问题
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 :(
回答1:
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
回答2:
{ // 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();
}
回答3:
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);
回答4:
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.
回答5:
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);
回答6:
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