Question

应用程序的快速概述：用户从列表中选择一个朋友，该朋友显示在微调器中。输入消息后，用户单击发送按钮。这就是应用程序崩溃的地方。

这是logcat的相关输出：

java.lang.ClassCastException：java.lang.String无法强制转换为com.parse.ParseUser at com.teamtreehouse.ribbit.SMSActivity.createMessage（SMSActivity.java:113） at com.teamtreehouse.ribbit.SMSActivity $ 1.onClick（SMSActivity.java:49）

这是相关代码：

ParseUser RecipientName = (ParseUser)friendsList.getSelectedItem();

// some other code

ParseObject message = new ParseObject(ParseConstants.CLASS_SMS);
message.put(ParseConstants.KEY_SENDER_NAME, RecipientName.getCurrentUser().getUsername());
//some other code

有什么想法吗？

完整性的完整代码：

public class SMSActivity extends Activity {
   protected ParseRelation<ParseUser> mFriendsRelation;
   protected ParseUser mCurrentUser;
   protected List<ParseUser> mFriends;
   protected Button sendButton;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sms);
}

public void onResume() {
    super.onResume();

    sendButton = (Button)findViewById(R.id.send_message_button);

    sendButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            ParseObject message = createMessage();
            if (message == null) {
                AlertDialog.Builder builder = new AlertDialog.Builder(SMSActivity.this);
                builder.setMessage(R.string.error_sending_file).
                setTitle(R.string.general_error).setPositiveButton(android.R.string.ok, null);
                AlertDialog dialog = builder.create();
                dialog.show();
            }
            else {
                send(message);
            }
            finish();
        }
    });

    mCurrentUser = ParseUser.getCurrentUser();
    mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

    //get a list of all the friends of the user
    ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
    query.addAscendingOrder(ParseConstants.KEY_USERNAME);
    query.findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> friends, ParseException e) {


            if (e == null) {
                mFriends = friends;

                String[] usernames = new String[mFriends.size()];
                int i = 0;
                for (ParseUser user : mFriends) {
                    usernames[i] = user.getUsername();
                    i++;
                }

                //attach the friendlist to the spinner
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                        SMSActivity.this,
                        android.R.layout.simple_spinner_dropdown_item,
                        usernames);

                Spinner friendsList = (Spinner) findViewById(R.id.friends_list);
                friendsList.setAdapter(adapter);



            } else {
                AlertDialog.Builder builder = new AlertDialog.Builder(SMSActivity.this);
                builder.setMessage(e.getMessage())
                        .setTitle(R.string.error_title)
                        .setPositiveButton(android.R.string.ok, null);
                AlertDialog dialog = builder.create();
                dialog.show();
            }

        }
    });
}

protected ParseObject createMessage() {
    EditText messageView = (EditText)findViewById(R.id.message_body);
    String messageContent = messageView.getText().toString();

    Spinner friendsList = (Spinner) findViewById(R.id.friends_list);

    ParseUser RecipientName = (ParseUser)friendsList.getSelectedItem();




    ParseObject message = new ParseObject(ParseConstants.CLASS_SMS);
    message.put(ParseConstants.KEY_SENDER_ID, ParseUser.getCurrentUser().getObjectId());
    message.put(ParseConstants.KEY_SENDER_NAME, RecipientName.getCurrentUser().getUsername());
    message.put(ParseConstants.KEY_RECIPIENT_IDS,
            ((ParseUser) friendsList.getSelectedItem()).getObjectId());
    message.put(ParseConstants.KEY_SMS, messageContent);

    return message;
}

protected void send(ParseObject message) {
    message.saveInBackground(new SaveCallback() {
        @Override
        public void done(ParseException e) {
            if (e == null) {
                //success
                Toast.makeText(SMSActivity.this, R.string.success_message,Toast.LENGTH_SHORT);
            }

            else {
                AlertDialog.Builder builder = new AlertDialog.Builder(SMSActivity.this);
                builder.setMessage(e.getMessage())
                        .setTitle(R.string.error_title)
                        .setPositiveButton(android.R.string.ok, null);
                AlertDialog dialog = builder.create();
                dialog.show();
            }


        }
    });

}

}

Answer 1

创建一个Map <String,ParseUser> map = new HashMap<String,ParseUser>() ...在这里你可以填写这张map.like

for (ParseUser user : mFriends) {
                    usernames[i] = user.getUsername();
                    map.put(user.getUsername(),user);
                    i++;
                }

现在就像：

ParseUser RecipientName = map.get(friendsList.getSelectedItem());

java.lang.ClassCastException：java.lang.String无法强制转换为com.parse.ParseUser

1 个答案: