Android 启动扫描时，BluetoothLeScanner应用程序崩溃，且不显示任何结果

我看到的错误消息是：

尝试在com.example.drodo.diamondbeacons.bleDeviceActivity.startScanning（bleDeviceActivity.java:91）上的空对象引用上调用虚拟方法“void android.bluetooth.le.BluetoothLeScanner.startScan（java.util.List，android.bluetooth.le.ScanSettings，android.bluetooth.le.ScanCallback）”在com.example.drodo.diamondbeacons.BleDevicesActivity$1.onClick（BleDevicesActivity.java:68）。行中出现错误：mBluetoothLeScanner.startScan（buildScanFilters（）、buildScanSettings（）、mScanCallback）

这是我的密码：

public class BleDevicesActivity extends AppCompatActivity {

private Toolbar bleToolbar;

private static final String TAG = BleDevicesActivity.class.getName();

private static final long SCAN_PERIOD = 5000;

private BluetoothAdapter mBluetoothAdapter;
private BluetoothLeScanner mBluetoothLeScanner;
private ScanCallback mScanCallback;
private TextView deviceName;
private TextView deviceAddress;
private Button scanDevicesBtn;
private Handler mHandler;

public void setBluetoothAdapter(BluetoothAdapter btAdapter) {
    this.mBluetoothAdapter = btAdapter;
    mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_ble_devices);

    mHandler = new Handler();

    bleToolbar = (Toolbar) findViewById(R.id.ble_toolbar);
    setSupportActionBar(bleToolbar);
    getSupportActionBar().setTitle("Ble Devices Nearby");
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    deviceName = (TextView) findViewById(R.id.device_name_text);
    deviceAddress = (TextView) findViewById(R.id.device_address_text);
    scanDevicesBtn = (Button) findViewById(R.id.scan_devices_btn);

    scanDevicesBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startScanning();

            Snackbar.make(v, "Scanning for BLE Devices Nearby", Snackbar.LENGTH_SHORT)
                    .setAction("Action", null).show();
        }
    });
}

public void startScanning() {
    if (mScanCallback == null) {
        Log.d(TAG, "Starting Scanning");

        // Will stop the scanning after a set time.
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                stopScanning();
                Toast.makeText(BleDevicesActivity.this, "Scanning Stopped", Toast.LENGTH_SHORT).show();
            }
        }, SCAN_PERIOD);

        // Kick off a new scan.
        mScanCallback = new SampleScanCallback();
        mBluetoothLeScanner.startScan(buildScanFilters(), buildScanSettings(), mScanCallback);

        String toastText = getString(R.string.scan_start_toast) + " "
                + TimeUnit.SECONDS.convert(SCAN_PERIOD, TimeUnit.MILLISECONDS) + " "
                + getString(R.string.seconds);
        Toast.makeText(BleDevicesActivity.this, toastText, Toast.LENGTH_LONG).show();
    } else {
        Toast.makeText(BleDevicesActivity.this, R.string.already_scanning, Toast.LENGTH_SHORT).show();
    }
}

/**
 * Stop scanning for BLE Advertisements.
 */
public void stopScanning() {
    Log.d(TAG, "Stopping Scanning");

    // Stop the scan, wipe the callback.
    mBluetoothLeScanner.stopScan(mScanCallback);
    mScanCallback = null;

    // Even if no new results, update 'last seen' times.
    //amAdapter.notifyDataSetChanged();
}

/**
 * Return a List of {@link ScanFilter} objects to filter by Service UUID.
 */
private List<ScanFilter> buildScanFilters() {
    List<ScanFilter> scanFilters = new ArrayList<>();

    ScanFilter.Builder builder = new ScanFilter.Builder();
    builder.setServiceUuid(BleConstants.Service_UUID);
    scanFilters.add(builder.build());

    return scanFilters;
}

/**
 * Return a {@link ScanSettings} object set to use low power (to preserve battery life).
 */
private ScanSettings buildScanSettings() {
    ScanSettings.Builder builder = new ScanSettings.Builder();
    builder.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER);
    return builder.build();
}

/**
 * Custom ScanCallback object - adds to adapter on success, displays error on failure.
 */
private class SampleScanCallback extends ScanCallback {

