Android Studio - 如果按下按钮且文本框中没有文本，则显示一个字符串，输入文本时显示另一个字符串

Question

I am incredibly new to Android Studio and was hoping to get some assistance. For some reason, this code is only displaying the ("Hi, " +name) portion. I am not sure what I am doing wrong or how to get the ("You must enter a name") portion to show when there is no text that has been inputted. We are needing to incorporate a SayHello() function into this and I am not sure if I am doing it properly... enter image description here

package com.example.assignment5_2;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    EditText nameText;
    TextView textGreeting;
    Button buttonSayHello;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        nameText = (EditText) findViewById(R.id.nameText);
        textGreeting = (TextView) findViewById(R.id.textGreeting);
        buttonSayHello = (Button) findViewById(R.id.buttonSayHello);

        buttonSayHello.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SayHello();
            }

            public void SayHello() {
                String name = nameText.getText().toString();
                if (name != null) {
                    textGreeting.setText("Hi, " + name);
                } else {
                    textGreeting.setText("You must enter a name");
                    buttonSayHello.setEnabled(name.isEmpty());
                }

            }
        });
    }
} 

Answer 1

Hey I've tried your code and I guess I found the issue, please alter your condition as follows:

 public void SayHello() {
                String name = nameText.getText().toString();
                if (!name.isEmpty()) {
                    textGreeting.setText("Hi, " + name);
                } else {
                    textGreeting.setText("You must enter a name");
                }

It is preferred to use .isEmpty() method to check if the string is empty or not instead of using,= null or == null, by altering your condition like I mentioned above your empty EditText check will work too. Check screenshots below for both cases:

try this and do let me know if it works !!

Answer 2

I think I got your problem, in the SayHello you have to change if(name != null) to

if(.name.trim().equals("")) or if(name.trim().length > 0

Hope this helps