我在使用 Android 中的 RecyclerView 时遇到一些问题。当我运行该项目时，没有显示，只有白屏。请帮助..
主要 Activity 代码:
public class MainActivity extends AppCompatActivity {
RecyclerView mRecyclerView;
private RecyclerView.LayoutManager mLayoutManager;
private MyAdapter mViewAdapter;
List<News> news_list = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new ParseNewsJSON().execute();
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
mRecyclerView.setHasFixedSize(true);
//mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
mViewAdapter= new MyAdapter(news_list);
mRecyclerView.setAdapter(mViewAdapter);
}
}
我的适配器代码:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private List<News> newsArticleList;
public class ViewHolder extends RecyclerView.ViewHolder{
public TextView title;
//description, genre;
public ViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.textView_articleHeading);
// description = (TextView) itemView.findViewById(R.id.textView_description);
// image = (TextView) itemView.findViewById(R.id.rating);
}
}
public MyAdapter (List<News> newsArticleList){
this.newsArticleList = newsArticleList;
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.content_main, parent, false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(MyAdapter.ViewHolder holder, int position) {
News news = newsArticleList.get(position);
holder.title.setText(news.getHeading());
}
@Override
public int getItemCount() {
return newsArticleList.size();
}
}
JSON 解析代码:
public class ParseNewsJSON extends AsyncTask<String, Void, String> {
private final String JSON_URL = "https://newsapi.org/v2/top-headlines?sources=cnn&apiKey=c80ddd850a524fe5975cad881d6f4aba";
String result ="";
ArrayList<String> article_heading = new ArrayList<>();
@Override
protected String doInBackground(String... strings) {
try {
URL url = new URL(JSON_URL);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(inputStream);
int data = reader.read();
while(data !=-1){
char current = (char) data;
result += current;
data = reader.read();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
@Override
protected void onPostExecute(String s) {
try {
JSONObject jsonObject = new JSONObject(result);
JSONArray jsonArray = jsonObject.getJSONArray("articles");
for(int i = 0; i<jsonArray.length(); i++){
News news = new News();
news.setHeading(String.valueOf(article_heading.add(jsonArray.getJSONObject(i).optString("title"))));
// article_heading.add(jsonArray.getJSONObject(i).optString("title"));
Log.d("news_JSON", article_heading.toString());
Log.d("news", news.getHeading().toString());
//article_heading.add(jsonArray.getJSONObject(i).optString("title"));
}
} catch (JSONException e) {
e.printStackTrace();
}
super.onPostExecute(s);
}
}
新闻.Java:
public class News {
private String heading;
//private String descrpiton;
private String img;
public String getHeading() {
return heading;
}
public void setHeading(String heading) {
this.heading = heading;
}
public String getImg() {
return img;
}
public void setImg(String img) {
this.img = img;
}
}
我已经阅读了一些主题，但是它们没有解决我的问题 This is the output when I run the emulator
activity_main.xml:
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.v7.widget.RecyclerView
android:layout_height="match_parent"
android:layout_width="match_parent"
android:id="@+id/recyclerView"
xmlns:android="http://schemas.android.com/apk/res/android">
</android.support.v7.widget.RecyclerView>
card_layout.xml:
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view"
android:layout_width="match_parent"
android:layout_marginTop="15dp"
android:layout_height="200dp"
app:cardCornerRadius="25dp"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<TextView
android:id="@+id/textView_articleHeading"
android:layout_marginLeft="5dp"
android:textStyle="bold"
android:textColor="#000000"
android:textSize="18sp"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<TextView
android:layout_height="0dp"
android:layout_width="match_parent"
android:layout_weight="1.0"
android:id="@+id/rating"
android:scaleType="center"
/>
<TextView
android:id="@+id/textView_description"
android:textSize="15sp"
android:textColor="#000000"
android:layout_marginBottom="5dp"
android:layout_marginLeft="5dp"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
最佳答案
我认为问题在于您没有将任何数据添加到您的 news_list ArrayList 检查您的 ParseNewsJSON onPostExecute() 方法
像下面的代码一样改变你的ParseNewsJSON
@Override
protected void onPostExecute(String s) {
try {
JSONObject jsonObject = new JSONObject(result);
JSONArray jsonArray = jsonObject.getJSONArray("articles");
for(int i = 0; i<jsonArray.length(); i++){
News news = new News();
news.setHeading(String.valueOf(article_heading.add(jsonArray.getJSONObject(i).optString("title"))));
// article_heading.add(jsonArray.getJSONObject(i).optString("title"));
Log.d("news_JSON", article_heading.toString());
Log.d("news", news.getHeading().toString());
news_list.add(news);
}
} catch (JSONException e) {
e.printStackTrace();
}
mViewAdapter= new MyAdapter(news_list);
mRecyclerView.setAdapter(mViewAdapter);
mViewAdapter.notifyDataSetChanged().
super.onPostExecute(s);
}
关于java - RecyclerView 不显示 - Android，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47918023/