我是新来的android和最近我试图从firebase提取数据到recyclerview/cardview显示垂直布局的数据,它显示的错误转换HashMap来ArrayList中,其中的代码是:java.util.HashMap不能转换为java.util.ArrayList
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
new GetDataFromFirebase().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
// Read from the database
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("0XtzzDme");
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
ArrayList<String> values = (ArrayList<String>) dataSnapshot.getValue();
recyclerView.setAdapter(new RecyclerViewAdapter(values));
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
System.out.println("Failed to read value." + error.toException());
}
});
}
和recyclerviewadapter
class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
private ArrayList<String> values;
RecyclerViewAdapter(ArrayList<String> values) {
this.values = values;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_view_item,parent,false));
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.name.setText(values.get(position));
}
@Override
public int getItemCount() {
return values.size();
}
class ViewHolder extends RecyclerView.ViewHolder {
private TextView name;
ViewHolder(View itemView) {
super(itemView);
name = (TextView) itemView.findViewById(R.id.list_item_text);
}
}
}
因为他们不能,他们是不一样的数据类型。一个是Map,另一个是List – AxelH
这里没有任何hashmap的代码,这就是为什么我在这里发布的问题 – user3921943
@ user3921943;这才是重点。 'dataSnapshot.getValue()'在你试图将它作为'ArrayList'处理时返回'HashMap'。这就像说你买了一只鸟,而它实际上是一头牛;它不会工作... – 0xDEADC0DE