通过密钥jsonarray获取价值

Question

JSONArray arr = 
[
    {"key1":"value1"},
    {"key2":"value2"},
    {"key3":"value3"},
    {"key4":"value4"}
]

arr.get("key1") throws error. How can I get the value by key in JSONArray ?

arr.getString("key1") also throws error. Should I loop through the array? Is it the only way to do it?

What is the error?

In Eclipse Debug perspective, these expressions returns as; error(s)_during_the_evaluation

Answer 1

You can parse your jsonResponse like below code :

private void parseJsonData(String jsonResponse){
        try
        {
            JSONArray jsonArray = new JSONArray(jsonResponse);

            for(int i=0;i<jsonArray.length();i++)
            {
                JSONObject jsonObject1 = jsonArray.getJSONObject(i);
                String value1 = jsonObject1.optString("key1");
                String value2 = jsonObject1.optString("key2");
                String value3 = jsonObject1.optString("key3");
                String value4 = jsonObject1.optString("key4");
            }
        }
        catch (JSONException e)
        {
            e.printStackTrace();
        }
    }

Answer 2

Sounds like you want to find a specific key from an array of JSONObjects. Problem is, it's an array, so you have to iterate over each element. One solution, assuming no repeat keys is...

private Object getKey(JSONArray array, String key)
{
    Object value = null;
    for (int i = 0; i < array.length(); i++)
    {
        JSONObject item = array.getJSONObject(i);
        if (item.keySet().contains(key))
        {
            value = item.get(key);
            break;
        }
    }

    return value;
}

Now, let's say you want to find the value of "key1" in the array. You can get the value using the line: String value = (String) getKey(array, "key1") . We cast to a string because we know "key1" refers to a string object.

Answer 3

for (int i = 0; i < arr.length(); ++i) {

    JSONObject jsn = arr.getJSONObject(i);

   String keyVal = jsn.getString("key1");
}

You need to iterate through the array to get each JSONObject. Once you have the object of json you can get values by using keys

Answer 4

You can easy get a JSON array element by key like this:

var value = ArrName['key_1']; //<- ArrName is the name of your array
console.log(value);

Alternatively you can do this too:

var value = ArrName.key_1;

That's it!