您好我是Android编程的新手，并试图学习它。我按照this教程进行了操作，但是我不知道如何在列表视图中显示记录。
PostActivity.java文件来自以下教程，
package com.kylewbanks.gsonvolleytutorial;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
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.StringRequest;
import com.android.volley.toolbox.Volley;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import static android.R.id.list;
public class PostActivity extends Activity {
private static final String ENDPOINT = "https://kylewbanks.com/rest/posts.json";
private RequestQueue requestQueue;
private Gson gson;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_post);
requestQueue = Volley.newRequestQueue(getApplicationContext());
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setDateFormat("M/d/yy hh:mm a");
gson = gsonBuilder.create();
fetchPosts();
}
private void fetchPosts() {
StringRequest request = new StringRequest(Request.Method.GET, ENDPOINT, onPostsLoaded, onPostsError);
requestQueue.add(request);
}
private final Response.Listener<String> onPostsLoaded = new Response.Listener<String>() {
@Override
public void onResponse(String response) {
//Log.i(PostActivity.class.getSimpleName(), response);
List<Post> posts = Arrays.asList(gson.fromJson(response, Post[].class));
//Log.i(PostActivity.class.getSimpleName(), posts.size() + " posts loaded.");
List listview = (List) findViewById(R.id.postListView);
for (Post post : posts) {
//Log.i(PostActivity.class.getSimpleName(), post.ID + ": " + post.title);
}
ArrayAdapter adapter = new ArrayAdapter(this,R.layout.single_post_item, posts);
listview.setAdapter(adapter);
}
};
private final Response.ErrorListener onPostsError = new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e(PostActivity.class.getSimpleName(), error.toString());
}
};
}
Post.java
import java.util.Date;
import com.google.gson.annotations.SerializedName;
public class Post {
@SerializedName("id")
long ID;
@SerializedName("date")
Date dateCreated;
String title;
String author;
String url;
String body;
}
activity_post.xml
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".PostActivity">
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="@+id/postListView"
android:layout_alignParentBottom="true" />
</RelativeLayout>
single_post_item.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="TextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/textView" />
</LinearLayout>
更新错误1：
:app:processDebugManifest
:app:processDebugResources
AGPBI: {"kind":"error","text":"Error parsing XML: XML or text declaration not at start of entity","sources":[{"file":"C:\\Users\\xxx\\Downloads\\GSONVolleyTutorial-master\\GSONVolleyTutorial-master\\app\\src\\main\\res\\layout\\activity_post.xml","position":{"startLine":0}}],"original":"","tool":"AAPT"}
AGPBI: {"kind":"error","text":"Error parsing XML: XML or text declaration not at start of entity","sources":[{"file":"C:\\Users\\xxx\\Downloads\\GSONVolleyTutorial-master\\GSONVolleyTutorial-master\\app\\src\\main\\res\\layout\\single_post_item.xml","position":{"startLine":0}}],"original":"","tool":"AAPT"}
C:\Users\xxx\Downloads\GSONVolleyTutorial-master\GSONVolleyTutorial-master\app\build\intermediates\res\merged\debug\layout\activity_post.xml:1: error: Error parsing XML: XML or text declaration not at start of entity
C:\Users\xxx\Downloads\GSONVolleyTutorial-master\GSONVolleyTutorial-master\app\build\intermediates\res\merged\debug\layout\single_post_item.xml:1: error: Error parsing XML: XML or text declaration not at start of entity
FAILED
FAILURE: Build failed with an exception.
更新错误2：
C:\Users\xxx\Downloads\GSONVolleyTutorial-master\GSONVolleyTutorial-master\app\src\main\java\com\kylewbanks\gsonvolleytutorial\PostActivity.java:70: error: no suitable constructor found for ArrayAdapter(<anonymous Listener<String>>,int,int,List<String>)
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.single_post_item,R.id.textView, posts_strs);
^
constructor ArrayAdapter.ArrayAdapter(Context,int,int,String[]) is not applicable
(argument mismatch; <anonymous Listener<String>> cannot be converted to Context)
constructor ArrayAdapter.ArrayAdapter(Context,int,int,List<String>) is not applicable
(argument mismatch; <anonymous Listener<String>> cannot be converted to Context)
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error
:app:compileDebugJavaWithJavac FAILED
FAILURE: Build failed with an exception.
答案 0 :(得分：3)
由于列表布局中只有一个TextView，因此您打算显示单个项目
1。）创建一个String arraylist并向其添加元素
2.。）在创建适配器
时提及@+id/textView"作为第3个参数
ArrayAdapter(Context context, int resource, int textViewResourceId, List<T> objects)
public class PostActivity extends Activity {
private static final String ENDPOINT = "https://kylewbanks.com/rest/posts.json";
private RequestQueue requestQueue;
private Gson gson;
private List<String> posts_strs ;
// keep it here for later use in other methods
private List<Post> posts ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// code
// initialize list
posts_strs = new ArrayList<String>();
// code
}
private final Response.Listener<String> onPostsLoaded = new Response.Listener<String>() {
@Override
public void onResponse(String response) {
//Log.i(PostActivity.class.getSimpleName(), response);
posts = Arrays.asList(gson.fromJson(response, Post[].class));
//Log.i(PostActivity.class.getSimpleName(), posts.size() + " posts loaded.");
List listview = (List) findViewById(R.id.postListView);
for (Post post : posts) {
// add items to list
posts_strs.add( post.ID + ": " + post.title);
//Log.i(PostActivity.class.getSimpleName(), post.ID + ": " + post.title);
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(PostActivity.this,R.layout.single_post_item
,R.id.textView, posts_strs);
// use the textview id posts_strs while creating adapter
listview.setAdapter(adapter);
}
};
// code
}
问题：
1。）在<?xml version="1.0" encoding="utf-8"?>布局XML和activity_post
single_post_item
2.。）使用PostActivity.this代替this，因为this将引用匿名Response.Listener<String>类而不是PostActivity。
答案 1 :(得分：1)
C:\Users\xxx\Downloads\GSONVolleyTutorial-master\GSONVolleyTutorial-master\app\src\main\java\com\kylewbanks\gsonvolleytutorial\PostActivity.java:70: error: no suitable constructor found for ArrayAdapter(<anonymous Listener<String>>,int,int,List<String>)
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.single_post_item,R.id.textView, posts_strs);
^
constructor ArrayAdapter.ArrayAdapter(Context,int,int,String[]) is not applicable
(argument mismatch; <anonymous Listener<String>> cannot be converted to Context)
constructor ArrayAdapter.ArrayAdapter(Context,int,int,List<String>) is not applicable
(argument mismatch; <anonymous Listener<String>> cannot be converted to Context)
由于创建ArrayAdapter的代码位于匿名内部类中，因此this引用该匿名类的实例。要访问包含匿名类的this实例的PostActivity指针，请改用PostActivity.this。