无法将java.util.arraylist强制转换为java.lang.object [] [英] java.util.arraylist cannot be cast to java.lang.object[]
问题描述
因此在下面的代码中,标有***的行为我提供了例外情况
So in my code below, line marked with *** gives me the exception
java.util.arraylist无法转换为java.lang.object []
java.util.arraylist cannot be cast to java.lang.object[]
我正在尝试从backendless检索用户列表.我创建了一个列表视图,该列表视图通常在添加到列表时可以使用.但在尝试获取响应(对象)时不可以
I am trying to retrieve a list of users from backendless. I have created a list view that works when normally adding to list. but not when trying to get the response(Object)
public class UserRolesActivity extends AppCompatActivity {
ListView userListView;
TextView changeRoleTv;
List<String> list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_user_roles);
userListView = (ListView) findViewById(R.id.usersListView);
list = new ArrayList<>();
changeRoleTv = (TextView) findViewById(R.id.chooseUserChangeTv);
Backendless.Data.mapTableToClass("Users", Users.class);
list.add("Name1");
list.add("Name2");
RetrieveUsers retrieveUsers = RetrieveUsers.getInstance();
retrieveUsers.getUsersAsync(new AsyncCallback<Object>() {
@Override
public void handleResponse(Object response) {
try{
*** Object [] result = (Object []) response; ***
List<Object> user = Arrays.asList(result);
for (int i = 0; i< user.size(); i++){
if (user.get(i) != null){
list.add(((Learner) user.get(i)).getFirstName().toString() + ": " + ((Learner) user.get(i)).getLastName().toString());
}
}
}catch (Exception e){
ShowToast(e.getMessage().toString());
}
userListView.setAdapter(new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, list));
}
@Override
public void handleFault(BackendlessFault fault) {
ShowToast(fault.getMessage());
}
});
}
private void ShowToast(String message)
{
Toast.makeText(this, message, LENGTH_LONG).show();
}
}
推荐答案
您正在做的事情看起来有点long:
what you are doing looks a bit long winded:
*** Object [] result = (Object []) response; ***
List<Object> user = Arrays.asList(result);
for (int i = 0; i< user.size(); i++){
if (user.get(i) != null){
list.add(((Learner) user.get(i)).getFirstName().toString() + ": " + ((Learner) user.get(i)).getLastName().toString());
}
}
可以压缩为:
List<?> users = (List<?>)response;
for (Object user : users) {
if (user != null){
// Some stuff
}
}
接下来,您将遇到以下问题:
Next you will get an issue with:
list.add(((Learner) user.get(i)).getFirstName().toString() + ": " + ((Learner) user.get(i)).getLastName().toString());
因为 user.get(i).getFirstName().toString()+:"
是一个字符串,然后将其强制转换为类型 Learner
.您将需要重新考虑这一点.
because user.get(i)).getFirstName().toString() + ": "
is a String which you are then casting to Type Learner
. You will need to rethink this.
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