Android SQLite使用

时间  2019-11-12
标签 android sqlite 使用 栏目 Android 繁體版
原文   原文链接

1、Cursor的使用

使用Cursor实现增删改查功能java

使用Cursor增长和修改：android

ContentValues values = new ContentValues();
values.put(RadioDbConst.RadioStation.BAND, station.getBand());
values.put(RadioDbConst.RadioStation.FREQUENCY, station.getFrequencyStr());
values.put(RadioDbConst.RadioStation.IS_STERO, station.isStereoInt());
values.put(RadioDbConst.RadioStation.TYPE, station.getType());

ContentResolver resolver = mContext.getContentResolver();
StationInfo mInfo = getCollectStation(station.getBand(), station.getFrequencyStr());
if (null != mInfo) {
	Log.i(TAG, "collect -- has");
	if (mInfo.getType() != 2 || mInfo.isStereoInt() != station.isStereoInt()) {
		Log.i(TAG, "collect -- update");
		String selection = RadioDbConst.RadioStation.TYPE + " = ?" + " and " + RadioDbConst.RadioStation.IS_STERO + " ?";
		String[] selectionArgs = { String.valueOf(2), String.valueOf(station.isStereoInt()) };
		resolver.update(RadioProvider.CONTENT_URI_COLLECT, values, selection, selectionArgs);
	}
} else {
	Log.i(TAG, "collect -- insert value:" + values.getAsString(RadioDbConst.SavedStation.FREQUENCY));
	resolver.insert(RadioProvider.CONTENT_URI_COLLECT, values);
}

 

 

使用Cursor删除：sql

int id = mContext.getContentResolver().delete(RadioProvider.CONTENT_URI_RADIO_STATION, selection, selectionArgs);

 

 

使用Cursor查询：数据库

String selection = RadioDbConst.RadioStation.BAND + " = ? " + "and" + RadioDbConst.RadioStation.FREQUENCY + " = ?";
String[] selectionArgs = { fre };
StationInfo si = null;
Cursor cursor = mContext.getContentResolver().query(RadioProvider.CONTENT_URI_COLLECT, null, selection, selectionArgs, null);
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
	int b = cursor.getInt(cursor.getColumnIndex(RadioDbConst.RadioStation.IS_STERO));
	int type = cursor.getInt(cursor.getColumnIndex(RadioDbConst.RadioStation.TYPE));
	si = new StationInfo(band, fre, b, type);
	Log.e("si", si.toString());
}
cursor.close();

2、DBHelper

1.构造函数ide

private Context mContext;

public DatabaseHelper(Context context, String name, CursorFactory factory, int version) {
	// 必须经过super调用父类当中的构造函数
	super(context, name, null, version);
	mContext = context;

	try {
		createDataBase();
	} catch (IOException e) {
		e.printStackTrace();
	}
}

public DatabaseHelper(Context context, String name, int version) {
	this(context, name, null, version);
}

public DatabaseHelper(Context context, String name) {
	this(context, name, StaticCode.DATABASE_VERSION);
}

public DatabaseHelper(Context context) {
	this(context, StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME);
}

2.检查数据库是否有效函数

/**
 * 检查数据库是否有效
 * 
 * @return
 */
private boolean checkDataBase() {
	SQLiteDatabase checkDB = null;
	boolean isCecked = false;
	String myPath = StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME;
	try {
		checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
		if (checkDB != null) {
			checkDB.close();
			isCecked = true;
		}
	} catch (Exception e) {

	}

	return isCecked;
}

3.建立数据库大数据

public void createDataBase() throws IOException {
	boolean dbExist = checkDataBase();
	if (dbExist) {
		// 数据库已存在，do nothing.
	} else {
		// 建立数据库
		File dir = new File(StaticCode.DATABASE_FILEPATH);
		if (!dir.exists()) {
			dir.mkdirs();
		}
		File dbf = new File(StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME);
		if (dbf.exists()) {
			dbf.delete();
		}
		SQLiteDatabase.openOrCreateDatabase(dbf, null);
	}
}

