[英]How can I parse a local JSON file from assets folder into a ListView?
I'm currently developing a physics app that is supposed to show a list of formulas and even solve some of them (the only problem is the ListView
)我目前正在开发一个物理应用程序,它应该显示一个公式列表,甚至解决其中的一些(唯一的问题是
ListView
)
This is my main layout这是我的主要布局
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:measureWithLargestChild="false"
android:orientation="vertical"
tools:context=".CatList" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/titlebar" >
<TextView
android:id="@+id/Title1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="@string/app_name"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#ff1c00"
android:textIsSelectable="false" />
</RelativeLayout>
<ListView
android:id="@+id/listFormulas"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
And this is my main activity这是我的主要活动
package com.wildsushii.quickphysics;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.res.AssetManager;
import android.view.Menu;
import android.widget.ListView;
public class CatList extends Activity {
public static String AssetJSONFile (String filename, Context context) throws IOException {
AssetManager manager = context.getAssets();
InputStream file = manager.open(filename);
byte[] formArray = new byte[file.available()];
file.read(formArray);
file.close();
return new String(formArray);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cat_list);
ListView categoriesL = (ListView)findViewById(R.id.listFormulas);
ArrayList<HashMap<String, String>> formList = new ArrayList<HashMap<String, String>>();
Context context = null;
try {
String jsonLocation = AssetJSONFile("formules.json", context);
JSONObject formArray = (new JSONObject()).getJSONObject("formules");
String formule = formArray.getString("formule");
String url = formArray.getString("url");
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
//My problem is here!!
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.cat_list, menu);
return true;
}
}
I actually know I can make this without using JSON but I need more practice parsing JSON.我实际上知道我可以在不使用 JSON 的情况下做到这一点,但我需要更多练习解析 JSON。 By the way, this is the JSON
顺便说一句,这是 JSON
{
"formules": [
{
"formule": "Linear Motion",
"url": "qp1"
},
{
"formule": "Constant Acceleration Motion",
"url": "qp2"
},
{
"formule": "Projectile Motion",
"url": "qp3"
},
{
"formule": "Force",
"url": "qp4"
},
{
"formule": "Work, Power, Energy",
"url": "qp5"
},
{
"formule": "Rotary Motion",
"url": "qp6"
},
{
"formule": "Harmonic Motion",
"url": "qp7"
},
{
"formule": "Gravity",
"url": "qp8"
},
{
"formule": "Lateral and Longitudinal Waves",
"url": "qp9"
},
{
"formule": "Sound Waves",
"url": "qp10"
},
{
"formule": "Electrostatics",
"url": "qp11"
},
{
"formule": "Direct Current",
"url": "qp12"
},
{
"formule": "Magnetic Field",
"url": "qp13"
},
{
"formule": "Alternating Current",
"url": "qp14"
},
{
"formule": "Thermodynamics",
"url": "qp15"
},
{
"formule": "Hydrogen Atom",
"url": "qp16"
},
{
"formule": "Optics",
"url": "qp17"
},
{
"formule": "Modern Physics",
"url": "qp18"
},
{
"formule": "Hydrostatics",
"url": "qp19"
},
{
"formule": "Astronomy",
"url": "qp20"
}
]
}
I have tried a lot of things and even delete the entire project to make a new one:(我已经尝试了很多东西,甚至删除了整个项目以创建一个新项目:(
As Faizan describes in their answer here :正如 Faizan 在他们的回答中所描述的:
First of all read the Json File from your assests file using below code.首先,使用以下代码从您的资产文件中读取 Json 文件。
and then you can simply read this string return by this function as然后你可以简单地读取这个函数返回的字符串作为
public String loadJSONFromAsset() {
String json = null;
try {
InputStream is = getActivity().getAssets().open("yourfilename.json");
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
json = new String(buffer, "UTF-8");
} catch (IOException ex) {
ex.printStackTrace();
return null;
}
return json;
}
and use this method like that并像那样使用这种方法
try {
JSONObject obj = new JSONObject(loadJSONFromAsset());
