安卓 Firebase 实时数据库的用户认证和 CRUD 操作
Firebase 是谷歌的一款著名产品，被如此多的开发者用来为他们的网站和应用添加后端功能。Firebase 将使后端数据库和处理数据库的工作变得更加容易。在本文中，我们将了解一下 Firebase 实时数据库在安卓系统中的实现。在本文中，我们将在我们的应用程序中添加电子邮件和密码验证，同时，我们将使用 Firebase 实时数据库在我们的应用程序中执行 CRUD(创建、读取、更新和删除)操作。
https://www.youtube.com/watch?v=-Gvpf8tXpbc
本文我们将构建什么？
在本文中，我们将构建一个简单的安卓应用程序，首先用用户的电子邮件和密码对其进行身份验证。之后，我们将在回收器视图中显示极客上可供极客使用的课程列表。我们将能够在这些课程上执行 CRUD 操作。下面是视频，我们将在其中看到我们将在本文中构建的内容。
[https://media.geeksforgeeks.org/wp-content/uploads/20210730113812/20210730_112523.mp4](https://media.geeksforgeeks.org/wp-content/uploads/20210730113812/20210730_112523.mp4)分步实施
第一步:创建新项目
要在安卓工作室创建新项目，请参考如何在安卓工作室创建/启动新项目。注意选择 Java 作为编程语言。
第二步:将你的应用连接到 Firebase
创建新项目后，导航到顶部栏上的“工具”选项。点击火焰基地。点击 Firebase 后，你可以看到截图中下面提到的右栏。
在该列中，导航到 Firebase 实时数据库。点击那个选项，你会看到两个选项:连接应用程序到 Firebase 和添加 Firebase 实时数据库到你的应用程序。单击立即连接，您的应用程序将连接到 Firebase。之后点击第二个选项，现在你的应用程序连接到 Firebase。
将您的应用程序连接到 Firebase 后，您将看到下面的屏幕。
之后，验证 Firebase 实时数据库的依赖项已经添加到我们的 Gradle 文件中。现在导航到应用程序>渐变脚本，并在该文件中检查是否添加了以下依赖项。如果以下依赖项没有添加到您的 build.gradle 文件中。在依赖项部分添加以下依赖项。下面是完整的依赖项部分，其中有身份验证和数据库的依赖项。
dependencies {
implementation 'androidx.appcompat:appcompat:1.3.0'
implementation 'com.google.android.material:material:1.4.0'
// dependency for picasso for loading image from url
implementation 'com.squareup.picasso:picasso:2.71828'
implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
// dependency for firebase database.
implementation 'com.google.firebase:firebase-database:20.0.0'
implementation platform('com.google.firebase:firebase-bom:28.2.1')
// dependency for firebase authentication.
implementation 'com.google.firebase:firebase-auth'
testImplementation 'junit:junit:4.+'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}
添加此依赖项后，同步您的项目，现在我们可以创建我们的应用程序了。如果你想了解更多关于连接你的应用到 Firebase。请参考这篇文章，详细了解如何将 Firebase 添加到安卓应用程序中。
第三步:创建 4 个不同的空活动
导航到应用程序>您的应用程序的包名>右键单击它>新建>活动>选择空活动并创建一个新活动。下面是我们在创建新活动时必须通过的四个不同活动的名称。
- 添加课程活动:这个活动我们将用于添加新的课程。
- 编辑课程活动:本活动将用于编辑我们的课程以及删除我们的课程。
- 登录活动:该活动将用于现有用户登录的登录目的。
- 注册活动:该活动用于注册新用户。
MainActivity.java文件已经存在，我们将在循环查看中显示课程列表。
第 4 步:使用 AndroidManifest.xml 文件
导航至应用程序> AndroidManifest.xml 文件，并为其添加互联网权限。下面是 AndroidManifest.xml 文件的完整代码。在这个文件中，我们还将启动器活动更改为登录活动。代码中添加了注释，以便更详细地了解。
可扩展标记语言
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.gtappdevelopers.firebasecrudapp">
<!--permissions for internet-->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<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/Theme.FirebaseCrudApp">
<activity
android:name=".EditCourseActivity"
android:label="Edit Course" />
<activity
android:name=".AddCourseActivity"
android:label="Add Course" />
<activity
android:name=".RegisterActivity"
android:label="Register" />
<!--login activity is set as launcher activity-->
<activity android:name=".LoginActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity" />
</application>
</manifest>
第五步:更新 colors.xml 文件
导航至应用程序>RES>values>colors . XML并添加以下颜色。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:tools="http://schemas.android.com/tools">
<color name="purple_200">#296D98</color>
<color name="purple_500">#296D98</color>
<color name="purple_700">#296D98</color>
<color name="teal_200">#FF03DAC5</color>
<color name="teal_700">#FF018786</color>
<color name="black">#FF000000</color>
<color name="white">#FFFFFFFF</color>
<color name="black_shade_1">#0e2433</color>
<color name="black_shade_2">#1C4966</color>
<color name="black_shade_3">#22252D</color>
<color name="mtrl_textinput_default_box_stroke_color" tools:override="true">#296D98</color>
<color name="light_blue_shade_1">#296D98</color>
<color name="gray">#424242</color>
<color name="yellow">#ffa500</color>
<color name="dark_blue_shade">#0D2162</color>
<color name="dark_blue_shade_2">#17388E</color>
<color name="light_blue_shade">#12B2E6</color>
</resources>
第 6 步:更新我们的主题. xml 文件
导航至应用程序>RES>values>themes . XML并添加以下代码。
可扩展标记语言
<resources xmlns:tools="http://schemas.android.com/tools">
<!-- Base application theme. -->
