filter = new ScanFilter.Builder().setDeviceName("SP5").build();
    filters.add(filter);*/
    ScanSettings settings = new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY).build();
    setScanning(true);
    scanner.startScan(filters, settings, scan_callback);
}

你知道我的蓝牙适配器为什么为空吗？

我解决了这个问题： 在BLEFragment中的onCreateView中：

        ble_scanner = new BLEScanner(this.getContext());

在BLEScanner中：

public BLEScanner(Context context) {
    this.context = context;

    final BluetoothManager bluetoothManager = (BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
    bluetooth_adapter = bluetoothManager.getAdapter();

    // check bluetooth is available and on
    if (bluetooth_adapter == null || !bluetooth_adapter.isEnabled()) {
        Log.d(Constants.TAG, "Bluetooth is NOT switched on");
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        enableBtIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(enableBtIntent);
    }
    Log.d(Constants.TAG, "Bluetooth is switched on");
}

---

蓝牙适配器不为空？

public BLEScanner(Context context) {
    this.context = context;

    final BluetoothManager bluetoothManager = (BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
    bluetooth_adapter = bluetoothManager.getAdapter();

    // check bluetooth is available and on
    if (bluetooth_adapter == null || !bluetooth_adapter.isEnabled()) {
        Log.d(Constants.TAG, "Bluetooth is NOT switched on");
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        enableBtIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(enableBtIntent);
    }
    Log.d(Constants.TAG, "Bluetooth is switched on");
}