我们已经看到使用Back4App在Android中实现用户注册。在那篇文章中,我们已经在我们的应用程序中实现了用户注册。在本文中,我们将研究Android应用程序中用户登录的实现。
我们将在本文中构建什么?
我们将构建一个简单的应用程序,在该应用程序中,我们将在Android App中显示用户登录表单,并使用该登录表单允许用户在应用程序内部登录。下面提供了一个示例视频,以使您对本文中的工作有个大概的了解。注意,我们将使用Java语言实现该项目。
分步实施
本文是使用Back4App在Android中进行用户注册的延续。
步骤1:使用activity_main.xml文件
导航到应用程序> res>布局> activity_main.xml,然后将以下代码添加到该文件中。以下是activity_main.xml文件的代码。
XML
XML
Java
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.parse.ParseUser;
public class HomeActivity extends AppCompatActivity {
// creating a variable
// for our text view..
private TextView userNameTV;
// button for logout
private Button logoutBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
logoutBtn = findViewById(R.id.idBtnLogout);
// initializing our variables
userNameTV = findViewById(R.id.idTVUserName);
// getting data from intent.
String name = getIntent().getStringExtra("username");
// setting data to our text view.
userNameTV.setText(name);
// initializing click listener for logout button
logoutBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// calling a method to logout our user.
ParseUser.logOutInBackground(e -> {
if (e == null) {
Toast.makeText(HomeActivity.this, "User Logged Out", Toast.LENGTH_SHORT).show();
Intent i = new Intent(HomeActivity.this, MainActivity.class);
startActivity(i);
finish();
}
});
}
});
}
}
Java
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.parse.ParseUser;
public class MainActivity extends AppCompatActivity {
// creating variables for our edit text and buttons.
private EditText userNameEdt, passwordEdt;
private Button loginBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// initializing our edit text and buttons.
userNameEdt = findViewById(R.id.idEdtUserName);
passwordEdt = findViewById(R.id.idEdtPassword);
loginBtn = findViewById(R.id.idBtnLogin);
// adding on click listener for our button.
loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// on below line we are getting data from our edit text.
String userName = userNameEdt.getText().toString();
String password = passwordEdt.getText().toString();
// checking if the entered text is empty or not.
if (TextUtils.isEmpty(userName) && TextUtils.isEmpty(password)) {
Toast.makeText(MainActivity.this, "Please enter user name and password", Toast.LENGTH_SHORT).show();
}
// calling a method to login our user.
loginUser(userName, password);
}
});
}
private void loginUser(String userName, String password) {
// calling a method to login a user.
ParseUser.logInInBackground(userName, password, (parseUser, e) -> {
// after login checking if the user is null or not.
if (parseUser != null) {
// if the user is not null then we will display a toast message
// with user login and passing that user to new activity.
Toast.makeText(this, "Login Successful ", Toast.LENGTH_SHORT).show();
Intent i = new Intent(MainActivity.this, HomeActivity.class);
i.putExtra("username", userName);
startActivity(i);
} else {
// display an toast message when user logout of the app.
ParseUser.logOut();
Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();
}
});
}
}
第2步:创建新活动以在注册后重定向我们的用户
导航到应用程序> Java >应用程序的包名称>右键单击它>新建>空活动,并将其命名为HomeActivity 。或者您也可以参考本文“如何在Android Studio中创建新活动”?
步骤3:使用activity_home.xml文件
导航至应用程序> res>布局> activity_home.xml文件,然后将以下代码添加到其中。
XML格式
步骤4:使用HomeActivity。 Java文件
导航到应用程序> Java >您的应用程序的程序包名称> HomeActivity。 Java文件,并向其中添加以下代码。在代码内部添加了注释,以更详细地了解代码。
Java
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.parse.ParseUser;
public class HomeActivity extends AppCompatActivity {
// creating a variable
// for our text view..
private TextView userNameTV;
// button for logout
private Button logoutBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
logoutBtn = findViewById(R.id.idBtnLogout);
// initializing our variables
userNameTV = findViewById(R.id.idTVUserName);
// getting data from intent.
String name = getIntent().getStringExtra("username");
// setting data to our text view.
userNameTV.setText(name);
// initializing click listener for logout button
logoutBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// calling a method to logout our user.
ParseUser.logOutInBackground(e -> {
if (e == null) {
Toast.makeText(HomeActivity.this, "User Logged Out", Toast.LENGTH_SHORT).show();
Intent i = new Intent(HomeActivity.this, MainActivity.class);
startActivity(i);
finish();
}
});
}
});
}
}
步骤5:使用MainActivity。 Java文件
转到MainActivity。 Java文件并参考以下代码。下面是MainActivity的代码。 Java文件。在代码内部添加了注释,以更详细地了解代码。
Java
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.parse.ParseUser;
public class MainActivity extends AppCompatActivity {
// creating variables for our edit text and buttons.
private EditText userNameEdt, passwordEdt;
private Button loginBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// initializing our edit text and buttons.
userNameEdt = findViewById(R.id.idEdtUserName);
passwordEdt = findViewById(R.id.idEdtPassword);
loginBtn = findViewById(R.id.idBtnLogin);
// adding on click listener for our button.
loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// on below line we are getting data from our edit text.
String userName = userNameEdt.getText().toString();
String password = passwordEdt.getText().toString();
// checking if the entered text is empty or not.
if (TextUtils.isEmpty(userName) && TextUtils.isEmpty(password)) {
Toast.makeText(MainActivity.this, "Please enter user name and password", Toast.LENGTH_SHORT).show();
}
// calling a method to login our user.
loginUser(userName, password);
}
});
}
private void loginUser(String userName, String password) {
// calling a method to login a user.
ParseUser.logInInBackground(userName, password, (parseUser, e) -> {
// after login checking if the user is null or not.
if (parseUser != null) {
// if the user is not null then we will display a toast message
// with user login and passing that user to new activity.
Toast.makeText(this, "Login Successful ", Toast.LENGTH_SHORT).show();
Intent i = new Intent(MainActivity.this, HomeActivity.class);
i.putExtra("username", userName);
startActivity(i);
} else {
// display an toast message when user logout of the app.
ParseUser.logOut();
Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();
}
});
}
}
现在运行您的应用程序,并查看该应用程序的输出:
输出:
在以下链接上查看项目: https : //github.com/ChaitanyaMunje/GFG-Back4App/tree/LoginForm