尝试在空对象引用上调用虚拟方法'java.util.Set android.bluetooth.BluetoothAdapter.getBondedDevices（）'[重复]

Question

此问题已经在这里有了答案：

What is a NullPointerException, and how do I fix it?（12个答案）

[<8天前关闭。

我正在做android应用程序，需要通过蓝牙与特殊Tablo通信。

我在java.lang.NullPointerException上有错误

我已经宣布了我需要的一切。我需要做什么？

Java类

public class SearchTabloActivity extends AppCompatActivity {

    ListView listView;

    BluetoothAdapter mBluetoothAdapter;

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

        listView = (ListView)findViewById(R.id.listView);

        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

        if (mBluetoothAdapter == null) {
            Toast.makeText(getApplicationContext(), "Bluetooth not support!", Toast.LENGTH_SHORT).show();
            startActivity(new Intent(SearchTabloActivity.this, MainActivity.class));
        }

        Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();

        List<String> s = new ArrayList<String>();
        for(BluetoothDevice bt : pairedDevices)
            s.add(bt.getName() + "\n" + bt.getAddress());

        listView.setAdapter(new ArrayAdapter<String>(this, R.layout.activity_search_tablo, s));

    }
}

错误
2020-04-24 09:47:56.208 12121-12121/com.kvaksmanyt.exoy E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.kvaksmanyt.exoy, PID: 12121
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kvaksmanyt.exoy/com.kvaksmanyt.exoy.tablo.SearchTabloActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Set android.bluetooth.BluetoothAdapter.getBondedDevices()' on a null object reference

Answer 1

使用return以任何void方法停止代码