Android 为什么'；活动中的findViewById（）是否返回用户键入的值？

我正在创建一个Android应用程序，其中场景是用户注册，单击“注册”按钮，该应用程序将数据发送到RESTAPI

活动\u注册\u登录.java

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/signUp"
        android:text="@string/sign_up"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/logIn"
        android:text="@string/log_in"
        app:layout_constraintStart_toEndOf="@+id/signUp" />

    <EditText
        android:id="@+id/password"
        android:inputType="textPassword"
        app:layout_constraintTop_toBottomOf="@+id/mobNum" />

    <EditText
        android:id="@+id/mobNum"
        app:layout_constraintTop_toBottomOf="@+id/countryCode" />


</android.support.constraint.ConstraintLayout>

    public class SignUpLogIn extends AppCompatActivity {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            final ConnectionStatus connectionStatus = new ConnectionStatus(getApplicationContext());
            if(!connectionStatus.isOnline()){
                connectionStatus.displayMobileDataSettingsDialog(this, getApplicationContext());
            }
            setContentView(R.layout.activity_sign_up_log_in);


            final TextView mobNumberTextView = (TextView) findViewById(R.id.mobNum);
            final TextView passwordTextView = (TextView) findViewById(R.id.password);
            Button signUp = (Button) findViewById(R.id.signUp);


            final String mobNumber = mobNumberTextView.getText().toString();
            final String password = passwordTextView.getText().toString();

            signUp.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(!validateInputFields(mobNumber, password)){
                        Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                        checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                        checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                        checkSignUpStatusIntent.putExtra("confirmPassword", password);
                        startService(checkSignUpStatusIntent);
                        connectionStatus.showProgress();
                    }
                }
            });
        }

private boolean validateInputFields(String mobNum, String password){
        StringBuffer errors = new StringBuffer();
        int count = 0;
        boolean hasError = false;
        if(mobNum == null || mobNum.isEmpty()){
            ++count;
            errors.append(count + ") Please enter your mobile number");
            errors.append('\n');
            hasError = true;
        }
        if(password == null || password.isEmpty()){
            //cEmail field is empty
            ++count;
            errors.append(count + ") Please enter a password");
            errors.append('\n');
            hasError = true;
        }
        if(hasError){
            Toast.makeText(this, errors.toString(), Toast.LENGTH_LONG).show();
            return true;
        }
        return false;
    }

在onClick（）中，值为空，尽管用户输入了值

为什么呢

如何修复它

请在线回答

附言：

---

我无法删除上面

.setOnClickListener

---

您需要从

onClick（）方法中获取
mobNumber
和
password
：

    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

    String mobNumber = mobNumberTextView.getText().toString();
    String password = passwordTextView.getText().toString();

            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });

编辑
如果您像这样使用变量，则无需将其声明为final

  TextView mobNumberTextView = (TextView) findViewById(R.id.mobNum);
  TextView passwordTextView = (TextView) findViewById(R.id.password);

和内部
onClick（）

编辑2
我刚发现你的问题

在validateInputFields方法中，您正在传递两个字符串，mobNum和password，在if语句中，您正在尝试向该方法传递两个字符串，这没关系，
if（！validateInputFields（mobNumber，password））…
但是，您试图通过该方法传递的两个字符串在
onClick（）之外，无法达到这些值，并且您的
validateInputFields（）
方法无法工作

编辑3
我只是看到您的xml中有这两个EditText

 <EditText
        android:id="@+id/password"
        android:inputType="textPassword"
        app:layout_constraintTop_toBottomOf="@+id/mobNum" />

    <EditText
        android:id="@+id/mobNum"
        app:layout_constraintTop_toBottomOf="@+id/countryCode" />

您应该在xml中添加两个文本视图，或者将
TextView mobNum….
更改为

EditText mobNumber...

像这样

 EditText mobNumberTextView = (EditText) findViewById(R.id.mobNum);
 EditText passwordTextView = (EditText) findViewById(R.id.password);

您必须在onClick中获得值

为什么？

findViewById
用于绑定视图，绑定后您会立即调用
getText
，这就是为什么它是空的

用这个替换你的代码

    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String mobNumber = mobNumberTextView.getText().toString();
            String password = passwordTextView.getText().toString();

            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });

请从onClickListener中的EditText获取值

    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final String mobNumber = mobNumberTextView.getText().toString();
            final String password = passwordTextView.getText().toString();
            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });

您需要从
注册中的
edittext
获取值。setOnClickListener

    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

             String mobNumber = mobNumberTextView.getText().toString();
             String password = passwordTextView.getText().toString();

            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });

单击后，
onClick
中不再需要final字样！对…没有必要做最后的决定。如果在内部类中使用，我们必须使外部类变量为final。@VishalChhodwani我得到的变量“mobNumberTextView”是从内部类中访问的，如果我删除setOnClickListener外部变量的final，则需要声明为final。@SpandanaKrishnan我刚刚更新了答案。无需声明变量final。我得到的
变量“mobNumberTextView”是从内部类中访问的，如果我删除setOnClickListener外部变量的final，则需要声明为final
。但是，在用户输入值之前是否将变量mobNumberTextView设为final，因此它总是空的？？您可以从onClick中删除final，也可以从您的文本视图中删除final，没有必要保留它们。我无法为文本视图删除final。您可以编辑您的问题并让我们知道您在哪里使用这些final变量吗？
    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final String mobNumber = mobNumberTextView.getText().toString();
            final String password = passwordTextView.getText().toString();
            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });

    signUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

             String mobNumber = mobNumberTextView.getText().toString();
             String password = passwordTextView.getText().toString();

            if(!validateInputFields(mobNumber, password)){
                Intent checkSignUpStatusIntent = new Intent(getApplicationContext(), CrossCheckSignUpService.class);
                checkSignUpStatusIntent.putExtra("countryCode", countryCode);
                checkSignUpStatusIntent.putExtra("confirmMobileNumber", mobNumber);
                checkSignUpStatusIntent.putExtra("confirmPassword", password);
                startService(checkSignUpStatusIntent);
                connectionStatus.showProgress();
            }
        }
    });