JSONArray m_jArry = obj.getJSONArray("formules");
ArrayList<HashMap<String, String>> formList = new ArrayList<HashMap<String, String>>();
HashMap<String, String> m_li;
for (int i = 0; i < m_jArry.length(); i++) {
JSONObject jo_inside = m_jArry.getJSONObject(i);
Log.d("Details-->", jo_inside.getString("formule"));
String formula_value = jo_inside.getString("formule");
String url_value = jo_inside.getString("url");
//Add your values in your `ArrayList` as below:
m_li = new HashMap<String, String>();
m_li.put("formule", formula_value);
m_li.put("url", url_value);
formList.add(m_li);
}
} catch (JSONException e) {
e.printStackTrace();
}
For further details regarding JSON Read HERE有关 JSON 的更多详细信息,请阅读此处
{ // json object node
"formules": [ // json array formules
{ // json object
"formule": "Linear Motion", // string
"url": "qp1"
}
What you are doing你在做什么
Context context = null; // context is null
try {
String jsonLocation = AssetJSONFile("formules.json", context);
So change to所以改为
try {
String jsonLocation = AssetJSONFile("formules.json", CatList.this);
To parse解析
I believe you get the string from the assests folder.我相信你从assests文件夹中得到了字符串。
try
{
String jsonLocation = AssetJSONFile("formules.json", context);
JSONObject jsonobject = new JSONObject(jsonLocation);
JSONArray jarray = (JSONArray) jsonobject.getJSONArray("formules");
for(int i=0;i<jarray.length();i++)
{
JSONObject jb =(JSONObject) jarray.get(i);
String formula = jb.getString("formule");
String url = jb.getString("url");
}
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
With Kotlin have this extension function to read the file return as string. Kotlin 有这个扩展函数来读取作为字符串返回的文件。
fun AssetManager.readAssetsFile(fileName : String): String = open(fileName).bufferedReader().use{it.readText()}
Parse the output string using any JSON parser.使用任何 JSON 解析器解析输出字符串。
Method to read JSON file from Assets folder and return as a string object.从 Assets 文件夹读取 JSON 文件并作为字符串对象返回的方法。
public static String getAssetJsonData(Context context) {
String json = null;
try {
InputStream is = context.getAssets().open("myJson.json");
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
json = new String(buffer, "UTF-8");
} catch (IOException ex) {
ex.printStackTrace();
return null;
}
Log.e("data", json);
return json;
}
Now for parsing data in your activity:-现在解析您活动中的数据:-
String data = getAssetJsonData(getApplicationContext());
Type type = new TypeToken<Your Data model>() {
}.getType();
<Your Data model> modelObject = new Gson().fromJson(data, type);
Just summarising @libing's answer with a sample that worked for me.只是用一个对我有用的样本总结@libing 的回答。
val gson = Gson()
val todoItem: TodoItem = gson.fromJson(this.assets.readAssetsFile("versus.json"), TodoItem::class.java)
private fun AssetManager.readAssetsFile(fileName : String): String = open(fileName).bufferedReader().use{it.readText()}
Without this extension function the same can be achieved by using BufferedReader
and InputStreamReader
this way:如果没有这个扩展函数,同样可以通过使用
BufferedReader
和InputStreamReader
来实现:
val i: InputStream = this.assets.open("versus.json")
val br = BufferedReader(InputStreamReader(i))
val todoItem: TodoItem = gson.fromJson(br, TodoItem::class.java)
implementation("com.squareup.okio:okio:3.0.0-alpha.4")
With Java:使用 Java:
public static String readJsonFromAssets(Context context, String filePath) {
try {
InputStream input = context.getAssets().open(filePath);
BufferedSource source = Okio.buffer(Okio.source(input));
return source.readByteString().string(Charset.forName("utf-8"));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
With Kotlin:使用科特林:
fun readJsonFromAssets(context: Context, filePath: String): String? {
try {
val source = context.assets.open(filePath).source().buffer()
return source.readByteString().string(Charset.forName("utf-8"))
} catch (e: IOException) {
e.printStackTrace()
}
return null
}
and then...接着...
