嗨,我对 android studio 还很陌生
我有这个 JSON 树
[
{
"id": 1,
"name": "jhon",
"salary": 1500
},
{
"id": 2,
"name": "sal",
"salary": 1700
},
{
"id": 3,
"name": "bob",
"salary": 2500
},
{
"id": 4,
"name": "ned",
"salary": 1800
},
{
"id": 5,
"name": "mike",
"salary": 1300
}
]
我的项目分为三个部分。
首先,用户可以在 EditText
小部件中输入一个 Int 来显示与 id 对应的名称的 toast。
第三种是最小最大搜索,用户输入两个整数来搜索它们之间的所有工资。
但第二部分是我遇到问题的地方,我有一个员工姓名的 spinner
,用户应该选择一个姓名,然后单击 btnSearchName
按钮来显示该员工的信息Search_by_name.xml
中 TextView
中的相应用户(ID 名称和薪水),但是当我单击搜索按钮
时,我会被带到XML 文件,但 employeeInfo
TextView 为空,并且没有错误消息或崩溃,只是一个空 Activity ,我无法弄清楚。
这是MainActivity.java
package com.hfad.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText editId = findViewById(R.id.editId);
final EditText editMin = findViewById(R.id.editMin);
final EditText editMax = findViewById(R.id.editMax);
final Spinner spName = findViewById(R.id.spinnerName);
final String url = "https://api.myjson.com/bins/dxnri";
final ArrayList<String> employeeName = new ArrayList<>();
JsonArrayRequest jsonSpinner = new JsonArrayRequest(Request.Method.GET, url,
null,new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
try {
for (int i = 0; i < response.length(); i++) {
JSONObject st = response.getJSONObject(i);
String name = st.getString("name");
employeeName.add(name);
}
spName.setAdapter(new ArrayAdapter<String>(MainActivity.this,
android.R.layout.simple_spinner_dropdown_item, employeeName));
} catch (JSONException e) { e.printStackTrace(); }
} }, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.i("error", error.toString());
}
});
MySingleton.getMInstance(MainActivity.this).addToRequestQueue(jsonSpinner);
Button btnSearchId = findViewById(R.id.btnSearchId);
btnSearchId.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
JsonArrayRequest jsonId = new JsonArrayRequest(Request.Method.GET, url,
null,new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
try {
boolean found = false;
for (int i = 0; i < response.length(); i++) {
String name;
JSONObject st = response.getJSONObject(i);
int id = st.getInt("id");
if(id == Integer.parseInt(editId.getText().toString())) {
name = st.getString("name");
Toast.makeText(getApplicationContext(),
"The employee's name is " + name,
Toast.LENGTH_LONG).show();
found = true;
break;
}
}
if(!found)
Toast.makeText(getApplicationContext(),"Invalid Id",
Toast.LENGTH_LONG).show();
} catch (JSONException e) { e.printStackTrace(); }
} }, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.i("error", error.toString());
}
});
MySingleton.getMInstance(MainActivity.this).addToRequestQueue(jsonId);
}
});
Button btnSearchName = findViewById(R.id.btnSearchName);
btnSearchName.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, SearchByName.class);
intent.putExtra("EmployeeName", spName.getSelectedItem().toString());
startActivity(intent);
}
});
Button btnSearchSalary = findViewById(R.id.btnSearchSalary);
btnSearchSalary.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, SearchBysalary.class);
intent.putExtra("salaryMin", editMin.getText().toString());
intent.putExtra("salaryMax", editMax.getText().toString());
startActivity(intent);
}
});
}
}
MainActivity.XML
<?xml version="1.0" encoding="UTF-8"?>
<androidx.constraintlayout.widget.ConstraintLayout tools:context=".MainActivity" android:layout_height="match_parent" android:layout_width="match_parent" xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android">
<EditText android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toStartOf="@+id/btnSearchId"
app:layout_constraintBottom_toTopOf="@+id/spinnerName"
android:inputType="number"
android:hint="id"
android:ems="10"
android:id="@+id/editId"/>
<EditText
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="@+id/editMax"
android:inputType="textPersonName"
android:hint="salary min"
android:ems="10" android:id="@+id/editMin"
app:layout_constraintEnd_toEndOf="parent"/>
<EditText
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="@+id/btnSearchSalary"
android:inputType="textPersonName"
android:hint="salary max"
android:ems="10" android:id="@+id/editMax"
app:layout_constraintEnd_toEndOf="parent"/>
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toTopOf="@+id/btnSearchName"
android:id="@+id/btnSearchId"
app:layout_constraintEnd_toEndOf="parent"
android:text="SEARCH BY ID"/>
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toTopOf="@+id/btnSearchSalary"
android:id="@+id/btnSearchName"
app:layout_constraintEnd_toEndOf="parent"
android:text="SEARCH BY NAME"/>
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
android:id="@+id/btnSearchSalary"
app:layout_constraintEnd_toEndOf="parent"
android:text="SEARCH BY SALARY"
app:layout_constraintBottom_toBottomOf="parent"/>
<Spinner
android:layout_height="24dp"
android:layout_width="208dp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toStartOf="@+id/btnSearchName"
app:layout_constraintBottom_toTopOf="@+id/btnSearchSalary"
android:id="@+id/spinnerName"
app:layout_constraintVertical_bias="0.493"
app:layout_constraintHorizontal_bias="0.688"/>
</androidx.constraintlayout.widget.ConstraintLayout>
SearchByName.java
package com.hfad.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
public class SearchByName extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search_by_name);
final TextView employeeInfo = findViewById(R.id.employeeInfo);
final String employeeName = getIntent().getStringExtra("name");
final Spinner spName = findViewById(R.id.spinnerName);
String url = "https://api.myjson.com/bins/dxnri";
JsonArrayRequest jsonName = new JsonArrayRequest(Request.Method.GET, url,
null,new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
try {
for (int i = 0; i < response.length(); i++) {
JSONObject st = response.getJSONObject(i);
int id = st.getInt("id");
String name = st.getString("name");
int salary = st.getInt("salary");
if(name.equals(employeeName)) {
employeeInfo.setText("Id: " + id + "\n\nName: " + name + "\n\nSalary: " + salary);
break;
// "Id: " + id + "\n\nName: " + name + "\n\nSalary: " + salary
}
}
} catch (JSONException e) { e.printStackTrace(); }
} }, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.i("error", error.toString());
}
});
MySingleton.getMInstance(SearchByName.this).addToRequestQueue(jsonName);
}
}
和searchbyname.XML
,其中应显示spinnerName
中所选名称的姓名、id、薪水
<?xml version="1.0" encoding="UTF-8"?>
<androidx.constraintlayout.widget.ConstraintLayout tools:context=".SearchByName" android:layout_height="match_parent" android:layout_width="match_parent" xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android">
<TextView
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
android:textSize="32dp"
android:text="TextView"
android:id="@+id/employeeInfo"/>
</androidx.constraintlayout.widget.ConstraintLayout>
最佳答案
您的问题是您试图启动已启动的同一 Activity 。那是行不通的。如果 Activity 正在运行,则不会再次调用 onCreated
。
您应该执行以下操作之一:
- 在您的
MainActivity
方法onNewIntent
中使用 ovveride 并在此处执行所有 JSON 逻辑 - 忘记 Intent 并使用
AsyncTask
(已弃用)或其他异步模式来完成工作
关于java - 从 json 文件填充 TextView 不起作用,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/59874495/