sqlite 数据库封装类

DatabaseUtil.java(封装的类)

package com.jack.androidbase.tools;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * sqlite 数据库操作类
 */
public class DatabaseUtil {

    private static final String TAG = "DatabaseUtil";

    /**
     * Database Name
     */
    private static final String DATABASE_NAME = "student_data";

    /**
     * Database Version
     */
    private static final int DATABASE_VERSION = 1;

    /**
     * Table Name
     */
    private static final String DATABASE_TABLE = "tb_student";

    /**
     * Table columns
     */
    public static final String KEY_NAME = "name";
    public static final String KEY_GRADE = "grade";
    public static final String KEY_ROWID = "_id";

    /**
     * Database creation sql statement
     */
    private static final String CREATE_TABLE =
            "create table " + DATABASE_TABLE + " (" + KEY_ROWID + " integer primary key autoincrement, "
                    + KEY_NAME + " text not null, " + KEY_GRADE + " text not null);";

    /**
     * Context
     */
    private final Context mCtx;

    private DatabaseHelper mDbHelper;
    private SQLiteDatabase mDb;

    /**
     * Inner private class. Database Helper class for creating and updating database.
     */
    private static class DatabaseHelper extends SQLiteOpenHelper {
        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        /**
         * onCreate method is called for the 1st time when database doesn't exists.
         */
        @Override
        public void onCreate(SQLiteDatabase db) {
            Log.i(TAG, "Creating DataBase: " + CREATE_TABLE);
            db.execSQL(CREATE_TABLE);
        }

        /**
         * onUpgrade method is called when database version changes.
         */
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion);
        }
    }

    /**
     * Constructor - takes the context to allow the database to be
     * opened/created
     *
     * @param ctx the Context within which to work
     */
    public DatabaseUtil(Context ctx) {
        this.mCtx = ctx;
    }

    /**
     * This method is used for creating/opening connection
     *
     * @return instance of DatabaseUtil
     * @throws SQLException
     */
    public DatabaseUtil open() throws SQLException {
        mDbHelper = new DatabaseHelper(mCtx);
        mDb = mDbHelper.getWritableDatabase();
        return this;
    }

    /**
     * This method is used for closing the connection.
     */
    public void close() {
        mDbHelper.close();
    }

    /**
     * This method is used to create/insert new record record.
     *
     * @param name
     * @param grade
     * @return long
     */
    public long insert(String name, String grade) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_NAME, name);
        initialValues.put(KEY_GRADE, grade);
        return mDb.insert(DATABASE_TABLE, null, initialValues);
    }

    /**
     * This method will delete record.
     *
     * @param rowId
     * @return boolean
     */
    public boolean delete(long rowId) {
        return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
    }

    /**
     * This method will deleteAll record.
     *
     * @return
     */
    public boolean deleteAll() {
        return mDb.delete(DATABASE_TABLE, " 1 ", null) > 0;
    }

    /**
     * This method will return Cursor holding all the records.
     *
     * @return Cursor
     */
    public Cursor fetchAll() {
        return mDb.query(DATABASE_TABLE, new String[]{KEY_ROWID, KEY_NAME,
                KEY_GRADE}, null, null, null, null, null);
    }

    /**
     * This method will return Cursor holding the specific record.
     *
     * @param id
     * @return Cursor
     * @throws SQLException
     */
    public Cursor fetch(long id) throws SQLException {
        Cursor mCursor =
                mDb.query(true, DATABASE_TABLE, new String[]{KEY_ROWID,
                                KEY_NAME, KEY_GRADE}, KEY_ROWID + "=" + id, null,
                        null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    /**
     * This method will update record.
     *
     * @param id
     * @param name
     * @param standard
     * @return boolean
     */
    public boolean update(int id, String name, String standard) {
        ContentValues args = new ContentValues();
        args.put(KEY_NAME, name);
        args.put(KEY_GRADE, standard);
        return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + id, null) > 0;
    }
}

使用详解：

DatabaseUtil dbUtil = new DatabaseUtil(this);
        dbUtil.open();

        switch (v.getId()) {
            case R.id.other_btn_sqlite_list: //查询
                Cursor cursor = dbUtil.fetchAll();
                if (cursor != null) {
                    while (cursor.moveToNext()) {
                        Log.i(“Student”, “ID:” + cursor.getInt(0) + “,Student Name: ” + cursor.getString(1) +
                                “,Grade: ” + cursor.getString(2));
                    }
                }
                break;
            case R.id.other_btn_sqlite_add:
                dbUtil.insert(“Prashant Thakkar”, “100”);
                Log.i(“Student”, “add over”);
                break;
            case R.id.other_btn_sqlite_update:
                dbUtil.update(1, “aa”, “bb”);
                Log.i(“Student”, “update over”);
                break;
            case R.id.other_btn_sqlite_del:
                dbUtil.delete(2);
                Log.i(“Student”, “delete over”);
                break;
            case R.id.other_btn_sqlite_del_all:
                dbUtil.deleteAll();
                Log.i(“Student”, “delete all over”);
                break;
        }
        dbUtil.close();

 参考网址：

https://www.cnblogs.com/sowhat4999/p/4439856.html

https://www.cnblogs.com/ProMonkey/p/5765616.html   (有添加单例模式)

本博客地址： wukong1688

本文原文地址：https://www.cnblogs.com/wukong1688/p/10666280.html

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