4.将本地资源文件夹中的数据库复制到刚刚建立的空数据库this

/**
 * Copies your database from your local assets-folder to the just created empty database in the
 * system folder, from where it can be accessed and handled.
 * This is done by transfering bytestream.
 * */
private void copyDataBase() throws IOException{
	//Open your local db as the input stream
	InputStream myInput = myContext.getAssets().open(ASSETS_NAME);
	// Path to the just created empty db
	String outFileName = DB_PATH + DB_NAME;
	//Open the empty db as the output stream
	OutputStream myOutput = new FileOutputStream(outFileName);
	//transfer bytes from the inputfile to the outputfile
	byte[] buffer = new byte[1024];
	int length;
	while ((length = myInput.read(buffer))>0){
		myOutput.write(buffer, 0, length);
	}
	//Close the streams
	myOutput.flush();
	myOutput.close();
	myInput.close();
}

//复制assets下的大数据库文件时用这个
private void copyBigDataBase() throws IOException{
	InputStream myInput;
	String outFileName = DB_PATH + DB_NAME;
	OutputStream myOutput = new FileOutputStream(outFileName);
	for (int i = ASSETS_SUFFIX_BEGIN; i < ASSETS_SUFFIX_END+1; i++) {
		myInput = myContext.getAssets().open(ASSETS_NAME + "." + i);
		byte[] buffer = new byte[1024];
		int length;
		while ((length = myInput.read(buffer))>0){
			myOutput.write(buffer, 0, length);
		}
		myOutput.flush();
		myInput.close();
	}
	myOutput.close();
}

 注意：spa

    execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了好久才明白，见execSQL的源码注释 (Multiple statements separated by ;s are not supported.).net

    将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M如下， 若是有超过1M的大文件，则须要先分割为N个小文件，而后使用copyBigDatabase()替换copyDatabase()

5.建立表

db.execSQL("CREATE TABLE IF NOT EXISTS "
                + RadioDbConst.RadioStation.TABLE_NAME + " ("
                + RadioDbConst.RadioStation._ID
                + " integer primary key autoincrement,"
                + RadioDbConst.RadioStation.FREQUENCY + " text,"
                + RadioDbConst.RadioStation.TITLE + " text,"
                + RadioDbConst.RadioStation.BAND + " integer,"
                + RadioDbConst.RadioStation.IS_STERO + " integer,"
                + RadioDbConst.RadioStation.TYPE + " integer);");

6.Android 将数据库文件保存至sdcard中

3、Android SQLite数据库(dictionary.db文件)与apk文件一块儿发布

4、数据库处理

package cn.arthur.common;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * @author Joshua
 * 用法：
 * DBHelper dbHelper = new DBHelper(this);
 * dbHelper.createDataBase();
 * SQLiteDatabase db = dbHelper.getWritableDatabase();
 * Cursor cursor = db.query()
 * db.execSQL(sqlString);
 * 注意：execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了好久才明白
 * 见execSQL的源码注释 (Multiple statements separated by ;s are not supported.)
 * 将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M如下
 * 若是有超过1M的大文件，则须要先分割为N个小文件，而后使用copyBigDatabase()替换copyDatabase()
 */
 public class DBHelper extends SQLiteOpenHelper {
 //用户数据库文件的版本
 private static final int DB_VERSION    = 1;
      //数据库文件目标存放路径为系统默认位置，cn.arthur.examples 是你的包名
      private static String DB_PATH        = "/data/data/cn.arthur.examples/databases/";
  /*
      //若是你想把数据库文件存放在SD卡的话
      private static String DB_PATH        = android.os.Environment.getExternalStorageDirectory().getAbsolutePath()
                                          + "/arthurcn/drivertest/packfiles/";
  */
      private static String DB_NAME         = "hello.db";
     private static String ASSETS_NAME     = "hello.db";
  
      private SQLiteDatabase myDataBase    = null;
      private final Context myContext;
  
