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[英]How do I remove all null and empty string values from an object in json java android from retrofit?
[英][UPDATE]How do I access values from the json object?
我是android和JSON的新手。 請幫我找到解決這個問題的方法 - 下面是我的php代碼。
<?php
require "conn.php";
header('Content-Type: application/json');
if(isset($_POST['mailid']))
{
$mailid = $_POST['mailid'];
$today="2017-05-05";//date('Y-m-d');
$mysql_qry = "select employee_id from employee where employee_email='$mailid';";
$result = mysqli_query($conn ,$mysql_qry);
$row = mysqli_fetch_array($result);
$emp_id=$row['employee_id'];
if($emp_id)
{
$sql = "SELECT count(*) from task where employee_id='$emp_id' and task_date='$today';";
$result1 = mysqli_query($conn ,$sql);
$row2=mysqli_fetch_array($result1, MYSQL_ASSOC);
if($result1)
{
$taskcount['count']= $row2['count(*)'];
$taskquery = "select task_name from task where employee_id='$emp_id' and task_date='$today';";
$restask_name=mysqli_query($conn ,$taskquery);
for($i=0;$row1=mysqli_fetch_array($restask_name);$i++)
{
$task_name[]= $row1[0];
}
$taskname['tasks']=$task_name;
$array=array_merge($taskcount,$taskname);
echo json_encode($array);
}
else
{
echo json_encode($taskcount);
}
}
else
{
echo "employee ID doesnt match!!";
}
}
else
{
echo "post variables are not set";
}
?>
我收到來自下面的服務器的回復 -
{
"count": "4",
"tasks": [
"collect paper",
"krishna",
"mys",
"bng" ]
}
我解析json對象的代碼如下 -
if (!result.equals("employee ID doesnt match!!") || !result.equals("post variables are not set")) {
JSONObject json = new JSONObject(result);
MAX_ROWS = Integer.parseInt(json.getString("count"));
System.out.println("rows:"+MAX_ROWS);
JSONArray tasks = json.getJSONArray("tasks");
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
taskname[task_id] = tasks.getString(task_id);//**LINE 153**
System.out.println(taskname[task_id]);
}
}
現在我得到一個空指針異常,這是我的Stacktrace--
05-05 17:41:33.255 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err:java.lang.NullPointerException
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at com.example.anusha.fieldworkemployeetracker.ViewtaskActivity$BackgroundWorker.doInBackground(ViewtaskActivity.java:153)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at com.example.anusha.fieldworkemployeetracker.ViewtaskActivity$BackgroundWorker.doInBackground(ViewtaskActivity.java:107)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
05-05 17:41:33.396 22823-23024/com.example.anusha.fieldworkemployeetracker W/System.err: at java.lang.Thread.run(Thread.java:841)
我怎樣才能做到這一點? 提前致謝。
請嘗試以下代碼:
if (!result.equals("employee ID doesnt match!!") || !result.equals("post variables are not set")) {
JSONObject json = new JSONObject(result);
//JSONObject count = json.getJSONObject("task" + task_id);
JSONArray count = json.getJSONArray("count");
MAX_ROWS = Integer.parseInt(count.getString(0));
System.out.println("rows:" + MAX_ROWS);
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
JSONArray task = json.getJSONArray("task" + String.valueOf(task_id));
taskname[task_id] = task.getString(0);
System.out.println(taskname[task_id]);
}
}
讓Json喜歡;
{ "count":
"4"
,
"tasks0":
"collect paper"
,
"tasks1":
"krishna"
,
"tasks2":
"mys"
,
"tasks3":
"bng"
}
然后解析JSON之上使用以下代碼;
JSONObject json = new JSONObject(jsonResponseString);
String countValue = json.getString("count");
您的代碼中存在多個錯誤:
在這里,您嘗試使用JSONObject
的代碼訪問JSONArray。 例如: count
