自定義ArrayAdapter自定義微調器在不同的文件

Question

我正在爲自定義微調器自定義ArrayAdapter。 我使我的自定義ArrayAdapter在一個不同的文件（以保持良好的組織），但我得到一個錯誤。

這是我的活動它有微調：

public class AddEditIncome extends Activity 
{ 
private long rowID; // id of income being edited, if any 

String[] income_names_array,income_description_array,strings; 

//called when the Activity is first started 
@Override 
public void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); // call super's onCreate 
    setContentView(R.layout.add_income); 

    // --- setting spinner for income type --- 
    Spinner s1=(Spinner)findViewById(R.id.spinnerInCategory); 
    ArrayAdapter<String> adapter = new MySpinnerAdapterM(AddEditIncome.this, R.layout.spinner_row, strings); 
    s1.setAdapter(adapter); 
    s1.setOnItemSelectedListener(new OnItemSelectedListener() 
    { 
     @Override 
     public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3){ 
      int index = arg0.getSelectedItemPosition(); 
      inCategory=income_names_array[index]; 
     } 
    @Override 
    public void onNothingSelected(AdapterView<?> arg0) { } 
    }); 
    // --- End of setting spinner--- 

這是在不同的文件我的自定義ArrayAdapter：

public class MySpinnerAdapterM extends ArrayAdapter<String> { 
Context mContext; 
int mResource; 
String[] list; 

String[] strings = {"Salary","Gift","Rent","Freelancer"}; 
    String[] subs = {"Your monthly salary","Its nice to get such gifts..", 
     "Money from renting house", "Thats a difficult job"}; 
int arr_images[] = 
    { R.drawable.salary,R.drawable.gift, R.drawable.rent,R.drawable.freelancer}; 

public MySpinnerAdapterM(Context context, int textViewResourceId, String[] objects) { 
    super(context, textViewResourceId, objects); 
    this.mContext=context; 
    this.mResource=textViewResourceId; 
    this.list=objects; 
} 

@Override 
public View getDropDownView(int position, View convertView,ViewGroup parent) { 
    return getCustomView(position, convertView, parent); 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    return getCustomView(position, convertView, parent); 
} 

public View getCustomView(int position, View convertView, ViewGroup parent) { 

    LayoutInflater inflater = ((Activity)mContext).getLayoutInflater(); 
    View row=inflater.inflate(R.layout.spinner_row, parent, false); 
    TextView label=(TextView)row.findViewById(R.id.company); 
    label.setText(strings[position]); 

    TextView sub=(TextView)row.findViewById(R.id.sub); 
    sub.setText(subs[position]); 

    ImageView icon=(ImageView)row.findViewById(R.id.spinner_image); 
    icon.setImageResource(arr_images[position]); 

    return row; 
    } 
} 

我得到這個錯誤日誌：

02-19 23:24:45.212: E/AndroidRuntime(25529): FATAL EXCEPTION: main 
02-19 23:24:45.212: E/AndroidRuntime(25529): java.lang.RuntimeException: Unable to start activity ComponentInfo{development.nk.esoda/development.nk.esoda.AddEditIncome}: java.lang.NullPointerException 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.os.Handler.dispatchMessage(Handler.java:99) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.os.Looper.loop(Looper.java:123) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread.main(ActivityThread.java:4627) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at java.lang.reflect.Method.invokeNative(Native Method) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at java.lang.reflect.Method.invoke(Method.java:521) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at dalvik.system.NativeStart.main(Native Method) 
02-19 23:24:45.212: E/AndroidRuntime(25529): Caused by: java.lang.NullPointerException 
02-19 23:24:45.212: E/AndroidRuntime(25529): at java.util.Arrays$ArrayList.<init>(Arrays.java:49) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at java.util.Arrays.asList(Arrays.java:171) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:125) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at development.nk.esoda.MySpinnerAdapterM.<init>(MySpinnerAdapterM.java:24) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at development.nk.esoda.AddEditIncome.onCreate(AddEditIncome.java:57) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
02-19 23:24:45.212: E/AndroidRuntime(25529): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
02-19 23:24:45.212: E/AndroidRuntime(25529): ... 11 more 

提前感謝您的努力。

Answer 1

在AddEditIncome聲明數組：

String[] income_names_array,income_description_array,strings; 

但它們是空的，因爲你沒有實際作出陣列。如果您需要使用它們，請妥善製作。

確實，這個問題是因爲你正在調用帶有null數組（AddEditIncome的strings數組變量）的超類構造函數。

我注意到，你是不是在所有的MySpinnerAdapterM使用AddEditIncome.strings，所以你應該通關MySpinnerAdapterM的strings變量，而不是考慮到被初始化：

public MySpinnerAdapterM(Context context, int textViewResourceId, String[] objects) { 
    super(context, textViewResourceId, strings); 
    //rest of code 

這也意味着可以縮短下來MySpinnerAdapterM的構造函數的定義，前提是你總是要使用這些字符串。