在Android Studio中制作必填的EditText字段

<!-- activity_main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/editTextName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入姓名"
        android:inputType="text" />

    <Button
        android:id="@+id/buttonSubmit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="提交" />
</LinearLayout>

// MainActivity.java
public class MainActivity extends AppCompatActivity {

    private EditText editTextName;
    private Button buttonSubmit;

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

        editTextName = findViewById(R.id.editTextName);
        buttonSubmit = findViewById(R.id.buttonSubmit);

        buttonSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = editTextName.getText().toString().trim();
                if (name.isEmpty()) {
                    editTextName.setError("姓名是必填项");
                } else {
                    // 处理提交逻辑
                    Toast.makeText(MainActivity.this, "提交成功", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}