       /** 
        * 若是数据库文件较大，使用FileSplit分割为小于1M的小文件
        * 此例中分割为 hello.db.101    hello.db.102    hello.db.103
        */
      //第一个文件名后缀
      private static final int ASSETS_SUFFIX_BEGIN    = 101;
      //最后一个文件名后缀
      private static final int ASSETS_SUFFIX_END        = 103;
      
      /**
       * 在SQLiteOpenHelper的子类当中，必须有该构造函数
       * @param context    上下文对象
       * @param name        数据库名称
       * @param factory    通常都是null
       * @param version    当前数据库的版本，值必须是整数而且是递增的状态
       */
      public DBHelper(Context context, String name, CursorFactory factory, int version) {
          //必须经过super调用父类当中的构造函数
          super(context, name, null, version);
          this.myContext = context;
      }
      
      public DBHelper(Context context, String name, int version){
          this(context,name,null,version);
      }
  
      public DBHelper(Context context, String name){
          this(context,name,DB_VERSION);
      }
      
      public DBHelper (Context context) {
          this(context, DB_PATH + DB_NAME);
      }
      
      public void createDataBase() throws IOException{
          boolean dbExist = checkDataBase();
          if(dbExist){
              //数据库已存在，do nothing.
          }else{
              //建立数据库
              try {
                  File dir = new File(DB_PATH);
                  if(!dir.exists()){
                      dir.mkdirs();
                  }
                  File dbf = new File(DB_PATH + DB_NAME);
                  if(dbf.exists()){
                      dbf.delete();
                  }
                  SQLiteDatabase.openOrCreateDatabase(dbf, null);
                  // 复制asseets中的db文件到DB_PATH下
                  copyDataBase();
              } catch (IOException e) {
                  throw new Error("数据库建立失败");
              }
          }
     }
     
     //检查数据库是否有效
     private boolean checkDataBase(){
         SQLiteDatabase checkDB = null;
         String myPath = DB_PATH + DB_NAME;
         try{            
             checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
         }catch(SQLiteException e){
             //database does't exist yet.
         }
         if(checkDB != null){
             checkDB.close();
         }
          return checkDB != null ? true : false;
     }
  
     /**
      * Copies your database from your local assets-folder to the just created empty database in the
      * system folder, from where it can be accessed and handled.
      * This is done by transfering bytestream.
      * */
     private void copyDataBase() throws IOException{
         //Open your local db as the input stream
         InputStream myInput = myContext.getAssets().open(ASSETS_NAME);
         // Path to the just created empty db
         String outFileName = DB_PATH + DB_NAME;
         //Open the empty db as the output stream
         OutputStream myOutput = new FileOutputStream(outFileName);
         //transfer bytes from the inputfile to the outputfile
         byte[] buffer = new byte[1024];
         int length;
         while ((length = myInput.read(buffer))>0){
             myOutput.write(buffer, 0, length);
         }
         //Close the streams
         myOutput.flush();
         myOutput.close();
         myInput.close();
     }
     
     //复制assets下的大数据库文件时用这个
     private void copyBigDataBase() throws IOException{
         InputStream myInput;
         String outFileName = DB_PATH + DB_NAME;
         OutputStream myOutput = new FileOutputStream(outFileName);
         for (int i = ASSETS_SUFFIX_BEGIN; i < ASSETS_SUFFIX_END+1; i++) {
             myInput = myContext.getAssets().open(ASSETS_NAME + "." + i);
             byte[] buffer = new byte[1024];
             int length;
             while ((length = myInput.read(buffer))>0){
                 myOutput.write(buffer, 0, length);
             }
             myOutput.flush();
             myInput.close();
         }
         myOutput.close();
     }
     
     @Override
     public synchronized void close() {
         if(myDataBase != null){
             myDataBase.close();
         }
         super.close();
     }
     
     /**
      * 该函数是在第一次建立的时候执行，
      * 其实是第一次获得SQLiteDatabase对象的时候才会调用这个方法
      */
     @Override
     public void onCreate(SQLiteDatabase db) {
     }
     
     /**
      * 数据库表结构有变化时采用
      */
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
     }
 
}
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