<style name="Theme.FirebaseCrudApp" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
<!-- Primary brand color. -->
<item name="colorPrimary">@color/purple_500</item>
<item name="colorPrimaryVariant">@color/purple_700</item>
<item name="colorOnPrimary">@color/white</item>
<!-- Secondary brand color. -->
<item name="colorSecondary">@color/teal_200</item>
<item name="colorSecondaryVariant">@color/teal_700</item>
<item name="colorOnSecondary">@color/black</item>
<!-- Status bar color. -->
<item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
<!-- Customize your theme here. -->
</style>
<style name="AppBottomSheetDialogTheme" parent="Theme.Design.Light.BottomSheetDialog">
<item name="bottomSheetStyle">@style/AppModalStyle</item>
</style>
<style name="BottomSheetDialogTheme" parent="Theme.Design.Light.BottomSheetDialog">
<item name="bottomSheetStyle">@style/BottomSheetStyle</item>
</style>
<style name="BottomSheetStyle" parent="Widget.Design.BottomSheet.Modal">
<item name="android:background">@android:color/transparent</item>
</style>
<style name="AppModalStyle" parent="Widget.Design.BottomSheet.Modal">
<item name="android:background">@drawable/rounded_drawable</item>
</style>
<style name="LoginTextInputLayoutStyle" parent="Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense">
<item name="boxStrokeColor">#296D98</item>
<item name="boxStrokeWidth">1dp</item>
</style>
</resources>
第 7 步:为我们的按钮和自定义进度条背景创建自定义背景
导航到应用程序> res >可绘制>右键单击它>新建可绘制资源文件并将其命名为按钮 _ 后退并向其添加以下代码。代码中添加了注释，以便详细了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<!--for specifying corner radius-->
<corners android:radius="20dp" />
<!-- for specifying solid color-->
<solid android:color="@color/black_shade_1" />
</shape>
导航到应用程序> res >可绘制>右键单击它>新建可绘制资源文件并将其命名为 progress_back 并添加以下代码。代码中添加了注释，以便详细了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<rotate
xmlns:android="http://schemas.android.com/apk/res/android"
android:fromDegrees="0"
android:pivotX="50%"
android:pivotY="50%"
android:toDegrees="360">
<!--shape tag is used to
build a shape in XML-->
<shape
android:innerRadiusRatio="3"
android:shape="ring"
android:thicknessRatio="8"
android:useLevel="false">
<!--set the size of the shape-->
<size
android:width="76dip"
android:height="76dip" />
<!--set the color gradients
of the shape-->
<gradient
android:angle="0"
android:endColor="#00ffffff"
android:startColor="@color/purple_200"
android:type="sweep"
android:useLevel="false" />
</shape>
</rotate>
第 8 步:使用 activity_register.xml 文件
导航至应用程序>RES>activity _ register . XML，并添加以下代码。代码中添加了注释，以便更详细地了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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"
android:background="@color/black_shade_1"
tools:context=".RegisterActivity">
<!--edit text for user name-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILUserName"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="140dp"
android:layout_marginEnd="20dp"
android:hint="Enter User Name"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtUserName"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textEmailAddress"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for user password-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILPassword"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idTILUserName"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="20dp"
android:hint="Enter Your Password"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtPassword"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textPassword"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for confirmation of user password-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILConfirmPassword"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idTILPassword"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="20dp"
