如何直接將數據添加到arrayAdapter？

Question

我試圖從Bluetooth - Android Developers

Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); 
// If there are paired devices 
if (pairedDevices.size() > 0) { 
    // Loop through paired devices 
    for (BluetoothDevice device : pairedDevices) { 
     // Add the name and address to an array adapter to show in a ListView 
     mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); 
    } 
} 

使用此代碼，但我不能將數據添加到myArrayAdapter，因爲它放置在private void onCreate()相加法拋出錯誤，有沒有這樣的適配器。

我需要直接將數據添加到一個ArrayAdapter，因爲它應該在我的活動列表視圖刷新時，發現了一些新的設備。

另外我可以使用myArrayAdapter.notifyDataSetChanged()，但就像我說我的ArrayAdapter置於onCreate，所以它無法訪問它。

所以我的問題是如何在onCreate之外放置arrayAdapter而沒有任何錯誤？

我的Java類代碼，如果neccesary：

public class DeviceList extends AppCompatActivity { 

    private final static int REQUEST_ENABLE_BT = 1; 

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

     BluetoothAdapter BTAdapter = BluetoothAdapter.getDefaultAdapter(); 
     if (BTAdapter != null) { 
      if (!BTAdapter.isEnabled()) { 
       Intent enableBT = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
       startActivityForResult(enableBT, REQUEST_ENABLE_BT); 
      } 
      if (BTAdapter.isDiscovering()) { 
       BTAdapter.cancelDiscovery(); 
      } 
      BTAdapter.startDiscovery(); 
     } 

     ArrayAdapter<String> myArrayAdapter; 
     ListView listView = (ListView) findViewById(R.id.inputELM); 
     myArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myEntries); 
     listView.setAdapter(myArrayAdapter); 

     // Register the BroadcastReceiver 
     IntentFilter ifilter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 
     this.registerReceiver(mReceiver, ifilter); 
    } 

    ArrayList<String> myEntries = new ArrayList<>(); 
    // Create a BroadcastReceiver for ACTION_FOUND 
    private final BroadcastReceiver mReceiver = new BroadcastReceiver() { 
     public void onReceive(Context context, Intent intent) { 
      String action = intent.getAction(); 
      // When discovery finds a device 
      if (BluetoothDevice.ACTION_FOUND.equals(action)) { 
       // Get the BluetoothDevice object from the Intent 
       BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
       // Add the name and address to an array adapter to show in a ListView 
       String devs = device.getName() + "\n" + device.getAddress(); 
       myEntries.add(devs); 

      } 
     } 
    }; 
} 

Answer 1

只需將超出onCreate

public class DeviceList extends AppCompatActivity { 

    private final static int REQUEST_ENABLE_BT = 1; 

    // Declare here 
    private ArrayAdapter<String> myArrayAdapter; 

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

     BluetoothAdapter BTAdapter = BluetoothAdapter.getDefaultAdapter(); 
     if (BTAdapter != null) { 
      if (!BTAdapter.isEnabled()) { 
       Intent enableBT = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
       startActivityForResult(enableBT, REQUEST_ENABLE_BT); 
      } 
      if (BTAdapter.isDiscovering()) { 
       BTAdapter.cancelDiscovery(); 
      } 
      BTAdapter.startDiscovery(); 
     } 

     ListView listView = (ListView) findViewById(R.id.inputELM); 
     myArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myEntries); 
     listView.setAdapter(myArrayAdapter); 

     // Register the BroadcastReceiver 
     IntentFilter ifilter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 
     this.registerReceiver(mReceiver, ifilter); 
    } 

    ArrayList<String> myEntries = new ArrayList<>(); 
    // Create a BroadcastReceiver for ACTION_FOUND 
    private final BroadcastReceiver mReceiver = new BroadcastReceiver() { 
     public void onReceive(Context context, Intent intent) { 
      String action = intent.getAction(); 
      // When discovery finds a device 
      if (BluetoothDevice.ACTION_FOUND.equals(action)) { 
       // Get the BluetoothDevice object from the Intent 
       BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
       // Add the name and address to an array adapter to show in a ListView 
       String devs = device.getName() + "\n" + device.getAddress(); 
       myEntries.add(devs); 
      } 
     } 
    }; 
} 

Answer 2

只要寫

ArrayAdapter myArrayAdapter;

與你的靜態變量聲明，所以你可以從所有的方法訪問它。然後你可以從任何地方訪問它。