我是Android新手。我遇到的一个问题是ArrayAdapter实现。阅读这么多教程，需要确保我理解正确。
这是我试图解决的问题：
require 'rails_helper'
RSpec.describe "Users", type: :request do
let(:user) { create(:user) }
describe "GET /users/:id" do
it "takes a username as the id param" do
get user_path(user.user_name)
expect(response).to be_successful
end
end
end
我的观点有textview和listview
package hfad.com.adapters;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
public class MainActivity extends Activity {
//thorntech.com parsing jsonandroid using colley library
TextView results;
// URL of object to be parsed
String JsonURL = "https://raw.githubusercontent.com/ianbar20/JSON-Volley-Tutorial/master/Example-JSON-Files/Example-Array.JSON";
// This string will hold the results
String data = "";
// Defining the Volley request queue that handles the URL request concurrently
ListView myList;
RequestQueue requestQueue;
//Adding adapter and assign it -set- to a listview
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Creates the Volley request queue
requestQueue = Volley.newRequestQueue(this);
// Casts results into the TextView found within the main layout XML with id jsonData
results = (TextView) findViewById(R.id.textView);
myList = (ListView) findViewById(R.id.listv);
final ArrayAdapter myAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1);
ListView myList = (ListView) findViewById(R.id.listv);
myList.setAdapter(myAdapter);
// Creating the JsonArrayRequest class called arrayreq, passing the required parameters
//JsonURL is the URL to be fetched from
JsonArrayRequest arrayreq = new JsonArrayRequest(JsonURL,
// The second parameter Listener overrides the method onResponse() and passes
//JSONArray as a parameter
new Response.Listener<JSONArray>() {
// Takes the response from the JSON request
@Override
public void onResponse(JSONArray response) {
/* ================================================================== */
/* //////////////////////// Example using TextView and it works////////////////////// */
//url https://reqres.in/api/users?page=2
try {
// Retrieves first JSON object in outer array
JSONObject colorObj = response.getJSONObject(0);
// Retrieves "colorArray" from the JSON object
JSONArray colorArry = colorObj.getJSONArray("colorArray");
// Iterates through the JSON Array getting objects and adding them
//to the list view until there are no more objects in colorArray
for (int i = 0; i < colorArry.length(); i++) {
//gets each JSON object within the JSON array
JSONObject jsonObject = colorArry.getJSONObject(i);
// Retrieves the string labeled "colorName" and "hexValue",
// and converts them into javascript objects
String color = jsonObject.getString("colorName");
String hex = jsonObject.getString("hexValue");
// Adds strings from the current object to the data string
//spacing is included at the end to separate the results from
//one another
data += "\n"+ "Color Number " + (i + 1) + "\n"+"Color Name: " + color +
"\n"+ "nHex Value : " + hex + "nnn"+ "\n";
}
// Adds the data string to the TextView "results"
results.setText(data);
}
/* ============================================================ */
/* ////////////////////////// Example 2 working /////////////////////////////// */
//url https://raw.githubusercontent.com/ianbar20/JSON-Volley-Tutorial/master/Example-JSON-Files/Example-Array.JSON
/*
try {
// Retrieves first JSON object in outer array
JSONObject colorObj = response.getJSONObject(0);
// Retrieves "colorArray" from the JSON object
JSONArray colorArry = colorObj.getJSONArray("colorArray");
// Iterates through the JSON Array getting objects and adding them
//to the list view until there are no more objects in colorArray
for (int i = 0; i < colorArry.length(); i++) {
//gets each JSON object within the JSON array
JSONObject jsonObject = colorArry.getJSONObject(i);
// Retrieves the string labeled "colorName" and "hexValue",
// and converts them into javascript objects
String color = jsonObject.getString("colorName");
String hex = jsonObject.getString("hexValue");
// Adds strings from the current object to the data string
//spacing is included at the end to separate the results from
//one another
data += "\n"+ "Color Number " + (i + 1) + "\n"+"Color Name: " + color +
"\n"+ "nHex Value : " + hex + "nnn"+ "\n";
}
// Adds the data string to the TextView "results"
results.setText(data);
}
*/
// Try and catch are included to handle any errors due to JSON
catch (JSONException e) {
// If an error occurs, this prints the error to the log
e.printStackTrace();
}
}
},
// The final parameter overrides the method onErrorResponse() and passes VolleyError
//as a parameter
new Response.ErrorListener() {
@Override
// Handles errors that occur due to Volley
public void onErrorResponse(VolleyError error) {
Log.e("Volley", "Error");
}
}
);
// Adds the JSON array request "arrayreq" to the request queue
requestQueue.add(arrayreq);
}}
那么我如何在列表视图中显示我的截击响应而不是textview（按预期显示响应） 在同一视图中有textview和listview被认为是错误的吗？ 如果我这样做：myAdapter.add（结果），应用程序崩溃。你说除了获取列表并将适配器设置为该列表之外我不需要任何其他内容。
答案 0 :(得分：0)
我认为你不太了解Adapters的主要功能。让我向你解释一下：
ArrayAdapter类是Adapter（从BaseAdapter扩展而来），与Arrays和Lists一起使用，您可以在不使用的情况下使用它必须手动调用getView()方法。要使它工作，您需要在创建过程中传递3个参数：
1 - 您的context
2 - 列表每行的Layout
3 - 您的数据采用List或Array格式
<强>例如
adapter=new ArrayAdapter(this, R.layout.item_layout, items);
在这种情况下，Android本身会检查列表的大小，获取所有数据并在视图的每一行中输入，然后以列表形式返回给您。
您担心的getView()方法属于ArrayAdapter超类（BaseAdapter）并且由应用自动管理，因此请不要担心。在将列表传递给适配器之前，请记住检查列表是否为空或为空。