Android SQLite 數據庫示例 · JavaTutorialNetwork 中文系列教程

# Android SQLite 數據庫示例 > 原文： [https://javatutorial.net/android-sqlite-database-example](https://javatutorial.net/android-sqlite-database-example) [上一教程(https://javatutorial.net/android-sqlite-database-introduction)對 Android 中的 SQLite 數據庫進行了簡介。本教程以示例說明了所有 CRUD（創建，檢索，更新，刪除）功能。 ## 示例背景讓我們開始使用 SQLite 數據庫。本示例全部有關注冊和登錄過程以及將用戶憑據存儲到數據庫中的逐步說明。當用戶單擊“注冊”按鈕時，將出現一個新活動，并且用戶填寫該表單，該表單具有四個值，分別是名字，姓氏，電子郵件 ID 和密碼。當用戶單擊“確定”按鈕時，這些值將保存到數據庫中。下圖顯示了數據庫中的注冊表的外觀 ![login table](https://img.kancloud.cn/bf/d3/bfd3288878673279868a5d038be36850_300x191.jpg) 登錄表 ## 第 1 步：活動布局讓我們開始創建用于注冊和登錄的 xml 布局。如上所述，注冊有四個字段和一個確定按鈕。用戶單擊“確定”按鈕時，將顯示一個對話框，因為已保存值，然后將開始登錄活動。這是`activity_main.xml`的代碼 ```java <?xml version="1.0" encoding="utf-8"?> <RelativeLayout android:layout_width="368dp" android:layout_height="495dp" xmlns:tools="http://schemas.android.com/tools" tools:layout_editor_absoluteX="8dp" tools:layout_editor_absoluteY="8dp" xmlns:android="http://schemas.android.com/apk/res/android"> <TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:layout_marginTop="104dp" android:text="Sign In" android:textColor="@android:color/holo_red_dark" android:textSize="25sp" /> <EditText android:id="@+id/Email" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/textView2" android:layout_centerHorizontal="true" android:layout_marginTop="26dp" android:ems="10" android:inputType="textPersonName" android:text="Email ID" /> <EditText android:id="@+id/Password" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignEnd="@+id/Email" android:layout_alignRight="@+id/Email" android:layout_centerVertical="true" android:ems="10" android:inputType="textPassword" android:text="password" /> <Button android:id="@+id/buttonSignIn" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/Password" android:layout_alignStart="@+id/Password" android:layout_below="@+id/Password" android:layout_marginTop="52dp" android:backgroundTint="@color/colorAccent" android:onClick="SignIN" android:text="Sign In" /> <Button android:id="@+id/buttonSignUp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignEnd="@+id/Password" android:layout_alignRight="@+id/Password" android:layout_alignTop="@+id/buttonSignIn" android:backgroundTint="@color/colorAccent" android:onClick="SignUP" android:text="Sign Up" /> </RelativeLayout> ``` 現在為`activity_sign_up.xml`創建另一個布局。登錄有兩個字段和兩個按鈕，分別是“登錄”和“登錄”。如果您已經有一個帳戶，請輸入 ID 和密碼并登錄。如果沒有，請單擊“注冊”按鈕并為您創建帳戶。 ```java <?xml version="1.0" encoding="utf-8"?> <RelativeLayout android:layout_width="368dp" android:layout_height="495dp" xmlns:tools="http://schemas.android.com/tools" tools:layout_editor_absoluteX="8dp" tools:layout_editor_absoluteY="8dp" xmlns:android="http://schemas.android.com/apk/res/android"> <TextView android:id="@+id/tSignUP" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Sign Up" android:textColor="@android:color/holo_red_dark" android:textSize="25sp" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:layout_marginTop="22dp" /> <EditText android:id="@+id/tFirstName" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/tSignUP" android:layout_centerHorizontal="true" android:layout_marginTop="26dp" android:ems="10" android:inputType="textPersonName" android:text="First Name" /> <EditText android:id="@+id/tPassword" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="10" android:inputType="textPassword" android:text="password" android:layout_below="@+id/tEmail" android:layout_alignLeft="@+id/tEmail" android:layout_alignStart="@+id/tEmail" android:layout_marginTop="23dp" /> <EditText android:id="@+id/tLastName" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/tFirstName" android:layout_alignStart="@+id/tFirstName" android:layout_below="@+id/tFirstName" android:layout_marginTop="14dp" android:ems="10" android:inputType="textPersonName" android:text="Last Name" /> <EditText android:id="@+id/tEmail" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignEnd="@+id/tLastName" android:layout_alignRight="@+id/tLastName" android:layout_below="@+id/tLastName" android:layout_marginTop="25dp" android:ems="10" android:inputType="textPersonName" android:text="Email ID" /> <Button android:id="@+id/buttonOK" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignEnd="@+id/tPassword" android:layout_alignRight="@+id/tPassword" android:layout_below="@+id/tPassword" android:layout_marginTop="47dp" android:background="@color/colorAccent" android:onClick="OK" android:text="OK" /> </RelativeLayout> ``` ## 步驟 2：創建數據庫助手類此類在磁盤上創建數據庫。 ```java package com.example.admin.androiddatabaseexample; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DataBaseHelper extends SQLiteOpenHelper { public DataBaseHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); } // Called when no database exists in disk and the helper class needs // to create a new one. @Override public void onCreate(SQLiteDatabase _db) { try { _db.execSQL(LoginDatabaseAdapter.DATABASE_CREATE); }catch(Exception er){ Log.e("Error","exceptioin"); } } // Called when there is a database version mismatch meaning that the version // of the database on disk needs to be upgraded to the current version. @Override public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion) { // Log the version upgrade. Log.w("TaskDBAdapter", "Upgrading from version " +_oldVersion + " to " +_newVersion + ", which will destroy all old data"); // Upgrade the existing database to conform to the new version. Multiple // previous versions can be handled by comparing _oldVersion and _newVersion // values. // The simplest case is to drop the old table and create a new one. _db.execSQL("DROP TABLE IF EXISTS " + "LOGIN"); // Create a new one. onCreate(_db); } } ``` ## 步驟 3：創建登錄數據庫類登錄數據庫是一類，您在其中實現所有數據庫編碼。首先使用四個字段創建用于登錄的表，然后實現所有其他方法。 ```java package com.example.admin.androiddatabaseexample; import android.app.AlertDialog; import android.content.ContentValues; import android.content.Context; import android.content.DialogInterface; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.util.Log; import android.widget.Toast; import java.util.ArrayList; import java.util.List; public class LoginDatabaseAdapter { static final String DATABASE_NAME = "database.db"; String ok="OK"; static final int DATABASE_VERSION = 1; public static String getPassword=""; public static final int NAME_COLUMN = 1; // TODO: Create public field for each column in your table. // SQL Statement to create a new database. static final String DATABASE_CREATE = "create table LOGIN( ID integer primary key autoincrement,FIRSTNAME text,LASTNAME text,USERNAME text,PASSWORD text); "; // Variable to hold the database instance public static SQLiteDatabase db; // Context of the application using the database. private final Context context; // Database open/upgrade helper private static DataBaseHelper dbHelper; public LoginDatabaseAdapter(Context _context) { context = _context; dbHelper = new DataBaseHelper(context, DATABASE_NAME, null, DATABASE_VERSION); } // Method to openthe Database public LoginDatabaseAdapter open() throws SQLException { db = dbHelper.getWritableDatabase(); return this; } // Method to close the Database public void close() { db.close(); } // method returns an Instance of the Database public SQLiteDatabase getDatabaseInstance() { return db; } // method to insert a record in Table public String insertEntry(String firstName,String lastName,String Id,String password) { try { ContentValues newValues = new ContentValues(); // Assign values for each column. newValues.put("FIRSTNAME", firstName); newValues.put("LASTNAME", lastName); newValues.put("USERNAME", Id); newValues.put("PASSWORD", password); // Insert the row into your table db = dbHelper.getWritableDatabase(); long result=db.insert("LOGIN", null, newValues); System.out.print(result); Toast.makeText(context, "User Info Saved", Toast.LENGTH_LONG).show(); }catch(Exception ex) { System.out.println("Exceptions " +ex); Log.e("Note", "One row entered"); } return ok; } // method to delete a Record of UserName public int deleteEntry(String UserName) { String where="USERNAME=?"; int numberOFEntriesDeleted= db.delete("LOGIN", where, new String[]{UserName}) ; Toast.makeText(context, "Number fo Entry Deleted Successfully : "+numberOFEntriesDeleted, Toast.LENGTH_LONG).show(); return numberOFEntriesDeleted; } // method to get the password of userName public String getSinlgeEntry(String userName) { db=dbHelper.getReadableDatabase(); Cursor cursor=db.query("LOGIN", null, "USERNAME=?", new String[]{userName}, null, null, null); if(cursor.getCount()<1) // UserName Not Exist return "NOT EXIST"; cursor.moveToFirst(); getPassword= cursor.getString(cursor.getColumnIndex("PASSWORD")); return getPassword; } // Method to Update an Existing public void updateEntry(String userName,String password) { // create object of ContentValues ContentValues updatedValues = new ContentValues(); // Assign values for each Column. updatedValues.put("USERNAME", userName); updatedValues.put("PASSWORD", password); String where="USERNAME = ?"; db.update("LOGIN",updatedValues, where, new String[]{userName}); } } ``` ## 步驟 4：`MainActivity.java` 在該類中，您可以從登錄活動中獲取 ID 和密碼，并在點擊監聽器上實現登錄和注冊按鈕。 ```java package com.example.admin.androiddatabaseexample; import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.EditText; public class MainActivity extends AppCompatActivity { private EditText etUserEmail; private EditText etPassword; public String username; private String password; String storedPassword; Context context=this; LoginDatabaseAdapter loginDataBaseAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // create the instance of Databse loginDataBaseAdapter=new LoginDatabaseAdapter(getApplicationContext()); etUserEmail = (EditText) findViewById(R.id.Email); etPassword = (EditText) findViewById(R.id.Password); } public void SignIN(View view) { try { loginDataBaseAdapter = loginDataBaseAdapter.open(); username = etUserEmail.getText().toString(); password = etPassword.getText().toString(); if (username.equals("") || password.equals("")) { AlertDialog alertDialog = new AlertDialog.Builder(this).create(); alertDialog.setTitle("ALERT!"); alertDialog.setMessage("Fill All Fields"); alertDialog.setButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { } }); alertDialog.show(); } // fetch the Password form database for respective user name if (!username.equals("")) { storedPassword = loginDataBaseAdapter.getSinlgeEntry(username); // check if the Stored password matches with Password entered by user if (password.equals(storedPassword)) { Intent intent1 = new Intent(MainActivity.this, DisplayInfoActivity.class); startActivity(intent1); // finish(); } else { AlertDialog alertDialog = new AlertDialog.Builder(this).create(); alertDialog.setTitle("ALERT!"); alertDialog.setMessage("Incorrect Username OR Password"); alertDialog.setButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { } }); alertDialog.show(); } } } catch (Exception ex) { Log.e("Error", "error login"); } } public void SignUP(View view) { Intent intent = new Intent(MainActivity.this, SignUp.class); startActivity(intent); } @Override protected void onDestroy() { // TODO Auto-generated method stub super.onDestroy(); // Close The Database loginDataBaseAdapter.close(); } } ``` ## 步驟 5：`SignUp.java` 當用戶在注冊活動中單擊“確定”按鈕時，將出現一個對話框，指出值已添加到數據庫的登錄表中。 ```java package com.example.admin.androiddatabaseexample; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.view.View; import android.widget.EditText; public class SignUp extends AppCompatActivity { Context context=this; private EditText et_first_name; private EditText et_last_name; private EditText et_ID; private EditText et_password; private String firstName; private String lastName; private String userName; private String password; String receieveOk; LoginDatabaseAdapter loginDataBaseAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_sign_up); // get Instance of Database Adapter loginDataBaseAdapter=new LoginDatabaseAdapter(getApplicationContext()); loginDataBaseAdapter=loginDataBaseAdapter.open(); et_first_name = (EditText) findViewById(R.id.tFirstName); et_last_name = (EditText) findViewById(R.id.tLastName); et_ID = (EditText) findViewById(R.id.tEmail); et_password = (EditText) findViewById(R.id.tPassword); } public void OK(View view) { firstName = et_first_name.getText().toString(); lastName = et_last_name.getText().toString(); userName = et_ID.getText().toString(); password = et_ID.getText().toString(); if((firstName.equals(""))||(lastName.equals(""))||(userName.equals(""))||(password.equals(""))) { //Display Message AlertDialog alertDialog = new AlertDialog.Builder(this).create(); alertDialog.setTitle("ALERT!"); alertDialog.setMessage("All fields must be filled"); alertDialog.setButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { } }); alertDialog.show(); } else { // Save the Data in Database receieveOk=loginDataBaseAdapter.insertEntry(firstName,lastName,userName, password); AlertDialog alertDialog = new AlertDialog.Builder(this).create(); alertDialog.setTitle("SUCCESSFUL!"); alertDialog.setMessage("SIGN IN NOW " + receieveOk); alertDialog.setButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { Intent intent = new Intent(SignUp.this, MainActivity.class); startActivity(intent); } }); alertDialog.show(); finish(); } } @Override protected void onDestroy() { // TODO Auto-generated method stub super.onDestroy(); loginDataBaseAdapter.close(); } } ``` 現在運行您的應用程序并進行測試。這是正在運行的應用程序的屏幕截圖 ![sign in](https://img.kancloud.cn/71/bc/71bcacfeeae558e8e0971fb16b1b5675_367x685.jpg) 登入 ![wrong id or password](https://img.kancloud.cn/d9/61/d961596dee2e0407e6535593845de556_371x650.jpg) 錯誤的 ID 或密碼 ![sign up](https://img.kancloud.cn/3d/0e/3d0e7f3f6fe780c4a754dba901515b0f_369x649.jpg) 注冊您可以從[鏈接](https://github.com/JavaTutorialNetwork/Tutorials/blob/master/AndroidDatabaseExample.rar)下載此代碼。