收到关于 json 的错误，我是 Android 世界的新手

Question

I m getting this error when i click a button in Activity im developing a Application in Android studio and getting error about json and im not sure how to handle this error

Error Detail

Attempt to invoke virtual method 'int org.json.JSONArray.length()' on a null object reference at com.example.tourista.DataParser.getAllnearbyPlaces(DataParser.java:62) at com.example.tourista.DataParser.parse(DataParser.java:100)

private List<HashMap<String,String>> getAllnearbyPlaces (JSONArray jsonArray)
{

//Line There i m getting Error

    int counter = jsonArray.length();

    List<HashMap<String,String>> NearbyPlacesList = new ArrayList<>();
    HashMap<String,String> NearbyplaceMap = null;

    if (jsonArray != null) {

        for (int i = 0; i < counter; i++) {
            try {
                NearbyplaceMap = getSingleNearbyPlace((JSONObject) jsonArray.get(i));
                NearbyPlacesList.add(NearbyplaceMap);
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }
    return NearbyPlacesList;
}

public List<HashMap<String,String>>  parse(String JSONdata)
{
    JSONArray jsonArray= null;
    JSONObject jsonObject;


    try
    {
        jsonObject =new JSONObject(JSONdata);
        jsonArray = jsonObject.getJSONArray("results");
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }
    return getAllnearbyPlaces(jsonArray);

}

Answer 1

Your error is for this line : int counter = jsonArray.length();

if you have a null object you can't call any method of that

your jsonArray is null so you can't call jsonArray.length()

you should put int counter = jsonArray.length(); bellow if (jsonArray != null) {

Answer 2

For this specific case

jsonArray = jsonObject.getJSONArray("results") probably throws a JSONException so your array is never initialized and remains null . Look in your logs and you will probably see some red lines of text with the error.

To learn more about Nullpointerexceptions read:

What is a NullPointerException, and how do I fix it?

Answer 3

You need to provide more code. Who is calling the getAllnearbyPlaces (JSONArray jsonArray)?

When this class is called you are passing a null JSONArray