在PHP中使用JSON将数据发送到Android

Question

I'm not sure that the JSON codes i have used in my PHP is right to send the data to my Android App. My Android app works fine without any errors. I'm using Async Task to retrieve information from the server using JSON.

This is the code i have used in my Android app to get information from server :

JSONArray arr = new JSONArray(result);
JSONObject jObj = arr.getJSONObject(0);
myoutput = jObj.getString("stringpval");

I havn't displayed the entire code, but i'm sure that all the other codes work fine.

And below is my PHP script used to create a JSON array in PHP:

$a = array(
array('stringpval' => "My Value"));
print $json = json_encode($a);

So i have finished encoding json. I want my TextView in android to display "My Value"! Now when i run my android app and try to get the information from the server, my TextView goes blank. It is Null! What's the problem? Any Solution? Are the above codes correctly used?

Answer 1

The reason is that json_encode($a); is actually returning a JSONObject and not just a JSONArray as you're thinking.

What you're currently printing will look like this:

{
    {
        'stringpval' = "My Value"
    }
}

I'm not sure why you're using a double-array for passing back a single value like that, so for now I would change your PHP file to:

$a = array('stringpval' => "My Value");
print $json = json_encode($a);

Which will return:

{
    'stringpval' = "My Value"
}

Which you could then access in Java by:

JSONObject jObj = new JSONObject(result);
myoutput = jObj.getString("stringpval");

Answer 2

json usually is in two forms, either objects, or arrays, this is very important because you have to know which values are you retrieving from the server(json array or json object?) and hence parse them in the correct manner in the client side. JsonArray are usually like this { "jsonarray_example": [ { "id": "1", "name": "android", "description": "android 4.4.3 kitkat", "updated_at": "0000-00-00 00:00:00" } , { "id": "2", "name": "android", "description": "android 4.1 jellybin", "updated_at": "0000-00-00 00:00:00" } ] } The opening and closing [] marks the array while the {} brackets marks the objects of the array called jsonarray_example but the brackets need not be like that now if your php page outputs something like that then you can retrieve the array else you have to retrieve the objects JsonObject in android so from your problem above you are trying to retrieve jsonObjects while your response is array you should use something like JsonArray result = new JsonArray() ; JsonObject obj = //access the server files result = obj.getJsonArray("stringpval") ; // proceed extracting individual content from the response JsonArray result = new JsonArray() ; JsonObject obj = //access the server files result = obj.getJsonArray("stringpval") ; // proceed extracting individual content from the response

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