Question

可能重复：
NullPointerException for ArrayAdapter in android

这是我的代码

String[] city_array = response_city.toString().split(",");  
Log.d("city array", city_array[0]);  
ArrayAdapter<String> cityArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line);  
Log.d("city array adapter","count1 = " + cityArrayAdapter.getCount());  
cityArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);  
int length = city_array.length;  
for (int i = 0; i < length; i++)
    cityArrayAdapter.add(city_array[i]);  
Log.d("city array adapter","count2 = " + cityArrayAdapter.getCount());  
city_spinner.setAdapter(cityArrayAdapter);

第一步中的response_city是来自网络服务器的回复，其中包含“pune，mumbai，bangalore”

Answer 1

我没有看到city_spinner初始化的位置。记录city_spinner，如果为null，则表明您已发现问题。空指针异常通常意味着某些东西没有被初始化，并且它似乎很可能是罪魁祸首。

Answer 2

像这样改变

String[] city_array = response_city.toString().split(",");  
Log.d("city array", city_array[0]);  
ArrayLlist<String> items = new ArrayList<String>();

int length = city_array.length;  
for (int i = 0; i < length; i++)
items.add(city_array[i]);

ArrayAdapter<String> cityArrayAdapter = new ArrayAdapter<String>(this,    
android.R.layout.simple_dropdown_item_1line, items);  
Log.d("city array adapter","count1 = " + cityArrayAdapter.getCount());  
cityArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);  

Log.d("city array adapter","count2 = " + cityArrayAdapter.getCount());  
city_spinner.setAdapter(cityArrayAdapter);

Answer 3

city_spinner检查是否正确分配了XML视图....

android中setAdapter步骤期间ArrayAdapter的NullPointerException

3 个答案: