如果在Android棒棒糖中关闭蓝牙，Android ble应用程序将崩溃

你好，我正在尝试扫描蓝牙设备上的Android棒棒糖。它工作正常，但如果关闭bluetooth，然后运行应用程序，它将崩溃，然后弹出窗口以启用蓝牙。理想情况下，如果关闭，它应该弹出窗口以启用蓝牙

这是应启用蓝牙的方法：

   private void enableBluetooth() { 
   if(bluetoothAdapter == null) {
     //bluetoothState.setText("Bluetooth NOT supported"); } 
   else if(!bluetoothAdapter.isEnabled()) {
     //bluetoothAdapter.enable(); 
     Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
     activity.startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); 
     } 
   }

开始扫描的代码

public void handleScanStart(View view) {
        foundDevices.clear();
        btArrayAdapter.clear();
        ble.startBleScan();
        scanButton.setEnabled(false);
       stopScanButton.setEnabled(true);
}

启用开始扫描

  public void startBleScan() {
        if(getScanning()) {
           return;
       }

          enableBluetooth();
         scanning = true;


         ScanFilter.Builder filterBuilder = new ScanFilter.Builder();                     //TODO currently default, scans all devices
        ScanSettings.Builder settingsBuilder = new               ScanSettings.Builder();
        settingsBuilder.setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY);
             List<ScanFilter> filters = new ArrayList<ScanFilter>();
                  filters.add(filterBuilder.build());
                   bluetoothLeScanner.startScan(filters, settingsBuilder.build(), scanCallback);

           Log.d(TAG, "Bluetooth is currently scanning...");
                      }

---

您可以通过对话框告诉用户蓝牙未启用，然后在用户点击OK（或点击Cancel）时为其启用蓝牙，代码如下：

final BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

if (!bluetoothAdapter.isEnabled()) {
 final AlertDialog.Builder builder = new AlertDialog.Builder(this);
 builder.setTitle("Bluetooth not enabled");
 builder.setMessage("Press OK to enable bluetooth");
 builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
  @Override
  public void onClick(DialogInterface dialog, int which) {
   Log.d(TAG, "Enabling bluetooth");
   bluetoothAdapter.enable();
  }
 });
 builder.setNegativeButton(android.R.string.cancel, null);
 builder.show();
}

---

正确的方法是，在开始扫描之前，我们必须检查BluetoothLeScanner对象是否为空，就像检查BluetoothAdapter一样

样品

if(bluetoothLeScanner != null){
             bluetoothLeScanner.startScan(filters,settingsBuilder.build(),scanCallback);

    }

---

你的BluetoothLeScanner似乎没有被初始化。请添加您的方法代码。private void enablebooth（）{if（bluetoothAdapter==null）{//bluetoothState.setText（“蓝牙不支持”）；}else if（！bluetoothAdapter.isEnabled（））{//bluetoothAdapter.enable（）；Intent enablebttent=new Intent（bluetoothAdapter.ACTION_请求_启用）；activity.startActivityForResult（enableBtIntent，REQUEST_ENABLE_BT）；}}这是一种使Bluetooth IT能够在android kitkat上正常工作的方法。在棒棒糖中，应用程序首先崩溃，然后显示弹出窗口以启用蓝牙。请用显示

MyActivity的代码摘录编辑上述问题。handleScanStart

if(bluetoothLeScanner != null){
             bluetoothLeScanner.startScan(filters,settingsBuilder.build(),scanCallback);

    }