Android - 訪問RadioButton數組的NullPointerException

Question

好的，所以我想我可能會對如何解決這個問題有所瞭解，但我並不確定。我有一段代碼首先聲明一個RadioButton []，然後將其設置爲特定的事物，然後檢查哪個RadioButton被選中的另一個方法。

RadioButton[] rB = null; 

String geUrl(RadioButton[] rBp) { 
    for(int radind = 0; radind < rBp.length; radind++) { 
     Log.d("APP", "rBp value is " + rBp.toString()); 
     Log.d("APP", "In for loop, index = " + radind + ", length = " + rBp.length); 
     if (rBp[radind].isChecked()) { 
      String url = rB[radind].getText().toString(); 
      Log.d("APP", "Detected url, " + url); 
      return url; 
     } 
    } 
    return "err"; 
} 

public void refresh() { 
    if (rB != null) { 
     rG.removeAllViews(); 
    } 
for(int index = 0; index < tempWikiDB.size() ; index++) { 
    rB = new RadioButton[tempWikiDB.size()]; 
    rB[index] = new RadioButton(this); 
    rG.addView(rB[index]); 
    rB[index].setText(tempWikiDB.toArray()[index].toString()); 
} 

}

的geUrl方法以足夠的參數提供。但是，在運行時，如果（rBp [radind] .isChecked（））得到空行指針異常。我認爲這是因爲RadioButton [] rB = null;不是我應該如何聲明變量，但我不知道如何。

這裏的logcat的：

11-23 05:48:27.911: E/AndroidRuntime(1189): FATAL EXCEPTION: main 
11-23 05:48:27.911: E/AndroidRuntime(1189): java.lang.NullPointerException 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at com.spng453.wikicenter.SearchWiki.geUrl(SearchWiki.java:37) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at com.spng453.wikicenter.SearchWiki$1.onClick(SearchWiki.java:74) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.view.View.performClick(View.java:4202) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.view.View$PerformClick.run(View.java:17340) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.os.Handler.handleCallback(Handler.java:725) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.os.Handler.dispatchMessage(Handler.java:92) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.os.Looper.loop(Looper.java:137) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at android.app.ActivityThread.main(ActivityThread.java:5039) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at java.lang.reflect.Method.invoke(Method.java:511) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
11-23 05:48:27.911: E/AndroidRuntime(1189):  at dalvik.system.NativeStart.main(Native Method) 

Answer 1

走這條線了for循環因爲你是初始化rB陣列中的每個循環迭代

rB = new RadioButton[tempWikiDB.size()];