android:hint="Confirm Your Password"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtConfirmPassword"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textPassword"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--button for creating user account.-->
<Button
android:id="@+id/idBtnRegister"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idTILConfirmPassword"
android:layout_marginStart="25dp"
android:layout_marginTop="40dp"
android:layout_marginEnd="25dp"
android:background="@drawable/button_back"
android:text="Register"
android:textAllCaps="false" />
<!--text view for displaying a text on
clicking we will open a login page-->
<TextView
android:id="@+id/idTVLoginUser"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idBtnRegister"
android:layout_marginTop="40dp"
android:gravity="center"
android:padding="10dp"
android:text="Already a User ? Login Here"
android:textAlignment="center"
android:textAllCaps="false"
android:textColor="@color/white"
android:textSize="18sp" />
<!--progress bar as a loading indicator-->
<ProgressBar
android:id="@+id/idPBLoading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:indeterminate="true"
android:indeterminateDrawable="@drawable/progress_back"
android:visibility="gone" />
</RelativeLayout>
第九步:使用 RegisterActivity.java 文件
导航到应用程序> java >你的应用程序的包名>RegisterActivity.java文件，并添加下面的代码。代码中添加了注释，以便更详细地了解。
Java 语言(一种计算机语言，尤用于创建网站)
package com.gtappdevelopers.firebasecrudapp;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.textfield.TextInputEditText;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
public class RegisterActivity extends AppCompatActivity {
// cretaing variables for edit text and textview,
// firebase auth, button and progress bar.
private TextInputEditText userNameEdt, passwordEdt, confirmPwdEdt;
private TextView loginTV;
private Button registerBtn;
private FirebaseAuth mAuth;
private ProgressBar loadingPB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
// initializing all our variables.
userNameEdt = findViewById(R.id.idEdtUserName);
passwordEdt = findViewById(R.id.idEdtPassword);
loadingPB = findViewById(R.id.idPBLoading);
confirmPwdEdt = findViewById(R.id.idEdtConfirmPassword);
loginTV = findViewById(R.id.idTVLoginUser);
registerBtn = findViewById(R.id.idBtnRegister);
mAuth = FirebaseAuth.getInstance();
// adding on click for login tv.
loginTV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// opening a login activity on clicking login text.
Intent i = new Intent(RegisterActivity.this, LoginActivity.class);
startActivity(i);
}
});
// adding click listener for register button.
registerBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// hiding our progress bar.
loadingPB.setVisibility(View.VISIBLE);
// getting data fro =m our edit text.
String userName = userNameEdt.getText().toString();
String pwd = passwordEdt.getText().toString();
String cnfPwd = confirmPwdEdt.getText().toString();
// checking if the password and confirm password is equal or not.
if (!pwd.equals(cnfPwd)) {
Toast.makeText(RegisterActivity.this, "Please check both having same password..", Toast.LENGTH_SHORT).show();
} else if (TextUtils.isEmpty(userName) && TextUtils.isEmpty(pwd) && TextUtils.isEmpty(cnfPwd)) {
// checking if the text fields are empty or not.
Toast.makeText(RegisterActivity.this, "Please enter your credentials..", Toast.LENGTH_SHORT).show();
} else {
// on below line we are creating a new user by passing email and password.
mAuth.createUserWithEmailAndPassword(userName, pwd).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
// on below line we are checking if the task is success or not.
if (task.isSuccessful()) {
// in on success method we are hiding our progress bar and opening a login activity.
loadingPB.setVisibility(View.GONE);
Toast.makeText(RegisterActivity.this, "User Registered..", Toast.LENGTH_SHORT).show();
Intent i = new Intent(RegisterActivity.this, LoginActivity.class);
startActivity(i);
finish();
} else {
// in else condition we are displaying a failure toast message.