String data = readJsonFromAssets(context, "json/some.json"); //here is my file inside the folder assets/json/some.json
Type reviewType = new TypeToken<List<Object>>() {}.getType();
if (data != null) {
Object object = new Gson().fromJson(data, reviewType);
}
You have to write a function to read the Json File from your assests folder.
public String loadJSONFile() {
String json = null;
try {
InputStream inputStream = getAssets().open("yourfilename.json");
int size = inputStream.available();
byte[] byteArray = new byte[size];
inputStream.read(byteArray);
inputStream.close();
json = new String(byteArray, "UTF-8");
} catch (IOException e) {
e.printStackTrace();
return null;
}
return json;
}
Source code How to fetch Local Json from Assets folder源代码 如何从 Assets 文件夹中获取本地 Json
https://drive.google.com/open?id=1NG1amTVWPNViim_caBr8eeB4zczTDK2p https://drive.google.com/open?id=1NG1amTVWPPNViim_caBr8eeB4zczTDK2p
{
"responseCode": "200",
"responseMessage": "Recode Fetch Successfully!",
"responseTime": "10:22",
"employeesList": [
{
"empId": "1",
"empName": "Keshav",
"empFatherName": "Mr Ramesh Chand Gera",
"empSalary": "9654267338",
"empDesignation": "Sr. Java Developer",
"leaveBalance": "3",
"pfBalance": "60,000",
"pfAccountNo.": "12345678"
},
{
"empId": "2",
"empName": "Ram",
"empFatherName": "Mr Dasrath ji",
"empSalary": "9999999999",
"empDesignation": "Sr. Java Developer",
"leaveBalance": "3",
"pfBalance": "60,000",
"pfAccountNo.": "12345678"
},
{
"empId": "3",
"empName": "Manisha",
"empFatherName": "Mr Ramesh Chand Gera",
"empSalary": "8826420999",
"empDesignation": "BusinessMan",
"leaveBalance": "3",
"pfBalance": "60,000",
"pfAccountNo.": "12345678"
},
{
"empId": "4",
"empName": "Happy",
"empFatherName": "Mr Ramesh Chand Gera",
"empSalary": "9582401701",
"empDesignation": "Two Wheeler",
"leaveBalance": "3",
"pfBalance": "60,000",
"pfAccountNo.": "12345678"
},
{
"empId": "5",
"empName": "Ritu",
"empFatherName": "Mr Keshav Gera",
"empSalary": "8888888888",
"empDesignation": "Sararat Vibhag",
"leaveBalance": "3",
"pfBalance": "60,000",
"pfAccountNo.": "12345678"
}
]
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_employee);
emp_recycler_view = (RecyclerView) findViewById(R.id.emp_recycler_view);
emp_recycler_view.setLayoutManager(new LinearLayoutManager(EmployeeActivity.this,
LinearLayoutManager.VERTICAL, false));
emp_recycler_view.setItemAnimator(new DefaultItemAnimator());
employeeAdapter = new EmployeeAdapter(EmployeeActivity.this , employeeModelArrayList);
emp_recycler_view.setAdapter(employeeAdapter);
getJsonFileFromLocally();
}
public String loadJSONFromAsset() {
String json = null;
try {
InputStream is = EmployeeActivity.this.getAssets().open("employees.json"); //TODO Json File name from assets folder
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
json = new String(buffer, "UTF-8");
} catch (IOException ex) {
ex.printStackTrace();
return null;
}
return json;
}
private void getJsonFileFromLocally() {
try {
JSONObject jsonObject = new JSONObject(loadJSONFromAsset());
String responseCode = jsonObject.getString("responseCode");
String responseMessage = jsonObject.getString("responseMessage");
String responseTime = jsonObject.getString("responseTime");
Log.e("keshav", "responseCode -->" + responseCode);
Log.e("keshav", "responseMessage -->" + responseMessage);
Log.e("keshav", "responseTime -->" + responseTime);
if(responseCode.equals("200")){
}else{
Toast.makeText(this, "No Receord Found ", Toast.LENGTH_SHORT).show();
}
