數組適配器NotifyDataSetChanged（）NullPointerException Android

我正在向列表中添加一個映射，然後刷新陣列適配器。這在早期工作完美，但現在我使用了來自兩種不同方法的addItem（）方法，它引發了一個NullPointer。我希望我的代碼將清理我所說的話：數組適配器NotifyDataSetChanged（）NullPointerException Android

SimpleAdapter adapter; 
List<HashMap<String, String>> painItems = new ArrayList<HashMap<String, String>>(); 
ListView listthings; 
int[] to; 
String[] from; 
String painLevelString, timeOfPainString, textTreatmentString, 
     painLocation, row1, row2, name; 

OnCreate(){ 
if(getIntent().getStringExtra("newPainLevel")!= null){ 
     createNewEditedEntry(); 

     } 
    adapter = new SimpleAdapter(this, painItems, R.layout.mylistlayout, 
      from, to); 
    listthings.setAdapter(adapter); 
} 

private void createNewEditedEntry() { 
    String newPainLevel = this.getIntent().getStringExtra("newPainLevel"); 
    String newPainTime =this.getIntent().getStringExtra("newPainTime"); 
    String newTreatment =this.getIntent().getStringExtra("newTreatment"); 
    painLevelString = newPainLevel; 
    timeOfPainString = newPainTime; 
    textTreatmentString = newTreatment; 
    row1 = "sample1"; 
    row2 = "sample2"; 

    addItem(); 
    //painItems.remove(getIntent().getStringExtra("position")); 
    //adapter.notifyDataSetChanged(); 

} 

@Override 
// on the activityresult,get the string extra, then add the item to the list 
protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
    if (resultCode == 1) { 
     row1 = data.getStringExtra("com.painLogger.row1"); 
     row2 = data.getStringExtra("com.painLogger.row2"); 


     painLevelString = data.getStringExtra("com.painLogger.painLevel"); 
     painLocation = data.getStringExtra("painLocation"); 
     timeOfPainString = data.getStringExtra("com.painLogger.painTime"); 
     textTreatmentString = data 
       .getStringExtra("com.painLogger.treatment"); 
     addItem(); 
    } 
} 

// to add the item, put it in the map, and add the map into the list 
private void addItem() { 
    HashMap<String, String> map = new HashMap<String, String>(); 
    map.put("row_1", row1); 
    map.put("row_2", row2); 
    map.put("row_3", painLevelString); 
    map.put("row_4", painLocation); 
    map.put("row_5", timeOfPainString); 
    map.put("row_6",textTreatmentString); 
    painItems.add(map); 
     adapter.notifyDataSetChanged(); //Null Pointer **HERE** 
    }

只是要清楚，createNewEditedEntry（）和onActivityResult（）在同一時間從來不被稱爲永不發生衝突。他們是兩個完全不同的事件。它只使用OnActivityResult，但現在當我使用CreateNewEditedEntry（）時，它已停止工作。我也檢查並確保我從我的意圖中獲取的任何字符串都不爲空。

來源

2011-08-01 Kgrover

需要初始化adapter你onCreate調用createNewEditedEntry前：

OnCreate(){ 
    adapter = new SimpleAdapter(this, painItems, R.layout.mylistlayout, from, to); 
     if(getIntent().getStringExtra("newPainLevel")!= null){ 
     createNewEditedEntry();  
     } 
// ... 
}

否則，adapter將是無效的addItem從那裏被稱爲（的createNewEditedEntry最後一行）。

來源

2011-08-01 05:52:31 MByD

非常感謝您的回覆！我不能接受答案（它不會讓我再等3分鐘），但我認爲它解決了它（我遇到了另一個（無關的）錯誤）。 – Kgrover

@Kgrover - 您歡迎。 – MByD

您還應該注意，如果您在進行子活動時您的活動被Android銷燬，您的addItem調用可能會失敗。閱讀我對this question的回答，瞭解資源不足時可能發生的情況。

來源

2013-04-28 17:10:33 Phil

數組適配器NotifyDataSetChanged（）NullPointerException Android

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