loadingPB.setVisibility(View.GONE);
Toast.makeText(RegisterActivity.this, "Fail to register user..", Toast.LENGTH_SHORT).show();
}
}
});
}
}
});
}
}
第十步:使用 activity_login.xml 文件
导航至应用程序>RES>activity _ log in . XML，并添加以下代码。代码中添加了注释，以便更详细地了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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"
android:background="@color/black_shade_1"
tools:context=".LoginActivity">
<!--edit text for user name-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILUserName"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="140dp"
android:layout_marginEnd="20dp"
android:hint="Enter User Name"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtUserName"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textEmailAddress"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for password-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILPassword"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idTILUserName"
android:layout_marginStart="20dp"
android:layout_marginTop="40dp"
android:layout_marginEnd="20dp"
android:hint="Enter your Password"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtPassword"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textPassword"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--button for login-->
<Button
android:id="@+id/idBtnLogin"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idTILPassword"
android:layout_marginStart="25dp"
android:layout_marginTop="40dp"
android:layout_marginEnd="25dp"
android:background="@drawable/button_back"
android:text="Login"
android:textAllCaps="false"
/>
<!--text view for creating a new account-->
<TextView
android:id="@+id/idTVNewUser"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idBtnLogin"
android:layout_marginTop="40dp"
android:gravity="center"
android:padding="10dp"
android:text="New User ? Register Here"
android:textAlignment="center"
android:textAllCaps="false"
android:textColor="@color/white"
android:textSize="18sp" />
<!--progress-bar for loading indicator-->
<ProgressBar
android:id="@+id/idPBLoading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/idTVNewUser"
android:layout_centerHorizontal="true"
android:layout_marginTop="10dp"
android:indeterminate="true"
android:indeterminateDrawable="@drawable/progress_back"
android:visibility="gone" />
</RelativeLayout>
第 11 步:使用 LoginActivity.java 文件
导航到应用程序> java >你的应用程序的包名>LoginActivity.java 文件并添加下面的代码。代码中添加了注释，以便更详细地了解。
Java 语言(一种计算机语言，尤用于创建网站)
package com.gtappdevelopers.firebasecrudapp;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.textfield.TextInputEditText;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
public class LoginActivity extends AppCompatActivity {
// creating variable for edit text, textview,
// button, progress bar and firebase auth.
private TextInputEditText userNameEdt, passwordEdt;
private Button loginBtn;
private TextView newUserTV;
private FirebaseAuth mAuth;
private ProgressBar loadingPB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
// initializing all our variables.
userNameEdt = findViewById(R.id.idEdtUserName);
passwordEdt = findViewById(R.id.idEdtPassword);
loginBtn = findViewById(R.id.idBtnLogin);
newUserTV = findViewById(R.id.idTVNewUser);
mAuth = FirebaseAuth.getInstance();
loadingPB = findViewById(R.id.idPBLoading);
// adding click listener for our new user tv.
newUserTV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// on below line opening a login activity.
Intent i = new Intent(LoginActivity.this, RegisterActivity.class);
startActivity(i);
}
});
// adding on click listener for our login button.
loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// hiding our progress bar.
loadingPB.setVisibility(View.VISIBLE);
// getting data from our edit text on below line.
String email = userNameEdt.getText().toString();
String password = passwordEdt.getText().toString();
// on below line validating the text input.
if (TextUtils.isEmpty(email) && TextUtils.isEmpty(password)) {
Toast.makeText(LoginActivity.this, "Please enter your credentials..", Toast.LENGTH_SHORT).show();
return;
}
// on below line we are calling a sign in method and passing email and password to it.
mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
// on below line we are checking if the task is succes or not.
if (task.isSuccessful()) {
// on below line we are hiding our progress bar.
loadingPB.setVisibility(View.GONE);
Toast.makeText(LoginActivity.this, "Login Successful..", Toast.LENGTH_SHORT).show();
// on below line we are opening our mainactivity.
Intent i = new Intent(LoginActivity.this, MainActivity.class);
startActivity(i);
finish();
} else {
// hiding our progress bar and displaying a toast message.
loadingPB.setVisibility(View.GONE);
Toast.makeText(LoginActivity.this, "Please enter valid user credentials..", Toast.LENGTH_SHORT).show();
}
}
});
}
});
}
@Override
protected void onStart() {
super.onStart();
// in on start method checking if
// the user is already sign in.
FirebaseUser user = mAuth.getCurrentUser();
if (user != null) {
// if the user is not null then we are
// opening a main activity on below line.