是JSONArray
。 所以你應該把它解析為JSONArray
。 像這樣:
MAX_ROWS = json.getJSONArray("count").getInt(0);
密鑰名稱是JSONObject中的任務,您應該使用適當的名稱。
JSONArray tasks = json.getJSONArray("tasks" + task_id);
task_name
也是一個JSONArray
,因此您應該相應地處理它。
所以工作代碼應該是這樣的:
MAX_ROWS = json.getJSONArray("count").getInt(0);
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
JSONArray tasks = json.getJSONArray("tasks" + task_id);
taskname[task_id] = task.getString("task_name");
System.out.println(taskname[task_id]);
}
這可能會解決您的問題
JSONObject json = new JSONObject(result);
MAX_ROWS = json.getJSONArray("count").getInt(0);
System.out.println("rows:" + MAX_ROWS);
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
JSONArray task = json.getJSONArray("tasks" + task_id);
taskname[task_id] = task.getString(0);
System.out.println(taskname[task_id]);
}
但是我認為JSON字符串存在更多結構性問題,這使得難以解析為對象。 即你將所有內容存儲為JSONArray(而不是它們的實際類型,例如int或String)。
就個人而言,我會考慮像這樣構造json:
{
"count":4,
"tasks":[
"collect paper",
"do Something else",
"learn about json",
"learn about gson"
]
}
這樣你可以使用以下POJO簡單地(de)使用像Gson這樣的庫來序列化它:
public class TaskHolder {
@SerializedName("count")
@Expose
private Integer count;
@SerializedName("tasks")
@Expose
private List<String> tasks = null;
public Integer getCount() {
return count;
}
public void setCount(Integer count) {
this.count = count;
}
public List<String> getTasks() {
return tasks;
}
public void setTasks(List<String> tasks) {
this.tasks = tasks;
}
}
這樣,操作數據並來回傳遞它會更容易(imho)。 祝好運!
在直接直接了解什么是json以及我們如何在android中使用之前。
對於Json,你知道有兩個括號,第一個是'[]',它顯示為Json數組,另一個是顯示Json對象的'{}',所以如果你想解析json對象的數據那么它的難度如果你完美的話了解json數據的結構,
這是一個解釋你json解析的例子
String jsonData="{"data":["a","b","c"]}";
現在,如果你想訪問當時正好的結構,首先是Object,所以創建JSON對象並將字符串放在Argument中。
JSONObject json=new JSONObject(jsonData);
第二個是數組,所以你需要把內部作為數組,JSONObject和JSONArray對象也提供一些有助於解析數據的defual方法,
JSONArray jsonArray = json.getJsonArray(postion); // postion 1 for'a'String finalData = jsonArray.getString(0);
現在,在嘗試代碼之后,
JSONObject json = new JSONObject(result);
MAX_ROWS = json.getJSONArray("count").getInt(0);
System.out.println("rows:" + MAX_ROWS);
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
JSONObject task = json.getJSONArray("task" + task_id);
taskname[task_id] = task.getString(0);
System.out.println(taskname[task_id]);
}
讓我們將您的json響應視為String結果,並使用以下代碼來解析json
String result = "{\"count\": [\"4\"],\"tasks0\": [\"collect paper\"],\"tasks1\": [\"krishna\"],\"tasks2\": [\"mys\"],\"tasks3\": [\"bng\"]}";
JSONObject json = null;
try {
json = new JSONObject(result);
String countString = json.getJSONArray("count").optString(0, "default_value");
int MAX_ROWS = Integer.parseInt(countString);
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
String taskString = json.getJSONArray("tasks" + task_id).optString(0, "default_value");
Log.d("Task Names", taskString);
}
} catch (JSONException e) {
e.printStackTrace();
}
嘗試這個;
if (!result.equals("employee ID doesnt match!!") || !result.equals("post variables are not set")) {
JSONObject json = new JSONObject(result);
int MAX_ROWS = Integer.parseInt(json.getString("count"));
System.out.println("rows:"+MAX_ROWS);
String taskname[] = new String[MAX_ROWS];
JSONArray tasks = json.getJSONArray("tasks");
for (int task_id = 0; task_id < MAX_ROWS; task_id++) {
taskname[task_id] = tasks.getString(task_id);
System.out.println(tasks.getString(task_id));
}
}
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