如何将TextInputLayout输入存入SharedPreferences并在其他Activity展示？解决空指针异常

核心崩溃原因 #

报错NullPointerException: Attempt to invoke virtual method 'android.widget.EditText com.google.android.material.textfield.TextInputLayout.getEditText()' on a null object reference，本质是你调用findViewById获取的TextInputLayout对象为null，后续调用getEditText()自然触发空指针。

导致TextInputLayout为null的两个关键问题：

1. RegistrationActivity的onCreate中未加载布局：你完全漏掉了setContentView(R.layout.你的注册页面布局ID)，没有加载布局时，所有findViewById都会返回null。
2. ID匹配错误：你用的R.id.TextInputEditText、R.id.PasswordInputEditText大概率是布局中内部EditText的ID，而非外层TextInputLayout的ID，用EditText的ID找TextInputLayout肯定找不到。

分步修复 #

1. 补全布局加载代码

在RegistrationActivity的onCreate开头，先调用setContentView加载你的注册页面布局，示例：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_registration); // 必须先加载布局
    // 后续SharedPreferences、findViewById代码...
}

2. 修正ID匹配

打开你的注册页面布局文件（比如activity_registration.xml），确认TextInputLayout的ID，示例布局结构：

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/til_name" <!-- 这是TextInputLayout的ID -->
    ...>
    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/TextInputEditText" <!-- 这是内部EditText的ID -->
        .../>
</com.google.android.material.textfield.TextInputLayout>

然后在代码中用TextInputLayout的ID来findViewById：

// 替换成你布局中TextInputLayout的实际ID
TextInputLayout nameField = findViewById(R.id.til_name);
TextInputLayout passwordField = findViewById(R.id.til_password);
TextInputLayout phoneField = findViewById(R.id.til_phone);

3. 增加空值安全判断（可选但推荐）

为了避免后续潜在的空指针，建议在调用getEditText()前先判断TextInputLayout是否为空：

if (nameField != null && nameField.getEditText() != null) {
    nameField.getEditText().setText(na);
}

4. 优化：使用ViewBinding替代findViewById

ViewBinding能彻底避免ID匹配错误，还能简化代码，步骤如下：

• 在模块的build.gradle中启用ViewBinding：

android {
    ...
    buildFeatures {
        viewBinding true
    }
}

• 修改RegistrationActivity的代码：

private ActivityRegistrationBinding binding;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    binding = ActivityRegistrationBinding.inflate(getLayoutInflater());
    setContentView(binding.getRoot());

    SharedPreferences file = getSharedPreferences("userData", MODE_PRIVATE);
    String na = file.getString("name", "");
    String pas = file.getString("password2", "");
    String ph = file.getString("phone", "");

    // 直接通过binding访问TextInputLayout，无需findViewById
    if (binding.tilName.getEditText() != null) {
        binding.tilName.getEditText().setText(na);
    }
    if (binding.tilPassword.getEditText() != null) {
        binding.tilPassword.getEditText().setText(pas);
    }
    if (binding.tilPhone.getEditText() != null) {
        binding.tilPhone.getEditText().setText(ph);
    }
}

public void confirmInput(View v) {
    SharedPreferences file = getSharedPreferences("userData", MODE_PRIVATE);
    SharedPreferences.Editor editor = file.edit();

    String name = "";
    if (binding.tilName.getEditText() != null) {
        name = binding.tilName.getEditText().getText().toString();
    }
    String password2 = "";
    if (binding.tilPassword.getEditText() != null) {
        password2 = binding.tilPassword.getEditText().getText().toString();
    }
    String phone = "";
    if (binding.tilPhone.getEditText() != null) {
        phone = binding.tilPhone.getEditText().getText().toString();
    }

    editor.putString("name", name);
    editor.putString("password2", password2);
    editor.putString("phone", phone);
    editor.apply(); // 推荐用apply()替代commit()，异步更高效

    Intent in = new Intent(this, LoginActivity.class);
    startActivity(in);
}

为什么之前用EditText正常？ #

因为你之前直接findViewById的是EditText的ID，且当时的Activity中正确调用了setContentView，所以能找到EditText对象；换成TextInputLayout后，既没加载布局，又用错了ID，才导致空指针崩溃。

内容的提问来源于stack exchange，提问作者Nutshoot12