alexkn android第一行代码－8.sqlite使用

Android自带sqlite数据库，因此常见操作应该都掌握。包括数据库的创建/升级以及增删改查。

1.创建数据库

public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String CREATE_BOOK = "create table book ("
            + "id integer primary key autoincrement, "
            + "author text,"
            + "price real,"
            + "page integer,"
            + "name text)";

    private Context mContext;

    public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        mContext = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_BOOK);
        Toast.makeText(mContext,"Create succeeded",Toast.LENGTH_SHORT).show();
    }
}

创建数据库的类完成后，绑定事件触发即可

public class MainActivity extends AppCompatActivity {

    private MyDatabaseHelper dbHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,1);
        Button createDatabase = (Button) findViewById(R.id.create_database);

        createDatabase.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dbHelper.getWritableDatabase();
            }
        });

    }
    
}

2.数据库升级

假设新增一张表，

首先更新版本

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

然后重写onUpgrade方法

public class MyDatabaseHelper extends SQLiteOpenHelper {

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

3.添加数据（insert）

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
     ...
    <Button
        android:id="@+id/add_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add data"/>
</LinearLayout>

public class MainActivity extends AppCompatActivity {

    private MyDatabaseHelper dbHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,2);
　　　　　...
        Button addData = (Button) findViewById(R.id.add_data);

        addData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                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); // 插入第一条数据
                values.clear();

                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); // 插入第二条数据
            }
        });
    }
} 

4.删除数据（delete）

跟3一致，除了db的调用方法不一致

db.delete("Book", "pages > ?", new String[] { "500" });

5.修改数据（update）

db.update("Book", values, "name = ?", new String[] { "The DaVinci Code" });

6.查询数据（search）

查询比较复杂，需要7个参数

        queryButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                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"));
                        Log.d("MainActivity", "book name is " + name);
                        Toast.makeText(MainActivity.this,"book name is "+name,Toast.LENGTH_SHORT).show();
                        Log.d("MainActivity", "book author is " + author);
                        Log.d("MainActivity", "book pages is " + pages);
                        Log.d("MainActivity", "book price is " + price);
                    } while (cursor.moveToNext());
                }
                cursor.close();
            }
        });

7.原生操作

// 添加数据的方法如下：
db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)", new String[] { "The Da Vinci Code", "Dan Brown", "454", "16.96" }); db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)", new String[] { "The Lost Symbol", "Dan Brown", "510", "19.95" });

// 更新数据的方法如下:
db.execSQL("update Book set price = ? where name = ?", new String[] { "10.99", "The Da Vinci Code" });

// 删除数据的方法如下:
db.execSQL("delete from Book where pages > ?", new String[] { "500" });

// 查询数据的方法如下:
db.rawQuery("select * from Book", null);