Intent i = new Intent(LoginActivity.this, MainActivity.class);
startActivity(i);
this.finish();
}
}
}
第 12 步:为我们的数据创建一个模态类，显示在我们的回收视图中
导航到应用程序> java >你的应用程序的包名>右键点击它>新建> Java 类并将其命名为 CourseRVModal 并添加下面的代码。代码中添加了注释，以便更详细地了解。
Java 语言(一种计算机语言，尤用于创建网站)
package com.gtappdevelopers.firebasecrudapp;
import android.os.Parcel;
import android.os.Parcelable;
public class CourseRVModal implements Parcelable {
// creating variables for our different fields.
private String courseName;
private String courseDescription;
private String coursePrice;
private String bestSuitedFor;
private String courseImg;
private String courseLink;
private String courseId;
public String getCourseId() {
return courseId;
}
public void setCourseId(String courseId) {
this.courseId = courseId;
}
// creating an empty constructor.
public CourseRVModal() {
}
protected CourseRVModal(Parcel in) {
courseName = in.readString();
courseId = in.readString();
courseDescription = in.readString();
coursePrice = in.readString();
bestSuitedFor = in.readString();
courseImg = in.readString();
courseLink = in.readString();
}
public static final Creator<CourseRVModal> CREATOR = new Creator<CourseRVModal>() {
@Override
public CourseRVModal createFromParcel(Parcel in) {
return new CourseRVModal(in);
}
@Override
public CourseRVModal[] newArray(int size) {
return new CourseRVModal[size];
}
};
// creating getter and setter methods.
public String getCourseName() {
return courseName;
}
public void setCourseName(String courseName) {
this.courseName = courseName;
}
public String getCourseDescription() {
return courseDescription;
}
public void setCourseDescription(String courseDescription) {
this.courseDescription = courseDescription;
}
public String getCoursePrice() {
return coursePrice;
}
public void setCoursePrice(String coursePrice) {
this.coursePrice = coursePrice;
}
public String getBestSuitedFor() {
return bestSuitedFor;
}
public void setBestSuitedFor(String bestSuitedFor) {
this.bestSuitedFor = bestSuitedFor;
}
public String getCourseImg() {
return courseImg;
}
public void setCourseImg(String courseImg) {
this.courseImg = courseImg;
}
public String getCourseLink() {
return courseLink;
}
public void setCourseLink(String courseLink) {
this.courseLink = courseLink;
}
public CourseRVModal(String courseId, String courseName, String courseDescription, String coursePrice, String bestSuitedFor, String courseImg, String courseLink) {
this.courseName = courseName;
this.courseId = courseId;
this.courseDescription = courseDescription;
this.coursePrice = coursePrice;
this.bestSuitedFor = bestSuitedFor;
this.courseImg = courseImg;
this.courseLink = courseLink;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(courseName);
dest.writeString(courseId);
dest.writeString(courseDescription);
dest.writeString(coursePrice);
dest.writeString(bestSuitedFor);
dest.writeString(courseImg);
dest.writeString(courseLink);
}
}
在数据库中创建操作
第 13 步:使用 activity_add_course.xml 文件
导航至应用程序> res >布局> activity_add_course.xml 并添加以下代码。代码中添加了注释，以便更详细地了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
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"
android:background="@color/black_shade_1"
tools:context=".AddCourseActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<!--edit text for course name-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCourseName"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Name"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtCourseName"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textImeMultiLine|textMultiLine"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for course price-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCoursePrice"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Price"
android:padding="5dp"
android:textColorHint="@color/white"
app:boxStrokeColor="@color/purple_200"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtCoursePrice"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="phone"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp"
app:boxStrokeColor="@color/purple_200" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for course suited for-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCourseSuitedFor"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Suited For"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtSuitedFor"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textImeMultiLine|textMultiLine"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for course image link-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCourseImageLink"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Image Link"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtCourseImageLink"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textImeMultiLine|textMultiLine"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for course link-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCourseLink"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Link"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtCourseLink"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textImeMultiLine|textMultiLine"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--edit text for course description-->
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/idTILCourseDescription"
style="@style/LoginTextInputLayoutStyle"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:hint="Enter Course Description"
android:padding="5dp"
android:textColorHint="@color/white"
app:hintTextColor="@color/white">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/idEdtCourseDescription"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:importantForAutofill="no"
android:inputType="textImeMultiLine|textMultiLine"
android:textColor="@color/white"
android:textColorHint="@color/white"
android:textSize="14sp" />
</com.google.android.material.textfield.TextInputLayout>
<!--button for adding a new course-->
<Button
android:id="@+id/idBtnAddCourse"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="10dp"
android:layout_marginBottom="10dp"
android:background="@drawable/button_back"
android:text="Add Your Course"
android:textAllCaps="false" />
</LinearLayout>
<!--progress bar for loading indicator-->
<ProgressBar
android:id="@+id/idPBLoading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_gravity="center"
android:indeterminate="true"
android:indeterminateDrawable="@drawable/progress_back"
android:visibility="gone" />
</RelativeLayout>
</ScrollView>
步骤 14:使用 AddCourseActivity.java 文件
导航到应用程序> java >你的应用程序的包名>AddCourseActivity.java文件，并添加下面的代码。代码中添加了注释，以便更详细地了解。
Java 语言(一种计算机语言，尤用于创建网站)
package com.gtappdevelopers.firebasecrudapp;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.material.textfield.TextInputEditText;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
public class AddCourseActivity extends AppCompatActivity {
// creating variables for our button, edit text,
// firebase database, database reference, progress bar.