    @Override
    public void onBatchScanResults(List<ScanResult> results) {
        super.onBatchScanResults(results);

        for (ScanResult result : results) {
            String device_name = result.getDevice().getName();
            String device_address = result.getDevice().getAddress();

            deviceName.setText(device_name);
            deviceAddress.setText(device_address);
        }

    }

    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        super.onScanResult(callbackType, result);
        try {
            ScanRecord scanRecord = result.getScanRecord();

            assert scanRecord != null;
            byte[] manufacturerData = scanRecord.getManufacturerSpecificData(0x0590);

            assert manufacturerData != null;

            double lightValue = Double.parseDouble(Arrays.toString(new byte[]{manufacturerData[0]}).replace("[", "").replace("]", ""));
            double tempValue = Double.parseDouble(Arrays.toString(new byte[]{manufacturerData[1]}).replace("[", "").replace("]", ""));
            double batteryValue = Integer.parseInt(Arrays.toString(new byte[]{manufacturerData[2]}).replace("[", "").replace("]", ""));
            int alertPresses = Integer.parseInt(Arrays.toString(new byte[]{manufacturerData[3]}).replace("[", "").replace("]", ""));

            Toast.makeText(BleDevicesActivity.this, "LIGHT: " + lightValue + " %", Toast.LENGTH_SHORT).show();
            Toast.makeText(BleDevicesActivity.this, "TEMPERATURE: " + tempValue + " \u2103", Toast.LENGTH_SHORT).show();
            Toast.makeText(BleDevicesActivity.this, "BATTERY LEVEL: " + batteryValue + " Volts", Toast.LENGTH_SHORT).show();
            Toast.makeText(BleDevicesActivity.this, "ALERT PRESSES: " + alertPresses, Toast.LENGTH_SHORT).show();

        } catch (Exception e) {

            String error_message = e.getMessage();
            Toast.makeText(BleDevicesActivity.this, "Error: " + error_message, Toast.LENGTH_SHORT).show();
        }

    }

    @Override
    public void onScanFailed(int errorCode) {
        super.onScanFailed(errorCode);
        Toast.makeText(BleDevicesActivity.this, "Scan failed with error: " + errorCode, Toast.LENGTH_LONG)
                .show();
    }
}
}