JSONArray jsonArray = jsonObject.getJSONArray("employeesList"); //TODO pass array object name
Log.e("keshav", "m_jArry -->" + jsonArray.length());
for (int i = 0; i < jsonArray.length(); i++)
{
EmployeeModel employeeModel = new EmployeeModel();
JSONObject jsonObjectEmployee = jsonArray.getJSONObject(i);
String empId = jsonObjectEmployee.getString("empId");
String empName = jsonObjectEmployee.getString("empName");
String empDesignation = jsonObjectEmployee.getString("empDesignation");
String empSalary = jsonObjectEmployee.getString("empSalary");
String empFatherName = jsonObjectEmployee.getString("empFatherName");
employeeModel.setEmpId(""+empId);
employeeModel.setEmpName(""+empName);
employeeModel.setEmpDesignation(""+empDesignation);
employeeModel.setEmpSalary(""+empSalary);
employeeModel.setEmpFatherNamer(""+empFatherName);
employeeModelArrayList.add(employeeModel);
} // for
if(employeeModelArrayList!=null) {
employeeAdapter.dataChanged(employeeModelArrayList);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
If you are using Kotlin in android then you can create Extension function .如果您在 android 中使用Kotlin ,那么您可以创建扩展功能。
Extension Functions are defined outside of any class - yet they reference the class name and can use this
.扩展函数是在任何类之外定义的——但它们引用类名并可以使用
this
。 In our case we use applicationContext
.在我们的例子中,我们使用
applicationContext
。
So in Utility class you can define all extension functions.所以在 Utility 类中你可以定义所有的扩展函数。
Utility.kt实用程序.kt
fun Context.loadJSONFromAssets(fileName: String): String {
return applicationContext.assets.open(fileName).bufferedReader().use { reader ->
reader.readText()
}
}
MainActivity.kt主活动.kt
You can define private function for load JSON data from assert like this:您可以像这样定义用于从断言加载 JSON 数据的私有函数:
lateinit var facilityModelList: ArrayList<FacilityModel>
private fun bindJSONDataInFacilityList() {
facilityModelList = ArrayList<FacilityModel>()
val facilityJsonArray = JSONArray(loadJSONFromAsserts("NDoH_facility_list.json")) // Extension Function call here
for (i in 0 until facilityJsonArray.length()){
val facilityModel = FacilityModel()
val facilityJSONObject = facilityJsonArray.getJSONObject(i)
facilityModel.Facility = facilityJSONObject.getString("Facility")
facilityModel.District = facilityJSONObject.getString("District")
facilityModel.Province = facilityJSONObject.getString("Province")
facilityModel.Subdistrict = facilityJSONObject.getString("Facility")
facilityModel.code = facilityJSONObject.getInt("code")
facilityModel.gps_latitude = facilityJSONObject.getDouble("gps_latitude")
facilityModel.gps_longitude = facilityJSONObject.getDouble("gps_longitude")
facilityModelList.add(facilityModel)
}
}
You have to pass facilityModelList
in your ListView
你必须通过
facilityModelList
在您ListView
FacilityModel.kt设施模型.kt
class FacilityModel: Serializable {
var District: String = ""
var Facility: String = ""
var Province: String = ""
var Subdistrict: String = ""
var code: Int = 0
var gps_latitude: Double= 0.0
var gps_longitude: Double= 0.0
}
In my case JSON response start with JSONArray在我的情况下,JSON 响应以 JSONArray 开头
[
{
"code": 875933,
"Province": "Eastern Cape",
"District": "Amathole DM",
"Subdistrict": "Amahlathi LM",
"Facility": "Amabele Clinic",
"gps_latitude": -32.6634,
"gps_longitude": 27.5239
},
{
"code": 455242,
"Province": "Eastern Cape",
"District": "Amathole DM",
"Subdistrict": "Amahlathi LM",
"Facility": "Burnshill Clinic",
"gps_latitude": -32.7686,
"gps_longitude": 27.055
}
]
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