private Button addCourseBtn;
private TextInputEditText courseNameEdt, courseDescEdt, coursePriceEdt, bestSuitedEdt, courseImgEdt, courseLinkEdt;
FirebaseDatabase firebaseDatabase;
DatabaseReference databaseReference;
private ProgressBar loadingPB;
private String courseID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_course);
// initializing all our variables.
addCourseBtn = findViewById(R.id.idBtnAddCourse);
courseNameEdt = findViewById(R.id.idEdtCourseName);
courseDescEdt = findViewById(R.id.idEdtCourseDescription);
coursePriceEdt = findViewById(R.id.idEdtCoursePrice);
bestSuitedEdt = findViewById(R.id.idEdtSuitedFor);
courseImgEdt = findViewById(R.id.idEdtCourseImageLink);
courseLinkEdt = findViewById(R.id.idEdtCourseLink);
loadingPB = findViewById(R.id.idPBLoading);
firebaseDatabase = FirebaseDatabase.getInstance();
// on below line creating our database reference.
databaseReference = firebaseDatabase.getReference("Courses");
// adding click listener for our add course button.
addCourseBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
loadingPB.setVisibility(View.VISIBLE);
// getting data from our edit text.
String courseName = courseNameEdt.getText().toString();
String courseDesc = courseDescEdt.getText().toString();
String coursePrice = coursePriceEdt.getText().toString();
String bestSuited = bestSuitedEdt.getText().toString();
String courseImg = courseImgEdt.getText().toString();
String courseLink = courseLinkEdt.getText().toString();
courseID = courseName;
// on below line we are passing all data to our modal class.
CourseRVModal courseRVModal = new CourseRVModal(courseID, courseName, courseDesc, coursePrice, bestSuited, courseImg, courseLink);
// on below line we are calling a add value event
// to pass data to firebase database.
databaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
// on below line we are setting data in our firebase database.
databaseReference.child(courseID).setValue(courseRVModal);
// displaying a toast message.
Toast.makeText(AddCourseActivity.this, "Course Added..", Toast.LENGTH_SHORT).show();
// starting a main activity.
startActivity(new Intent(AddCourseActivity.this, MainActivity.class));
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
// displaying a failure message on below line.
Toast.makeText(AddCourseActivity.this, "Fail to add Course..", Toast.LENGTH_SHORT).show();
}
});
}
});
}
}
从数据库读取操作
第 15 步:在我们的回收视图中为每个课程创建一个项目。
导航至 app > res >右键单击>新建布局资源文件并将其命名为 course_rv_item 并添加以下代码。代码中添加了注释，以便更详细地了解。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="5dp"
app:cardCornerRadius="4dp"
app:cardElevation="3dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/black_shade_1">
<!--image view for our course-->
<ImageView
android:id="@+id/idIVCourse"
android:layout_width="match_parent"
android:layout_height="200dp"
android:scaleType="centerCrop" />
<!--text view for course name-->
<TextView
android:id="@+id/idTVCOurseName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/idIVCourse"
android:layout_margin="3dp"
android:layout_toStartOf="@id/idTVCousePrice"
android:layout_toLeftOf="@id/idTVCousePrice"
android:padding="4dp"
android:text="Course Name"
android:textColor="@color/white"
android:textSize="15sp"
android:textStyle="bold" />
<!--text view for course price-->
<TextView
android:id="@+id/idTVCousePrice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/idIVCourse"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_margin="3dp"
android:gravity="center"
android:padding="4dp"
android:text="Price"
android:textColor="@color/white"
android:textSize="15sp"
android:textStyle="bold" />
</RelativeLayout>
</androidx.cardview.widget.CardView>
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