android - 当有人没有在纯文本框中输入任何内容时，如何弹出错误消息？

Question

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

    btn_send_msg = (Button) findViewById(R.id.button13);
    input_msg = (EditText) findViewById(R.id.editText3);
    chat_conversation = (TextView) findViewById(R.id.textView4);

    user_name = getIntent().getExtras().get("user_name").toString();
    room_name = getIntent().getExtras().get("room_name").toString();
    setTitle("Room - " + room_name);

    root = FirebaseDatabase.getInstance().getReference().child(room_name);

    btn_send_msg.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Map<String, Object> map = new HashMap<String, Object>();
            temp_key = root.push().getKey();
            root.updateChildren(map);

            DatabaseReference message_root = root.child(temp_key);
            Map<String, Object> map2 = new HashMap<String, Object>();
            map2.put("name", user_name);
            map2.put("msg", input_msg.getText().toString());

            message_root.updateChildren(map2);

            input_msg.setText("");
        }
    });


    root.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            append_chat_conversation(dataSnapshot);
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

            append_chat_conversation(dataSnapshot);
        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}
private String chat_msg,chat_user_name;
private void append_chat_conversation(DataSnapshot dataSnapshot) {

    Iterator i = dataSnapshot.getChildren().iterator();

    while (i.hasNext()){

        chat_msg = (String) ((DataSnapshot)i.next()).getValue();
        chat_user_name = (String) ((DataSnapshot)i.next()).getValue();

        chat_conversation.append(chat_user_name + " - " + chat_msg + "\n");
    }
}

所以这个功能是针对聊天室的，所以我希望能够做到这一点，这样用户就可以向聊天室发送空白消息。所以我希望在用户尝试发送空白消息时发生错误。

谢谢!

Answer 1

检查输入文本并显示 toast 或您想要的任何内容。

 btn_send_msg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                Map<String, Object> map = new HashMap<String, Object>();
                temp_key = root.push().getKey();
                root.updateChildren(map);

                DatabaseReference message_root = root.child(temp_key);
                Map<String, Object> map2 = new HashMap<String, Object>();
                map2.put("name", user_name);
                map2.put("msg", input_msg.getText().toString());

                message_root.updateChildren(map2);

              String inputMsg= usernameEditText.getText().toString();
              if (inputMsg.matches("")) {
              Toast.makeText(this, "You did not enter a value", Toast.LENGTH_SHORT).show();
        return;
    }
            }
        });