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Android Studio入门实战--实现数据库增删查改 备忘录实例_androidstudio询百度云数据库数据

作者：Cpp五条 | 2024-04-23 18:05:14

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androidstudio询百度云数据库数据

目录

要求目的：

效果图：

Android studio sql 数据库查看工具

SQLiteStudio

MainActivity内容：

EditText带icon的布局文件：

定义Myhepler.java  ——用户部分——

定义注册登录事件

注册按钮绑定插入用户记录事件：

登录按钮绑定匹配数据库用户密码是否正确并且传值跳转Content页面事件：

 ContentActivity：

布局xml文件：

定义Myhelper.java——备忘录数据增删查改——

长按删除数据记录：

短按编辑：

添加备忘录按钮：

onResume()函数实时更新回调函数：

全部代码：

要求目的：

              1.  数据库需要存储用户信息、及备忘录信息，

              2.  每个用户都有各自的备忘录信息，信息互不干扰

              3.  根据按钮 完成数据库 增删查改，实时更新信息

效果图：

                

Android studio sql 数据库查看工具

SQLiteStudio

下载链接

 官网           SQLiteStudioicon-default.png?t=N7T8https://sqlitestudio.pl/

在本地android studio 上 查询数据库并且复制到桌面用sqlitestudio 工具查看

结果如下：

MainActivity内容：

EditText带icon的布局文件：

                xml布局文件

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:background="@drawable/img"
  8.     tools:context=".MainActivity">
  9.  
  10.     <ImageView
  11.         android:id="@+id/imageView"
  12.         android:layout_width="122dp"
  13.         android:layout_height="109dp"
  14.         android:layout_marginStart="152dp"
  15.         android:layout_marginBottom="44dp"
  16.         android:src="@drawable/userimg"
  17.         app:layout_constraintBottom_toTopOf="@+id/loginView"
  18.         app:layout_constraintStart_toStartOf="parent" />
  19.  
  20.     <EditText
  21.         android:id="@+id/loginView"
  22.         android:layout_width="235dp"
  23.         android:layout_height="51dp"
  24.         android:layout_marginStart="108dp"
  25.         android:layout_marginTop="232dp"
  26.         android:background="@android:drawable/editbox_background"
  27.         android:hint=" Enter your name"
  28.         app:layout_constraintStart_toStartOf="parent"
  29.         app:layout_constraintTop_toTopOf="parent" />
  30.  
  31.     <EditText
  32.         android:id="@+id/passwordView"
  33.         android:layout_width="240dp"
  34.         android:layout_height="50dp"
  35.         android:layout_marginStart="104dp"
  36.         android:layout_marginTop="36dp"
  37.         android:background="@android:drawable/editbox_background"
  38.         android:hint=" Enter your password"
  39.         app:layout_constraintStart_toStartOf="parent"
  40.         app:layout_constraintTop_toBottomOf="@+id/loginView" />
  41.  
  42.     <Button
  43.         android:id="@+id/loginbutton"
  44.         android:layout_width="wrap_content"
  45.         android:layout_height="wrap_content"
  46.         android:layout_marginStart="84dp"
  47.         android:layout_marginTop="144dp"
  48.         android:text="登录"
  49.         app:layout_constraintStart_toStartOf="parent"
  50.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  51.  
  52.     <Button
  53.         android:id="@+id/registerbutton"
  54.         android:layout_width="wrap_content"
  55.         android:layout_height="wrap_content"
  56.         android:layout_marginTop="144dp"
  57.         android:layout_marginEnd="40dp"
  58.         android:text="注册"
  59.         app:layout_constraintEnd_toEndOf="parent"
  60.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  61.  
  62.     <CheckBox
  63.         android:id="@+id/checkBox"
  64.         android:layout_width="wrap_content"
  65.         android:layout_height="wrap_content"
  66.         android:layout_marginTop="68dp"
  67.         android:layout_marginEnd="36dp"
  68.         android:text="记住密码"
  69.         android:textAppearance="@style/TextAppearance.AppCompat.Medium"
  70.         app:layout_constraintEnd_toEndOf="parent"
  71.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  72.  
  73. </androidx.constraintlayout.widget.ConstraintLayout>

        icon 文件

  1. package com.example.myapplication;
  2.  
  3. import androidx.appcompat.app.AppCompatActivity;
  4.  
  5. import android.content.Intent;
  6. import android.content.SharedPreferences;
  7. import android.database.sqlite.SQLiteDatabase;
  8. import android.graphics.drawable.Drawable;
  9. import android.os.Bundle;
  10. import android.text.method.PasswordTransformationMethod;
  11. import android.widget.Button;
  12. import android.widget.CheckBox;
  13. import android.widget.EditText;
  14. import android.widget.Toast;
  15.  
  16. public class MainActivity extends AppCompatActivity   {
  17.  
  18.     private EditText editText;
  19.     private EditText editText1;
  20.     Drawable icon;
  21.     Drawable icon1;
  22.     private CheckBox checkBox;
  23.  
  24.     private  MyHelper myHelper;
  25.  
  26.  
  27.  
  28.     
  29.  
  30.     @Override
  31.     protected void onCreate(Bundle savedInstanceState) {
  32.         super.onCreate(savedInstanceState);
  33.         setContentView(R.layout.activity_main1);
  34.  
  35.         editText = findViewById(R.id.loginView);
  36.         editText1 = findViewById(R.id.passwordView);
  37.         editText1.setTransformationMethod(PasswordTransformationMethod.getInstance());//密码不可见
  38.  
  39.         icon = getResources().getDrawable(R.drawable.profile1);
  40.         icon1 = getResources().getDrawable(R.drawable.password);
  41.         icon.setBounds(0, 0, 80, 80);
  42.         editText.setCompoundDrawables(icon, null, null, null);
  43.         icon1.setBounds(0,0,80,80);
  44.         editText1.setCompoundDrawables(icon1, null, null, null);
  45.  
  46.        
  47.        
  48.  
  49.  
  50.  
  51.     }
  52. }

定义Myhepler.java  ——用户部分——

       建立用户表user_table及备忘录content_table

  1. package com.example.myapplication;
  2.  
  3. import android.annotation.SuppressLint;
  4. import android.content.Context;
  5. import android.database.Cursor;
  6. import android.database.sqlite.SQLiteDatabase;
  7. import android.database.sqlite.SQLiteOpenHelper;
  8. import android.widget.Toast;
  9.  
  10. import androidx.annotation.Nullable;
  11.  
  12. import java.util.ArrayList;
  13. import java.util.List;
  14.  
  15. public class MyHelper extends SQLiteOpenHelper {
  16.     private static final String dbname = "memo.db";
  17.     private static final  String UserTableName = "user_table";
  18.     private static  final  String ContentTableName = "content_table";
  19.     private List<String> memolist = new ArrayList<>();
  20.  
  21.     public MyHelper(@Nullable Context context) {
  22.         super(context,dbname, null, 2);
  23.     }
  24.  
  25.     @Override
  26.     public void onCreate(SQLiteDatabase sqLiteDatabase) {
  27.  
  28.         String sql_create1 = "CREATE TABLE IF NOT EXISTS "+ UserTableName +"("+"_id integer primary key autoincrement,username varchar not null,password varchar not null"+");";
  29.         sqLiteDatabase.execSQL(sql_create1);
  30.         String sql_create2 = "CREATE TABLE IF NOT EXISTS "+ ContentTableName +"("+"_id integer primary key autoincrement,username varchar not null,memotitle varchar not null"+");";
  31.         sqLiteDatabase.execSQL(sql_create2);
  32.  
  33.     }
  34. }

插入用户信息:

  1.  
  2.     //注册事件 插入user记录
  3.     protected  void insert_user(user user,SQLiteDatabase sqLiteDatabase){
  4.         sqLiteDatabase.execSQL("insert into user_table "
  5.                         + "(username,password)"
  6.                         + "values(?,?)"  ,
  7.                 new String[]{user.getUsername(), user.getPassword()}
  8.         );
  9.  
  10.     }

匹配用户及密码信息：

  1.  
  2.     //查询数据库 先按username 筛选记录 再与password字段匹配 ，如果不存在记录也是返回false
  3.     @SuppressLint("Range")
  4.     protected boolean queryuser(user user, SQLiteDatabase sqLiteDatabase){
  5.  
  6.         Cursor cursor = sqLiteDatabase.rawQuery("select * from user_table where username = ? and password = ?", new String[]{user.getUsername(), user.getPassword()});
  7.         if(cursor.moveToNext()) {
  8.  
  9.  
  10.             return true;
  11.  
  12.  
  13.         }
  14.         return false;
  15.     }

定义注册登录事件

注册按钮绑定插入用户记录事件：

  1.   myHelper = new MyHelper(MainActivity.this);
  2.         db = myHelper.getWritableDatabase();
  3.   register = findViewById(R.id.registerbutton);
  4. //注册事件
  5.   register.setOnClickListener(view -> {
  6.             user user = new user(editText.getText().toString(),editText1.getText().toString());
  7.             myHelper.insert_user(user,db);
  8.             Toast.makeText(MainActivity.this,"注册成功",Toast.LENGTH_LONG).show();
  9.         });

登录按钮绑定匹配数据库用户密码是否正确并且传值跳转Content页面事件：

  1. login.setOnClickListener(view -> {
  2.             user user = new user(editText.getText().toString(),editText1.getText().toString());
  3.  
  4.             if (myHelper.queryuser(user,db)){
  5.  
  6.                 Toast.makeText(MainActivity.this,"登陆成功",Toast.LENGTH_LONG).show();
  7.  
  8.                 Intent intent = new Intent(MainActivity.this,ContentActivity.class);
  9.                 intent.putExtra("username",editText.getText().toString());
  10.                 startActivity(intent);
  11.  
  12.             }else {
  13.                 Toast.makeText(MainActivity.this,"用户名或密码错误",Toast.LENGTH_LONG).show();
  14.             }
  15.         });

 ContentActivity：

布局xml文件：

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:orientation="vertical"
  8.     android:background="@drawable/background"
  9.     android:gravity="center"
  10.     tools:context=".ContentActivity">
  11.  
  12.     <TextView
  13.         android:id="@+id/textView"
  14.         android:layout_width="401dp"
  15.         android:layout_height="39dp"
  16.         android:text="备忘录"
  17.         android:textAlignment="center"
  18.         android:textAppearance="@style/TextAppearance.AppCompat.Large" />
  19.  
  20.     <ListView
  21.         android:id="@+id/listview"
  22.         android:layout_width="398dp"
  23.         android:layout_height="613dp" />
  24.  
  25.     <Button
  26.         android:id="@+id/button"
  27.         android:layout_width="wrap_content"
  28.         android:layout_height="65dp"
  29.         android:background="@android:drawable/ic_input_add"
  30.         android:backgroundTint="#E1D0D0"
  31.         app:rippleColor="@color/white" />
  32. </LinearLayout>

定义Myhelper.java——备忘录数据增删查改——

  1. //查询备忘录并且返回list
  2.     protected  List<String> queryMemo(String username,SQLiteDatabase db){
  3.         memolist.clear();
  4.  
  5.         Cursor cursor = db.rawQuery("select * from content_table where username = ? ", new String[]{username});
  6.  
  7.         while (cursor.moveToNext()){
  8.             memolist.add(cursor.getString(2));
  9.         }
  10.  
  11.  
  12.  
  13.  
  14.         return memolist;
  15.     }
  16.  
  17.     //插入备忘录
  18.     protected void insert_title(String username ,String title ,SQLiteDatabase db){
  19.         db.execSQL("insert into content_table "
  20.                         + "(username,memotitle)"
  21.                         + "values(?,?)"  ,
  22.                 new String[]{username, title}
  23.         );
  24.     }
  25.  
  26.  
  27.     //删除备忘录
  28.     public void delete_content(String username ,String title ,SQLiteDatabase db){
  29.         String sql = "delete from "+ ContentTableName +" where username like '"+username+"' and memotitle like '"+title
  30.                 +"';";
  31.         db.execSQL(sql);
  32.     }
  33.  
  34.     //更新备忘录
  35.     public void update_content(String username,String old_tit,String new_tit,SQLiteDatabase db){
  36.         String sql = "update "+ ContentTableName +" set memotitle = '"+new_tit+"'where username like '"
  37.                 +username+"' and memotitle like '"+old_tit+"';";
  38.         db.execSQL(sql);
  39.     }

长按删除数据记录：

  1.   //列表点击事件
  2.         //长按
  3.         listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
  4.             @Override
  5.             public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
  6.                 final String content = ((TextView) view).getText().toString();
  7.                 AlertDialog.Builder editDialog = new AlertDialog.Builder(ContentActivity.this);
  8.                 editDialog.setTitle(content);
  9.                 editDialog.setMessage("是否删除该备忘录");
  10.                 editDialog.setPositiveButton("确定", new DialogInterface.OnClickListener() {
  11.                     @Override
  12.                     public void onClick(DialogInterface dialogInterface, int i) {
  13.                         myHelper.delete_content(username, content, db);
  14.                         Toast.makeText(ContentActivity.this, "数据已删除", Toast.LENGTH_LONG).show();
  15.                         onResume();
  16.                     }
  17.                 });
  18.                 editDialog.show();
  19.                 return true;
  20.             }
  21.         });

短按编辑：

  1. //短按事件
  2.         listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
  3.             @Override
  4.             public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
  5.                 final String content = ((TextView) view).getText().toString();
  6.                 final EditText editText = new EditText(ContentActivity.this);
  7.  
  8.                 editText.setText(memolist.get(i));
  9.                 AlertDialog.Builder editDialog = new AlertDialog.Builder(ContentActivity.this);
  10.                 editDialog.setView(editText);
  11.                 editDialog.setTitle("请重新输入内容:");
  12.                 editDialog.setPositiveButton("确定", new DialogInterface.OnClickListener() {
  13.                     @Override
  14.                     public void onClick(DialogInterface dialogInterface, int i) {
  15.                         String newtitle = editText.getText().toString();
  16.                         if (newtitle.length() > 0) {
  17.                             myHelper.update_content(username, content, newtitle, db);
  18.                             Toast.makeText(ContentActivity.this, "数据已存入", Toast.LENGTH_LONG).show();
  19.                             onResume();
  20.                         } else {
  21.                             Toast.makeText(ContentActivity.this, "数据为空", Toast.LENGTH_LONG).show();
  22.                         }
  23.                     }
  24.                 });
  25.                 editDialog.show();
  26.             }
  27.         });

添加备忘录按钮：

  1.  //添加备忘录按键
  2.         button = findViewById(R.id.button);
  3.         button.setOnClickListener(new View.OnClickListener() {
  4.             @Override
  5.             public void onClick(View view) {
  6.                 final EditText editText = new EditText(ContentActivity.this);
  7.                 AlertDialog.Builder editalertlog = new AlertDialog.Builder(ContentActivity.this);
  8.                 editalertlog.setTitle("请输入备忘录内容:");
  9.                 editalertlog.setView(editText);
  10.                 editalertlog.setPositiveButton("确认", new DialogInterface.OnClickListener() {
  11.                     @Override
  12.                     public void onClick(DialogInterface dialogInterface, int i) {
  13.                         String title = editText.getText().toString();
  14.                         if(title.length()>0){
  15.                             myHelper.insert_title(username,title,db);
  16.                             Toast.makeText(ContentActivity.this,"数据已添加",Toast.LENGTH_LONG).show();
  17.                             onResume();
  18.                         }else {
  19.                             Toast.makeText(ContentActivity.this,"输入数据为空",Toast.LENGTH_LONG).show();
  20.                         }
  21.                     }
  22.                 });
  23.                 editalertlog.show();
  24.  
  25.             }
  26.         });

onResume()函数实时更新回调函数：

注意：这个回调函数涉及到界面备忘录数据的显示，另外listview 需要适配器，才能绑定数据

  1. @Override
  2.     protected void onResume() {
  3.         super.onResume();
  4.         if (db ==null || !db.isOpen()) {
  5.             db = myHelper.getWritableDatabase();
  6.         }
  7.             memolist = myHelper.queryMemo(username,db);
  8.             listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,memolist));
  9.  
  10.     }

全部代码：

MainActivity.java:

  1. ackage com.example.myapplication;
  2.  
  3. import androidx.appcompat.app.AppCompatActivity;
  4.  
  5. import android.content.Intent;
  6. import android.content.SharedPreferences;
  7. import android.database.sqlite.SQLiteDatabase;
  8. import android.graphics.drawable.Drawable;
  9. import android.os.Bundle;
  10. import android.text.method.PasswordTransformationMethod;
  11. import android.widget.Button;
  12. import android.widget.CheckBox;
  13. import android.widget.EditText;
  14. import android.widget.Toast;
  15.  
  16. public class MainActivity extends AppCompatActivity   {
  17.  
  18.     private EditText editText;
  19.     private EditText editText1;
  20.     Drawable icon;
  21.     Drawable icon1;
  22.     private CheckBox checkBox;
  23.  
  24.     private  MyHelper myHelper;
  25.  
  26.  
  27.     private SharedPreferences myShare;
  28.     private SQLiteDatabase db ;
  29.     private Button login;
  30.     private Button register;
  31.  
  32.     @Override
  33.     protected void onStart() {
  34.         super.onStart();
  35.         myShare = getSharedPreferences("save_login",MODE_PRIVATE);
  36.         Boolean checked = myShare.getBoolean("checkBox",false);
  37.         String name = myShare.getString("username",null);
  38.         String password = myShare.getString("password",null);
  39.         if(checked){
  40.             editText.setText("");
  41.             editText1.setText("");
  42.         }else{
  43.             editText.setText(name);
  44.             editText1.setText(password);
  45.         }
  46.  
  47.  
  48.  
  49.     }
  50.  
  51.  
  52.  
  53.  
  54.     @Override
  55.     protected void onStop() {
  56.         super.onStop();
  57.         //myHelper.closeLink();
  58.         myShare = getSharedPreferences("save_login",MODE_PRIVATE);
  59.         SharedPreferences.Editor myEdit = myShare.edit();
  60.         if(checkBox.isChecked()){
  61.  
  62.             myEdit.putString("username",editText.getText().toString());
  63.             myEdit.putString("password",editText1.getText().toString());
  64.             myEdit.putBoolean("checksave",true);
  65.             myEdit.commit();
  66.         }else {
  67.             myEdit.putBoolean("checksave",false);
  68.             myEdit.clear().commit();
  69.         }
  70.  
  71.     }
  72.  
  73.  
  74.     @Override
  75.     protected void onCreate(Bundle savedInstanceState) {
  76.         super.onCreate(savedInstanceState);
  77.         setContentView(R.layout.activity_main1);
  78.  
  79.         editText = findViewById(R.id.loginView);
  80.         editText1 = findViewById(R.id.passwordView);
  81.         editText1.setTransformationMethod(PasswordTransformationMethod.getInstance());//密码不可见
  82.  
  83.         icon = getResources().getDrawable(R.drawable.profile1);
  84.         icon1 = getResources().getDrawable(R.drawable.password);
  85.         icon.setBounds(0, 0, 80, 80);
  86.         editText.setCompoundDrawables(icon, null, null, null);
  87.         icon1.setBounds(0,0,80,80);
  88.         editText1.setCompoundDrawables(icon1, null, null, null);
  89.  
  90.         checkBox = findViewById(R.id.checkBox);
  91.  
  92.         myHelper = new MyHelper(MainActivity.this);
  93.         db = myHelper.getWritableDatabase();
  94.  
  95.         login = findViewById(R.id.loginbutton);
  96.         register = findViewById(R.id.registerbutton);
  97.         login.setOnClickListener(view -> {
  98.             user user = new user(editText.getText().toString(),editText1.getText().toString());
  99.  
  100.             if (myHelper.queryuser(user,db)){
  101.  
  102.                 Toast.makeText(MainActivity.this,"登陆成功",Toast.LENGTH_LONG).show();
  103.  
  104.                 Intent intent = new Intent(MainActivity.this,ContentActivity.class);
  105.                 intent.putExtra("username",editText.getText().toString());
  106.                 startActivity(intent);
  107.  
  108.             }else {
  109.                 Toast.makeText(MainActivity.this,"用户名或密码错误",Toast.LENGTH_LONG).show();
  110.             }
  111.         });
  112.  
  113.         register.setOnClickListener(view -> {
  114.             user user = new user(editText.getText().toString(),editText1.getText().toString());
  115.             myHelper.insert_user(user,db);
  116.             Toast.makeText(MainActivity.this,"注册成功",Toast.LENGTH_LONG).show();
  117.         });
  118.  
  119.  
  120.  
  121.  
  122.     }
  123.  
  124. }

ContentActivity.java

  1. package com.example.myapplication;
  2.  
  3. import androidx.appcompat.app.AlertDialog;
  4. import androidx.appcompat.app.AppCompatActivity;
  5.  
  6. import android.content.DialogInterface;
  7. import android.content.Intent;
  8. import android.database.sqlite.SQLiteDatabase;
  9. import android.os.Bundle;
  10. import android.view.View;
  11. import android.widget.AdapterView;
  12. import android.widget.ArrayAdapter;
  13. import android.widget.Button;
  14. import android.widget.EditText;
  15. import android.widget.ListView;
  16. import android.widget.TextView;
  17. import android.widget.Toast;
  18.  
  19. import java.util.ArrayList;
  20. import java.util.List;
  21.  
  22. public class ContentActivity extends AppCompatActivity {
  23.  
  24.     private ListView listView;
  25.     private String username;
  26.     private String title;
  27.     private MyHelper myHelper;
  28.     private SQLiteDatabase db;
  29.     private List<String> memolist = new ArrayList<>();
  30.     private Button button;
  31.     private TextView textView;
  32.  
  33.  
  34.     @Override
  35.     protected void onCreate(Bundle savedInstanceState) {
  36.         super.onCreate(savedInstanceState);
  37.         setContentView(R.layout.activity_content);
  38.         listView = findViewById(R.id.listview);
  39.         //接受MainActivity的传值
  40.         Intent intent = getIntent();
  41.         username = intent.getStringExtra("username");
  42.         myHelper =new MyHelper(this);
  43.         textView = findViewById(R.id.textView);
  44.         textView.setText(username+"的备忘录");
  45.  
  46.  
  47.  
  48.         //列表点击事件
  49.         //长按
  50.         listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
  51.             @Override
  52.             public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
  53.                 final String content = ((TextView) view).getText().toString();
  54.                 AlertDialog.Builder editDialog = new AlertDialog.Builder(ContentActivity.this);
  55.                 editDialog.setTitle(content);
  56.                 editDialog.setMessage("是否删除该备忘录");
  57.                 editDialog.setPositiveButton("确定", new DialogInterface.OnClickListener() {
  58.                     @Override
  59.                     public void onClick(DialogInterface dialogInterface, int i) {
  60.                         myHelper.delete_content(username, content, db);
  61.                         Toast.makeText(ContentActivity.this, "数据已删除", Toast.LENGTH_LONG).show();
  62.                         onResume();
  63.                     }
  64.                 });
  65.                 editDialog.show();
  66.                 return true;
  67.             }
  68.         });
  69.  
  70.         //短按事件
  71.         listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
  72.             @Override
  73.             public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
  74.                 final String content = ((TextView) view).getText().toString();
  75.                 final EditText editText = new EditText(ContentActivity.this);
  76.  
  77.                 editText.setText(memolist.get(i));
  78.                 AlertDialog.Builder editDialog = new AlertDialog.Builder(ContentActivity.this);
  79.                 editDialog.setView(editText);
  80.                 editDialog.setTitle("请重新输入内容:");
  81.                 editDialog.setPositiveButton("确定", new DialogInterface.OnClickListener() {
  82.                     @Override
  83.                     public void onClick(DialogInterface dialogInterface, int i) {
  84.                         String newtitle = editText.getText().toString();
  85.                         if (newtitle.length() > 0) {
  86.                             myHelper.update_content(username, content, newtitle, db);
  87.                             Toast.makeText(ContentActivity.this, "数据已存入", Toast.LENGTH_LONG).show();
  88.                             onResume();
  89.                         } else {
  90.                             Toast.makeText(ContentActivity.this, "数据为空", Toast.LENGTH_LONG).show();
  91.                         }
  92.                     }
  93.                 });
  94.                 editDialog.show();
  95.             }
  96.         });
  97.  
  98.         //添加备忘录按键
  99.         button = findViewById(R.id.button);
  100.         button.setOnClickListener(new View.OnClickListener() {
  101.             @Override
  102.             public void onClick(View view) {
  103.                 final EditText editText = new EditText(ContentActivity.this);
  104.                 AlertDialog.Builder editalertlog = new AlertDialog.Builder(ContentActivity.this);
  105.                 editalertlog.setTitle("请输入备忘录内容:");
  106.                 editalertlog.setView(editText);
  107.                 editalertlog.setPositiveButton("确认", new DialogInterface.OnClickListener() {
  108.                     @Override
  109.                     public void onClick(DialogInterface dialogInterface, int i) {
  110.                         String title = editText.getText().toString();
  111.                         if(title.length()>0){
  112.                             myHelper.insert_title(username,title,db);
  113.                             Toast.makeText(ContentActivity.this,"数据已添加",Toast.LENGTH_LONG).show();
  114.                             onResume();
  115.                         }else {
  116.                             Toast.makeText(ContentActivity.this,"输入数据为空",Toast.LENGTH_LONG).show();
  117.                         }
  118.                     }
  119.                 });
  120.                 editalertlog.show();
  121.  
  122.             }
  123.         });
  124.  
  125.  
  126.  
  127.  
  128.     }
  129.  
  130.     /**
  131.      *
  132.      */
  133.     @Override
  134.     protected void onResume() {
  135.         super.onResume();
  136.         if (db ==null || !db.isOpen()) {
  137.             db = myHelper.getWritableDatabase();
  138.         }
  139.             memolist = myHelper.queryMemo(username,db);
  140.             listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,memolist));
  141.  
  142.     }
  143.  
  144.     /**
  145.      *
  146.      */
  147.     @Override
  148.     protected void onStart() {
  149.         super.onStart();
  150.     }
  151.  
  152.     /**
  153.      *
  154.      */
  155.     @Override
  156.     protected void onStop() {
  157.         super.onStop();
  158.  
  159.  
  160.     }
  161. }

Myhelper.java

  1. package com.example.myapplication;
  2.  
  3. import android.annotation.SuppressLint;
  4. import android.content.Context;
  5. import android.database.Cursor;
  6. import android.database.sqlite.SQLiteDatabase;
  7. import android.database.sqlite.SQLiteOpenHelper;
  8. import android.widget.Toast;
  9.  
  10. import androidx.annotation.Nullable;
  11.  
  12. import java.util.ArrayList;
  13. import java.util.List;
  14.  
  15. public class MyHelper extends SQLiteOpenHelper {
  16.     private static final String dbname = "memo.db";
  17.     private static final  String UserTableName = "user_table";
  18.     private static  final  String ContentTableName = "content_table";
  19.     private List<String> memolist = new ArrayList<>();
  20.  
  21.     public MyHelper(@Nullable Context context) {
  22.         super(context,dbname, null, 2);
  23.     }
  24.  
  25.     @Override
  26.     public void onCreate(SQLiteDatabase sqLiteDatabase) {
  27.  
  28.         String sql_create1 = "CREATE TABLE IF NOT EXISTS "+ UserTableName +"("+"_id integer primary key autoincrement,username varchar not null,password varchar not null"+");";
  29.         sqLiteDatabase.execSQL(sql_create1);
  30.         String sql_create2 = "CREATE TABLE IF NOT EXISTS "+ ContentTableName +"("+"_id integer primary key autoincrement,username varchar not null,memotitle varchar not null"+");";
  31.         sqLiteDatabase.execSQL(sql_create2);
  32.  
  33.     }
  34.  
  35.  
  36.  
  37.     @Override
  38.     public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
  39.         String drop = "DROP TABLE IF EXISTS "+ UserTableName +";";
  40.         sqLiteDatabase.execSQL(drop);
  41.         drop = "DROP TABLE IF EXISTS "+ContentTableName +";";
  42.         sqLiteDatabase.execSQL(drop);
  43.         onCreate(sqLiteDatabase);
  44.  
  45.  
  46.     }
  47.  
  48.     //查询数据库 先按username 筛选记录 再与password字段匹配 ，如果不存在记录也是返回false
  49.     @SuppressLint("Range")
  50.     protected boolean queryuser(user user, SQLiteDatabase sqLiteDatabase){
  51.  
  52.         Cursor cursor = sqLiteDatabase.rawQuery("select * from user_table where username = ? and password = ?", new String[]{user.getUsername(), user.getPassword()});
  53.         if(cursor.moveToNext()) {
  54.  
  55.  
  56.             return true;
  57.  
  58.  
  59.         }
  60.         return false;
  61.     }
  62.     //注册事件 插入user记录
  63.     protected  void insert_user(user user,SQLiteDatabase sqLiteDatabase){
  64.         sqLiteDatabase.execSQL("insert into user_table "
  65.                         + "(username,password)"
  66.                         + "values(?,?)"  ,
  67.                 new String[]{user.getUsername(), user.getPassword()}
  68.         );
  69.  
  70.     }
  71.  
  72.     //查询备忘录并且返回list
  73.     protected  List<String> queryMemo(String username,SQLiteDatabase db){
  74.         memolist.clear();
  75.  
  76.         Cursor cursor = db.rawQuery("select * from content_table where username = ? ", new String[]{username});
  77.  
  78.         while (cursor.moveToNext()){
  79.             memolist.add(cursor.getString(2));
  80.         }
  81.  
  82.  
  83.  
  84.  
  85.         return memolist;
  86.     }
  87.  
  88.     //插入备忘录
  89.     protected void insert_title(String username ,String title ,SQLiteDatabase db){
  90.         db.execSQL("insert into content_table "
  91.                         + "(username,memotitle)"
  92.                         + "values(?,?)"  ,
  93.                 new String[]{username, title}
  94.         );
  95.     }
  96.  
  97.  
  98.     //删除备忘录
  99.     public void delete_content(String username ,String title ,SQLiteDatabase db){
  100.         String sql = "delete from "+ ContentTableName +" where username like '"+username+"' and memotitle like '"+title
  101.                 +"';";
  102.         db.execSQL(sql);
  103.     }
  104.  
  105.     //更新备忘录
  106.     public void update_content(String username,String old_tit,String new_tit,SQLiteDatabase db){
  107.         String sql = "update "+ ContentTableName +" set memotitle = '"+new_tit+"'where username like '"
  108.                 +username+"' and memotitle like '"+old_tit+"';";
  109.         db.execSQL(sql);
  110.     }
  111. }

user.java:

  1. package com.example.myapplication;
  2.  
  3. public class user {
  4.     private  String username;
  5.     private  String password;
  6.     public user(String username, String password){
  7.         this.username = username;
  8.         this.password = password;
  9.     }
  10.  
  11.     public String getUsername() {
  12.         return username;
  13.     }
  14.  
  15.     public String getPassword() {
  16.         return password;
  17.     }
  18. }

activity_content.xml:

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:orientation="vertical"
  8.     android:background="@drawable/background"
  9.     android:gravity="center"
  10.     tools:context=".ContentActivity">
  11.  
  12.     <TextView
  13.         android:id="@+id/textView"
  14.         android:layout_width="401dp"
  15.         android:layout_height="39dp"
  16.         android:text="备忘录"
  17.         android:textAlignment="center"
  18.         android:textAppearance="@style/TextAppearance.AppCompat.Large" />
  19.  
  20.     <ListView
  21.         android:id="@+id/listview"
  22.         android:layout_width="398dp"
  23.         android:layout_height="613dp" />
  24.  
  25.     <Button
  26.         android:id="@+id/button"
  27.         android:layout_width="wrap_content"
  28.         android:layout_height="65dp"
  29.         android:background="@android:drawable/ic_input_add"
  30.         android:backgroundTint="#E1D0D0"
  31.         app:rippleColor="@color/white" />
  32. </LinearLayout>

activity_main.xml

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:background="@drawable/img"
  8.     tools:context=".MainActivity">
  9.  
  10.     <ImageView
  11.         android:id="@+id/imageView"
  12.         android:layout_width="122dp"
  13.         android:layout_height="109dp"
  14.         android:layout_marginStart="152dp"
  15.         android:layout_marginBottom="44dp"
  16.         android:src="@drawable/userimg"
  17.         app:layout_constraintBottom_toTopOf="@+id/loginView"
  18.         app:layout_constraintStart_toStartOf="parent" />
  19.  
  20.     <EditText
  21.         android:id="@+id/loginView"
  22.         android:layout_width="235dp"
  23.         android:layout_height="51dp"
  24.         android:layout_marginStart="108dp"
  25.         android:layout_marginTop="232dp"
  26.         android:background="@android:drawable/editbox_background"
  27.         android:hint=" Enter your name"
  28.         app:layout_constraintStart_toStartOf="parent"
  29.         app:layout_constraintTop_toTopOf="parent" />
  30.  
  31.     <EditText
  32.         android:id="@+id/passwordView"
  33.         android:layout_width="240dp"
  34.         android:layout_height="50dp"
  35.         android:layout_marginStart="104dp"
  36.         android:layout_marginTop="36dp"
  37.         android:background="@android:drawable/editbox_background"
  38.         android:hint=" Enter your password"
  39.         app:layout_constraintStart_toStartOf="parent"
  40.         app:layout_constraintTop_toBottomOf="@+id/loginView" />
  41.  
  42.     <Button
  43.         android:id="@+id/loginbutton"
  44.         android:layout_width="wrap_content"
  45.         android:layout_height="wrap_content"
  46.         android:layout_marginStart="84dp"
  47.         android:layout_marginTop="144dp"
  48.         android:text="登录"
  49.         app:layout_constraintStart_toStartOf="parent"
  50.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  51.  
  52.     <Button
  53.         android:id="@+id/registerbutton"
  54.         android:layout_width="wrap_content"
  55.         android:layout_height="wrap_content"
  56.         android:layout_marginTop="144dp"
  57.         android:layout_marginEnd="40dp"
  58.         android:text="注册"
  59.         app:layout_constraintEnd_toEndOf="parent"
  60.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  61.  
  62.     <CheckBox
  63.         android:id="@+id/checkBox"
  64.         android:layout_width="wrap_content"
  65.         android:layout_height="wrap_content"
  66.         android:layout_marginTop="68dp"
  67.         android:layout_marginEnd="36dp"
  68.         android:text="记住密码"
  69.         android:textAppearance="@style/TextAppearance.AppCompat.Medium"
  70.         app:layout_constraintEnd_toEndOf="parent"
  71.         app:layout_constraintTop_toBottomOf="@+id/passwordView" />
  72.  
  73. </androidx.constraintlayout.widget.ConstraintLayout>

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