公共类BleDeviceActivity扩展了AppCompatActivity{
专用工具栏；
私有静态最终字符串标记=bleDeviceActivity.class.getName（）；
专用静态最终长扫描周期=5000；
私人蓝牙适配器mBluetoothAdapter；
私人BluetoothLeScanner mBluetoothLeScanner；
专用扫描回拨；
私有文本视图设备名；
私有文本视图设备地址；
私人按钮扫描设备；
私人经理人；
公用适配器（蓝牙适配器btAdapter）{
this.mBluetoothAdapter=btAdapter；
mBluetoothLeScanner=mBluetoothAdapter.getBluetoothLeScanner（）；
}
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity\u ble\u设备）；
mHandler=新处理程序（）；
bleToolbar=（Toolbar）findviewbyd（R.id.ble\u Toolbar）；
设置支持操作栏（工具栏）；
getSupportActionBar（）.setTitle（“附近的可扩展设备”）；
getSupportActionBar（）.setDisplayHomeAsUpEnabled（true）；
deviceName=（TextView）findViewById（R.id.device\u name\u text）；
deviceAddress=（TextView）findViewById（R.id.device\u address\u text）；
scanDevicesBtn=（按钮）findviewbyd（R.id.scan\u devices\u btn）；
scanDevicesBtn.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
开始扫描（）；
Snackbar.make（v，“扫描附近的BLE设备”，Snackbar.LENGTH_SHORT）
.setAction（“Action”，null）.show（）；
}
});
}
公共无效开始扫描（）{
如果（mScanCallback==null）{
Log.d（标签“开始扫描”）；
//将在设定的时间后停止扫描。
mHandler.postDelayed（新的Runnable（）{
@凌驾
公开募捐{
停止扫描（）；
Toast.makeText（bleDeviceActivity.this，“扫描停止”，Toast.LENGTH_SHORT.show（）；
}
}，扫描周期）；
//开始新的扫描。
mScanCallback=新样本Cancallback（）；
开始扫描（buildScanFilters（），buildScanSettings（），mScanCallback）；
String toast text=getString（R.String.scan\u start\u toast）+“
+TimeUnit.SECONDS.convert（扫描周期，TimeUnit.ms）+“
+getString（R.string.seconds）；
Toast.makeText（bleDeviceActivity.this、Toast-Text、Toast.LENGTH_LONG）.show（）；
}否则{
Toast.makeText（bleDeviceActivity.this，R.string.ready_scanning，Toast.LENGTH_SHORT）.show（）；
}
}
/**
*停止扫描不可编辑的广告。
*/
公共无效停止扫描（）{
Log.d（标签“停止扫描”）；
//停止扫描，擦除回调。
mBluetoothLeScanner.stopScan（mScanCallback）；
mScanCallback=null；
//即使没有新结果，也要更新“上次看到”的次数。
//amAdapter.notifyDataSetChanged（）；
}
/**
*返回要按服务UUID筛选的{@link ScanFilter}对象列表。
*/
私有列表buildScanFilters（）{
List scanFilters=新建ArrayList（）；
ScanFilter.Builder=新建ScanFilter.Builder（）；
builder.setServiceUuid（bleContents.Service_UUID）；
添加（builder.build（））；
返回扫描滤波器；
}
/**
*返回{@link ScanSettings}对象集以使用低功耗（以保持电池寿命）。
*/
专用扫描设置buildScanSettings（）{
ScanSettings.Builder=新的ScanSettings.Builder（）；
builder.setScanMode（扫描设置.扫描模式\u低功率）；
返回builder.build（）；
}
/**
*自定义ScanCallback对象-成功时添加到适配器，失败时显示错误。
*/
私有类SampleScanCallback扩展ScanCallback{
@凌驾
public void onBatchScanResults（列出结果）{
super.onBatchScanResults（结果）；
用于（扫描结果：结果）{
字符串device_name=result.getDevice（）.getName（）；
字符串device_address=result.getDevice（）.getAddress（）；
deviceName.setText（设备名称）；
deviceAddress.setText（设备地址）；
}
}
@凌驾
公共void onScanResult（int callbackType、ScanResult）{
super.onScanResult（回调类型、结果）；
试一试{
ScanRecord ScanRecord=result.getScanRecord（）；
断言扫描记录！=null；
字节[]manufacturerData=scanRecord.GetManufacturerSpecificATA（0x0590）；
断言manufacturerData！=null；
double lightValue=double.parseDouble（Arrays.toString（新字节[]{manufacturerData[0]}）。替换（“[”，“”）。替换（“]”，“”）；
double tempValue=double.parseDouble（Arrays.toString（新字节[]{manufacturerData[1]}）。替换（“[”，“”）。替换（“]”，“”）；
double batteryValue=Integer.parseInt（Arrays.toString（新字节[]{manufacturerData[2]}）。替换（“[”，”）。替换（“]，”）；
int alertpress=Integer.parseInt（Arrays.toString（新字节[]{manufacturerData[3]}）。替换（“[”，“”）。替换（“]”，“”）；
Toast.makeText（bleDeviceActivity.this，“LIGHT:+lightValue+“%”，Toast.LENGTH\u SHORT.show（）；
Toast.makeText（bleDeviceActivity.this，“温度：+tempValue+”\u2103”，Toast.LENGTH\u SHORT.show（）；
Toast.makeText（bleDeviceActivity.this，“电池电量：+电池电量值+”伏特），Toast.LENGTH_SHORT.show（）；
烤面包
mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

BluetoothLeScanner scanner = mBluetoothAdapter.getBluetoothLeScanner();
if (scanner != null) {
    scanner.startScan(buildScanFilters(), buildScanSettings(), mScanCallback);
} else {
    // Device Bluetooth is disabled; check and prompt user to enable.
}

BluetoothLeScanner scanner = mBluetoothAdapter.getBluetoothLeScanner();
if (scanner != null) {
    scanner.stopScan(mScanCallback);
} else {
    // Device Bluetooth is disabled; scanning should already be stopped, nothing to do here.
}