Question

注册活动是开始活动。单击文本视图，它应更改为登录活动，但应用程序在执行时崩溃。 ................................................... ................................................... ................................................... ................................................... ................................................... ................................................... ................................................... ................................................... .........................................

注册活动

package com.example.saiteja.traffic_sway;

import android.app.ProgressDialog;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.google.firebase.auth.FirebaseAuth;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;


public class RegisterActivity extends AppCompatActivity implements View.OnClickListener {

private TextView loginTV;
private EditText email;
private EditText password;
private Button regButton;
private FirebaseAuth mAuth;
private ProgressDialog progressDialog;

@Override

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);

    mAuth = FirebaseAuth.getInstance();
    if (mAuth.getCurrentUser() != null) {
        //that means user is already logged in
        //so close this activity
        finish();

        //and open profile activity
        startActivity(new Intent(RegisterActivity.this, LoginActivity.class));
    }
    email = (EditText) findViewById(R.id.editText);
    password = (EditText) findViewById(R.id.editText2);
    loginTV = (TextView) findViewById(R.id.loginTV);

    regButton = (Button) findViewById(R.id.button);

    progressDialog = new ProgressDialog(this);

    loginTV = (TextView) findViewById(R.id.loginTV);
    regButton.setOnClickListener(this);
    loginTV.setOnClickListener(this);
}
@Override
public void onClick(View view) {

    if(view == regButton){
        registerUser();
    }

    if(view == loginTV){
        //open login activity when user taps on the already registered textview
        Intent i = new Intent(RegisterActivity.this, LoginActivity.class);
        startActivity(i);
    }

}

private void registerUser() {

    //getting email and password from edit texts
    String email1 = email.getText().toString().trim();
    String password1 = password.getText().toString().trim();

    //checking if email and passwords are empty
    if (TextUtils.isEmpty(email1)) {
        Toast.makeText(this, "Please enter email", Toast.LENGTH_LONG).show();
        return;
    }

    if (TextUtils.isEmpty(password1)) {
        Toast.makeText(this, "Please enter password", Toast.LENGTH_LONG).show();
        return;
    }

    //if the email and password are not empty
    //displaying a progress dialog

    progressDialog.setMessage("Registering Please Wait...");
    progressDialog.show();

    //creating a new user
    mAuth.createUserWithEmailAndPassword(email1, password1)
            .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    //checking if success
                    if (task.isSuccessful()) {
                        finish();
                        startActivity(new Intent(getApplicationContext(), MainActivity.class));
                    } else {
                        //display some message here
                        Toast.makeText(RegisterActivity.this, "Registration Error", Toast.LENGTH_LONG).show();
                    }
                    progressDialog.dismiss();
                }
            });

}

}

登录活动

package com.example.saiteja.traffic_sway;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

  public class LoginActivity extends AppCompatActivity {
private TextView registerTV;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    registerTV = (TextView)findViewById(R.id.loginTV);
    registerTV.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(LoginActivity.this,RegisterActivity.class));
        }
    });
}

}

Android Manifest.xml

<?xml version="1.0" encoding="utf-8"?>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".RegisterActivity"
        android:screenOrientation="sensorPortrait"
        android:label="Traffic Sway">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".MainActivity"/>
    <activity android:name=".Main2Activity" />
    <activity android:name=".LoginActivity"/>
</application>

单击“已有用户？登录”文本View.pls帮助时，应用程序崩溃

Answer 1

在启动finish()之前，请勿调用Activity函数。祝您申请顺利。

Answer 2

问题似乎是您的LoginActivity中的findViewById

registerTV = (TextView)findViewById(R.id.loginTV);

检查 loginTV 是否在您的 activity_login.xml 中如果不是，那就是问题所在，一旦ID不可用， registerTV 将为空，并且您的registerTv.setOnclickListener()将无法正常工作。

更改活动时应用崩溃。该怎么办？

2 个答案: