Android的SQLite数据存储

创建数据库

public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String CREATE_BOOK = "create table Book("
            +"id integer primary key autoincrement,"
            +"autor text,"
            +"price real,"
            +"pages integer,"
            +"name text)";
    private Context mContext;
    public MyDatabaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        mContext = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //执行SQL语句
        db.execSQL(CREATE_BOOK);
        Toast.makeText(mContext,"Create succeed",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.button);
        Button button1 = findViewById(R.id.button_read);
        Button button2 = findViewById(R.id.button_table);
        final EditText editText = findViewById(R.id.edit_text);
        final TextView textView = findViewById(R.id.text_view);


        final MyDatabaseHelper dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,1);

        //创建数据库和表
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //调用该方法，线查看是否有BookStroe数据库，如果没有，就创建，并调用onCreate()方法，创建数据库表
                dbHelper.getWritableDatabase();
            }
        });
    }
    
}

如果还要再创建一个表时，不能直接在onCreate()里面添加，因为已经创建了一个数据库，不会再创建数据库，不会执行onCreate()方法，因此需要重写onUpgrade()方法，并该传入的版本号

public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String CREATE_BOOK = "create table Book("
            +"id integer primary key autoincrement,"
            +"autor text,"
            +"price real,"
            +"pages integer,"
            +"name text)";
    //创建第二个表
    public static final String CREATE_CATEGORY = "create table Catagory("
            +"id integer primary key autoincrement,"
            +"category_name text," +
            "category_code integer)";
    private Context mContext;
    public MyDatabaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        mContext = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //执行SQL语句
        db.execSQL(CREATE_BOOK);
        db.execSQL(CREATE_CATEGORY);
        Toast.makeText(mContext,"Create succeed",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("drop table if exists Book");
        db.execSQL("drop table if exists Category");
        onCreate(db);
    }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.button);
        Button button1 = findViewById(R.id.button_read);
        Button button2 = findViewById(R.id.button_table);
        final EditText editText = findViewById(R.id.edit_text);
        final TextView textView = findViewById(R.id.text_view);


        final MyDatabaseHelper dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,2);

        //创建数据库和表
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //调用该方法，线查看是否有BookStroe数据库，如果没有，就创建，并调用onCreate()方法，创建数据库表
                dbHelper.getWritableDatabase();
            }
        });
    }

}

数据的增删查改

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


   <TextView
       android:id="@+id/text_view"
       android:lines="20"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
   <Button
       android:text="存储"
       android:id="@+id/button"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>

   <Button
       android:text="读取"
       android:id="@+id/button_read"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
   <Button
       android:text="创建数据库表"
       android:id="@+id/button_table"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>

   <Button
       android:text="删除"
       android:id="@+id/button_delete"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
   <Button
       android:text="更新"
       android:id="@+id/button_update"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
</LinearLayout>

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.button);
        Button button1 = findViewById(R.id.button_read);
        Button button2 = findViewById(R.id.button_table);
        Button update = findViewById(R.id.button_update);
        Button delete = findViewById(R.id.button_delete);
        final TextView textView = findViewById(R.id.text_view);


        final MyDatabaseHelper dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,3);

        //创建数据库和表
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //调用该方法，线查看是否有BookStroe数据库，如果没有，就创建，并调用onCreate()方法，创建数据库表
                dbHelper.getWritableDatabase();
            }
        });

        //存储数据
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                //组装第一条数据
                values.put("name","The Da Vinci Code");
                values.put("author","Dan Brown");
                values.put("pages",454);
                values.put("price",16.96);
                db.insert("Book",null, values);
                values.clear();
                //组装第二条数据
                values.put("name","The Lost Symbol");
                values.put("author","Dan Brown");
                values.put("pages",510);
                values.put("price",19.95);
                db.insert("Book",null,values);
                values.clear();
                values.put("name","hello,world");
                values.put("author","Dan Brown");
                values.put("pages",250);
                values.put("price",20.95);
                db.insert("Book",null,values);
            }
        });

        //查询数据
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textView.setText("");
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                Cursor cursor = db.query("Book",null,null,
                        null,null,null,null);
                if(cursor.moveToFirst()){
                    do{
                        String name = cursor.getString(cursor.getColumnIndex("name"));
                        String author = cursor.getString(cursor.getColumnIndex("author"));
                        int  pages = cursor.getInt(cursor.getColumnIndex("pages"));
                        double price = cursor.getDouble(cursor.getColumnIndex("price"));
                        textView.append(name+" "+author+" "+pages+" "+price+"\n");
                    }while(cursor.moveToNext());
                }
                cursor.close();
            }
        });

        //更新数据
        update.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                values.put("price",10.99);
                db.update("Book",values,"name=?",new String[]{"The Da Vinci Code"});
            }
        });


        //删除数据
       delete.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               SQLiteDatabase db = dbHelper.getWritableDatabase();
               //删除页数大于500的
               db.delete("Book","pages > ?",new String[]{"500"});
           }
       });
    }

}