Android数据库操作类，超实用！

android代码分享第三弹：超实用的数据库操作类！在书里看到的，整理出来了，在原来的基础上又加了几个函数，并且新建数据库的那边也做了更改，判断所在目录有没有。最初使用时候经常发生错误，不能在程序私有空间建立数据库文件，后来才发现是路径问题，改了一下，从此有权限的地方都能建库！so easy!在查询那边加了一个用sql语句进行查询的函数，原来的那个函数不会用，还是直接sql方便。加了个复制数据库的函数。准备好数据库放在raw目录下，到时候用R.raw访问。

不多说，看代码：

package czd.android.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class SQLiteUtil {

    public static final String SQLite_MASTER_TABLE = "sqlite_master";
    private static SQLiteUtil mInstance = new SQLiteUtil();

    /**
     *
     */
    private SQLiteUtil() {
    }

    /**
     * @return instance of SQLiteUtil
     */
    public static SQLiteUtil getInstance() {
        return SQLiteUtil.mInstance;
    }

    /**
     * open or create a database with the given dbName:
     * /data/data/packagename/databases/databasefilename
     * /sdcard/databasefilename
     *
     * @param dbName
     * @return SQLiteDatabase
     */
    private SQLiteDatabase openDB(String dbName) {
        File file = new File(dbName);
        if (file.exists() == true) {
            return SQLiteDatabase.openDatabase(dbName, null, SQLiteDatabase.OPEN_READWRITE);
        }else {
            File datafiledir = file.getParentFile();
            if(!datafiledir.exists()){
                datafiledir.mkdirs();
            }
            return SQLiteDatabase.openOrCreateDatabase(dbName, null);
        }
    }

    /**
     * close database
     *
     * @param db
     */
    private void closeDB(SQLiteDatabase db) {
        db.close();
    }

    /**
     * delete database
     *
     * @param dbName
     * @return boolean
     */
    public boolean deleteDB(String dbName) {
        File file = new File(dbName);
        if (file.exists() == true) {
            return file.delete();
        }
        return true;
    }

    /**
     * execute sql command
     *
     * @param dbName
     * @param sql
     */
    public void execQuery(String dbName, String sql) {
        SQLiteDatabase db = openDB(dbName);
        db.execSQL(sql);
        closeDB(db);
    }

    /**
     * execute sql command and return Cursor
     *
     * @param dbName
     * @param tableName
     * @param condStr
     * @return Cursor
     */
    public Cursor openQuery(String dbName, String sql) {
        SQLiteDatabase db = openDB(dbName);
        Cursor cursor = db.rawQuery(sql, null);
        cursor.moveToFirst();
        closeDB(db);
        return cursor;
    }

    public Cursor openQuery(String dbName, String tableName, String condStr) {
        SQLiteDatabase db = openDB(dbName);
        Cursor cursor = db.query(tableName, null, condStr, null, null, null, null);
        cursor.moveToFirst();
        closeDB(db);
        return (cursor);
    }

    public int getRowsCount(Cursor cursor) {
        return cursor.getCount();
    }

    public int getColumnsCount(Cursor cursor) {
        return cursor.getColumnCount();
    }

    public String getColumnNameBy(Cursor cursor, int index) {
        return cursor.getColumnName(index);
    }

    public boolean isBOF(Cursor cursor) {
        return cursor.isBeforeFirst();
    }

    public boolean isEOF(Cursor cursor) {
        return cursor.isAfterLast();
    }

    public boolean moveNext(Cursor cursor) {
        return cursor.moveToNext();
    }

    public String getField(Cursor cursor, int index) {
        return cursor.getString(index);
    }

    public void closeQuery(Cursor cursor) {
        cursor.close();
    }

    public boolean isTableExists(String dbName, String tableName) {
        Cursor cursor = openQuery(dbName, SQLite_MASTER_TABLE, "(tbl_name='" + tableName + "')");
        int recordCount = cursor.getCount();
        cursor.close();
        return (recordCount > 0);
    }

    public boolean isDatabaseExists(String dbName){
        return new File(dbName).exists();
    }

    public static void copyDatabase(Context context, String dbName, int resourceId) {
        try {
            if (!(new File(dbName)).exists()) {
                InputStream is = context.getResources().openRawResource(resourceId);
                FileOutputStream fos = new FileOutputStream(dbName);
                byte[] buffer = new byte[1024];
                int count = 0;
                while ((count = is.read(buffer)) > 0) {
                    fos.write(buffer, 0, count);
                }
                fos.close();
                is.close();
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
    }
};