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)
This is my main layout
<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
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. By the way, this is the 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 :(
GrIsHu
As Faizan describes in their answer here:
First of all read the Json File from your assests file using below code.
and then you can simply read this string return by this function as
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
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
{ // json object node
"formules": [ // json array formules
{ // json object
"formule": "Linear Motion", // string
"url": "qp1"
}
What you are doing
Context context = null; // context is null
try {
String jsonLocation = AssetJSONFile("formules.json", context);
So change to
try {
String jsonLocation = AssetJSONFile("formules.json", CatList.this);
To parse
I believe you get the string from the assests folder.
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();
}
Method to read JSON file from Assets folder and return as a string object.
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:-
String data = getAssetJsonData(getApplicationContext());
Type type = new TypeToken<Your Data model>() {
}.getType();
<Your Data model> modelObject = new Gson().fromJson(data, type);
With Kotlin have this extension function to read the file return as string.
fun AssetManager.readAssetsFile(fileName : String): String = open(fileName).bufferedReader().use{it.readText()}
Parse the output string using any JSON parser.
Using OKIO
public static String readFileFromAssets(Context context, String fileName) {
try {
InputStream input = context.getAssets().open(fileName);
BufferedSource source = Okio.buffer(Okio.source(input));
return source.readByteString().string(Charset.forName("utf-8"));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
and then...
String data = readFileFromAssets(context, "json/some.json"); //here is my file inside the folder assets/json/some.json
Type reviewType = new TypeToken<List<Object>>() {
}.getType();
Object object = new Gson().fromJson(data, reviewType);
Source code How to fetch Local Json from Assets folder
https://drive.google.com/open?id=1NG1amTVWPNViim_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();
}
}
来源：https://stackoverflow.com/questions/19945411/android-java-how-can-i-parse-a-local-json-file-from-assets-folder-into-a-listvi