recyclerView中发生错误
[英]Error occur in recyclerView
问题描述
This app is getting data directly from API. 
此应用程序直接从API获取数据。 When it goes to run such type of error occurs. 当它运行时，会发生此类错误。 Basically I think the error occurs in the getItemCount() method but i'm not be able to resolve the problem. 基本上，我认为该错误发生在getItemCount（）方法中，但我无法解决问题。 I've attached the error file and the whole code.I shall be thankful if you can resolve the error. 我已经附上了错误文件和整个代码。如果您能解决错误，请多谢。
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at com.techbrightsoft.database.MyRecyler.getItemCount(MyRecyler.java:36) at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3603) at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:3103) at android.view.View.measure(View.java:20151) at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:934) at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:973) at android.view.View.measure(View.java:20151) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6330) at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:20151) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6330) at android.support.v7.widget.Act
public class MyRecyler extends RecyclerView.Adapter<MyRecyler.MyHolder> {
private Context context;
private ArrayList<String> names;
public MyRecyler(Context context, ArrayList<String> names) {
this.context = context;
this.names = names;
}
@Override
public MyHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(this.context);
View view = inflater.inflate(R.layout.names, parent, false);
return new MyHolder(view);
}
@Override
public void onBindViewHolder(MyHolder holder, int position) {
holder.name.setText(this.names.get(position));
}
@Override
public int getItemCount() {
return names.size();
}
public class MyHolder extends RecyclerView.ViewHolder {
TextView name;
public MyHolder(View itemView) {
super(itemView);
name = itemView.findViewById(R.id.name);
}
}
public class MainActivity extends AppCompatActivity {
public static ArrayList<String> authors_names ;
RecyclerView recyclerView;
EditText editText;
Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recyclerView);
// Downloading Data From Internet
DownloadingData downloadingData = new DownloadingData();
downloadingData.execute("https://newsapi.org/v1/articles?source=the-next-web&sortBy=latest&apiKey=a301a9e90c774b4ebf7eb21000cdbdef");
// RecyclerView Set
MyRecyler recyler = new MyRecyler(MainActivity.this,authors_names);
recyclerView.setAdapter(recyler);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyler.notifyDataSetChanged();
}
}
1 个解决方案
解决方案1
0 2018-03-02 18:50:14
It seems this code does not properly initialize authors_names . 似乎此代码未正确初始化authors_names 。 If I have guess your code logic correctly, you want to fill authors_names with result from downloadingData . 如果我猜对了您的代码逻辑，那么您想用downloadingData结果填充authors_names 。 Generally, passing that list to your adapter is a bad practice. 通常，将该列表传递给适配器是一种不好的做法。
My suggestion is initializing names with an empty list and define a addAll() method for updating its content. 我的建议是用一个空列表初始化names ，并定义一个addAll()方法来更新其内容。 A simple and unoptimized implementation will be like this: 一个简单且未经优化的实现将是这样的：
private ArrayList<String> names = new ArrayList<>();
public void addAll(ArrayList<String> items) {
names.clear();
names.addAll(items);
notifyDatasetChanged();
}
And you need to add items with addAll() method from main code when downloadingData finished its job(normally through an callback). 而且，当downloadingData完成其工作时（通常通过回调），您需要从主代码中使用addAll()方法添加项目。
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