java - 从Json数组中获取指定值

Question

你怎么样

我需要访问数据库并从表中读取数据，然后获取它的值，因此我创建一个 php 文件以 JSON 格式打印数据库以访问数据:

<?php
try{
    $db=new PDO('mysql:host=localhost;dbname='database','table','password');
    $row=$db->prepare('select * from users' );
    $row->execute();
    $json_data=array();
    foreach($row as $rec)
    {
        $json_array['userId']=$rec['userId'];
        $json_array['user']=$rec['user'];
        $json_array['pass']=$rec['pass'];
        $json_array['name']=$rec['name'];
        $json_array['family']=$rec['family'];
        $json_array['gender']=$rec['gender'];
        $json_array['birthday']=$rec['birthday'];

        array_push($json_data,$json_array);
    }
    echo json_encode($json_data);
} catch(PDOExcetion $e)
{
    print "Error: " . $e->getMessage()."<br/>";
    die();
}
?>

这是输出:

[
    {"userId":"1","user":"saly","pass":"666","name":"SalyR","family":"manson","gender":"male","birthday":"1988\/11\/10"},
    {"userId":"1","user":"foo","pass":"2657","name":"foo","family":"rocki","gender":"male","birthday":"13989\/2\/07"},
    {"userId":"1","user":"mil","pass":"63495","name":"milo","family":"toufa","gender":"male","birthday":"13987\/04\/21"},
    {"userId":"1","user":"soos","pass":"03468","name":"soro","family":"radi","gender":"female","birthday":"13990\/08\/09"}
]

我想访问指定的值，例如“userId”、“name”和“birthday”。

我使用三种方法来获取值:

1) getJSONFromDatabase 方法获取数据库 URL 并返回 JSON 字符串。

public String getJSONFromDatabase(String getDatabaseURL) {
        HttpClient client = new DefaultHttpClient();
        HttpPost method = new HttpPost(getDatabaseURL);
        String result = "";

        try {
            HttpResponse response = client.execute(method);
            int code = response.getStatusLine().getStatusCode();
            InputStream stream = response.getEntity().getContent();
            result = inputstreamToString(stream);
            Log.i("LOG", "Code :" + code);
        } catch (IOException e) {
            Log.e("Database", "Error Connect to Database!");
            e.printStackTrace();
        }
        return result;
    }

2) inputstreamToString 方法获取输入流并读取所有行。

private String inputstreamToString(InputStream getStream) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(getStream));
        StringBuilder builder = new StringBuilder();
        String line;

        try {
            while ((line = reader.readLine()) != null) {
                builder.append(line);
            }
            return builder.toString();
        } catch (IOException e) {
            Log.e("Reader", "Error reading stream!");
            e.printStackTrace();
        }
        return "";
    }

3) jsonToString 方法获取带有我们想要获取的字符串值的 JSON 字符串。

public String jsonToString(String getJSONString, String value) {
        String userId = "";
        try {
            JSONObject object = new JSONObject(getJSONString);
            userId = object.getString(value);
            return userId;

        } catch (JSONException e) {
            Log.e("JSON", "Error converting!");
            e.printStackTrace();
        }
        return "";
    }

所以我调用这样的方法:

String databaseURL = "http://192.168.56.1/saly/getDatabaseTable.php";
String jsonFormat = getJSONFromDatabase(databaseURL);
String userId = jsonToString(jsonFormat, "userId");
String name= jsonToString(jsonFormat, "name");
String birthday= jsonToString(jsonFormat, "birthday");

最后我在日志中收到以下错误:

JSON: Error converting!  

JSON: Error converting!  

JSON: Error converting!

当我删除 [ ] 并像这个 JSON 字符串一样写入一行时，它可以正常工作，只需一行!:

{
    "userId":"1",
    "user":"saly",
    "pass":"666",
    "name":"SalyR",
    "family":"manson",
    "gender":"male",
    "birthday":"1988\/11\/10"
}

但这对我不起作用，因为当我以 JSON 格式打印数据库的所有表时，整个数据都会打印。

我写了太多，对此感到抱歉，我尝试解释每件事。你能帮我解决我错的地方吗？

谢谢。

Answer 1

您必须将其解析为 jsonArray。以下 fragment 将对您有所帮助。

JSONArray jsonarray = new JSONArray(str);//str= your json string.


for(int i=0; i<jsonarray.length(); i++){
    JSONObject obj = jsonarray.getJSONObject(i);

    String name = obj.getString("name");
    String url = obj.getString("url");

    System.out.println(name);
    System.out.println(url);
}   

Here这是这个问题的答案。