Question

首先，我必须说我是Java编程的新手这是我的问题：

我有以下课程：

public class NfcRfConfig {

boolean enabled;
Set<String> tech;

public NfcRfConfig() {
    Log.i(tag, "Contructor");
    enabled = false;
    tech = new HashSet<String>();
}

public void setTech(String techno) {
        tech.add(techno);
}
}

我在我的应用程序中使用它，来自片段：

Map<String, NfcRfConfig> mNfcRfConfig = new HashMap<String, NfcRfConfig>();

public View onCreateView(LayoutInflater inflater,
                         ViewGroup container,
                         Bundle savedInstanceState)
{
    Log.d(tag, "onCreateView()");

    mView = inflater.inflate(R.layout.fragment_rf_config, container, false);

    mContext = getActivity();

    Log.d(tag, "onCreateView() - preparing mNfcRfConfig");
    //NfcRfConfig config = new NfcRfConfig();
    mNfcRfConfig.put(NfcAdapterStExtensions.MODE_READER, new NfcRfConfig());
    mNfcRfConfig.put(NfcAdapterStExtensions.MODE_CE, new NfcRfConfig());
    mNfcRfConfig.put(NfcAdapterStExtensions.MODE_P2P_POLL, new NfcRfConfig());
    mNfcRfConfig.put(NfcAdapterStExtensions.MODE_P2P_LISTEN, new NfcRfConfig());

}

然后我有一堆checkBox，当点击一个时，我想调用我的NfcRfConfig类的方法setTech（）：

    case R.id.pollAReader:
        Log.d(tag, "onClick() - pollAReader");
        NfcRfConfig config1 = mNfcRfConfig.get(NfcAdapterStExtensions.MODE_READER);
        if(box.isChecked() == true)//adds tech to list
        {               
            //Disable other options
            config1.setTech(NfcAdapterStExtensions.TECH_A);
        }
        else // remove tech from list
        {

            config1.removeTech(NfcAdapterStExtensions.TECH_A);
        }

        mNfcRfConfig.put(NfcAdapterStExtensions.MODE_READER, config1);          
        break;

但这是我在logcat中的内容：

D/STNFCINfo2 - RfConfig( 1619): onCreateView()                                                                         
D/STNFCINfo2 - RfConfig( 1619): onCreateView() - preparing mNfcRfConfig                                  
I/NfcRfConfig( 1619): Contructor                                                                         
I/NfcRfConfig( 1619): Contructor                                                                         
I/NfcRfConfig( 1619): Contructor                                                                         
I/NfcRfConfig( 1619): Contructor                                                                                                                             
D/STNFCINfo2 - RfConfig( 1619): onClick() - entry                                                        
D/STNFCINfo2 - RfConfig( 1619): onClick() - pollAReader                                                  
I/NfcRfConfig( 1619): setTech(TECH_A)                                                                    
D/AndroidRuntime( 1619): Shutting down VM                                                                
W/dalvikvm( 1619): threadid=1: thread exiting with uncaught exception (group=0x416bcb90)                 
E/AndroidRuntime( 1619): FATAL EXCEPTION: main                                                           
E/AndroidRuntime( 1619): Process: com.android.stnfcinfo2, PID: 1619                                      
E/AndroidRuntime( 1619): java.lang.NullPointerException                                                  
E/AndroidRuntime( 1619):    at com.st.android.nfc_extensions.NfcRfConfig.setTech(NfcRfConfig.java:31)     
E/AndroidRuntime( 1619):    at com.android.stnfcinfo2.FragmentRfConfig.onClick(FragmentRfConfig.java:140) 
E/AndroidRuntime( 1619):    at android.view.View.performClick(View.java:4424)

这个错误对您来说是否明显？

调用包含set＆lt;＆gt;的类的方法时出现NullPointerException领域

0 个答案: