Android Sqlite數據庫增刪改查應用

一、Sqlite數據庫介紹

二、Sqlite數據庫增刪改查在Android開發中應用

Sqlite數據庫數據常用類型介紹

1、每個存儲在 SQLite 數據庫中的值都具有以下存儲類之一：

NULL ：值是一個 NULL 值。

INTEGER: 值是一個帶符號的整數，根據值的大小存儲在 1、2、3、4、6 或 8 字節中。

REAL : 值是一個浮點值，存儲爲 8 字節的 IEEE 浮點數字

TEXT:值是一個文本字符串，使用數據庫編碼（UTF-8、UTF-16BE 或 UTF-16LE）存儲

BLOB:值是一個 blob 數據，完全根據它的輸入存儲。

2、Sqlite親和類型

親和類型	描述
TEXT	數值型數據在被插入之前，需要先被轉換爲文本格式，之後再插入到目標字段中。
NUMERIC	當文本數據被插入到親緣性爲NUMERIC的字段中時，如果轉換操作不會導致數據信息丟失以及完全可逆，那麼SQLite就會將該文本數據轉換爲INTEGER或REAL類型的數據，如果轉換失敗，SQLite仍會以TEXT方式存儲該數據。對於NULL或BLOB類型的新數據，SQLite將不做任何轉換，直接以NULL或BLOB的方式存儲該數據。需要額外說明的是，對於浮點格式的常量文本，如"30000.0"，如果該值可以轉換爲INTEGER同時又不會丟失數值信息，那麼SQLite就會將其轉換爲INTEGER的存儲方式。
INTEGER	對於親緣類型爲INTEGER的字段，其規則等同於NUMERIC，唯一差別是在執行CAST表達式時。
REAL	其規則基本等同於NUMERIC，唯一的差別是不會將"30000.0"這樣的文本數據轉換爲INTEGER存儲方式。
NONE	不做任何的轉換，直接以該數據所屬的數據類型進行存儲。

INTEGER : INT , INTEGER ,TINYINT , SMALLINT ,MEDIUMINT ,BIGINT ,UNSIGNED BIG INT ,INT2 ,INT8

TEXT: CHARACTER(20) 、VARCHAR(255)、VARYING CHARACTER(255)、NCHAR(55)、NATIVE CHARACTER(70)、NVARCHAR(100)、TEXT、CLOB

NONE：BLOB no datatype specified

REAL：REAL、DOUBLE、DOUBLE PRECISION、FLOAT

NUMERIC：NUMERIC、DECIMAL(10,5)、BOOLEAN、DATE、DATETIME

SQLite 沒有單獨的 Boolean 存儲類。相反，布爾值被存儲爲整數 0（false）和 1（true）。

Sqlite數據庫在Android應用中使用

Android 平臺內置了豐富的API可以供開發者調用SQLIte數據庫

1、首先繼承 SQLiteOpenHelper 類並實現裏面的 onCreate(SQLiteDatabase db)方法和 onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)

onCreate 方法是應用程創建數據庫及其表

onUpgrade 數據庫版更新調用

2、創建一個單例類 LeDBManager 管理數據的增刪改查

public class LeDBManager {

    private static Context mContext;
    private LeDBOpenHelper mDbOpenHelper;

    private LeDBManager(Context context) {
        mDbOpenHelper = new LeDBOpenHelper(context);
    }

    private static class SingletonHolder {
        private static final LeDBManager INSTANCE = new LeDBManager(mContext);
    }

    public static final LeDBManager getInstance(Context context) {
        mContext = context;
        return SingletonHolder.INSTANCE;
    }
  //....................

代碼的具體實現如下：

LeDBOpenHelper 類實現

public class LeDBOpenHelper extends SQLiteOpenHelper {

    private static final int DB_VERSION = 1 ;  // 數據庫版本
    private static final String DB_NAME = "leNet.db" ; // 數據庫名稱
    public LeDBOpenHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(createDownloadTable);
    }


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

    }

    public static final String TABLE_DOWNLOAD = "table_download" ;
    public static final String DOWNLOAD_NAME = "download_name" ;
    public static final String DOWNLOAD_URL = "download_url" ;
    public static final String DOWNLOAD_PATH = "download_path" ;
    public static final String DOWNLOAD_TOTAL_SIZE = "download_total_size" ;
    public static final String DOWNLOAD_DOWNLOAD_SIZE = "download_download_size" ;
    public static final String DOWNLOAD_STATUS = "download_status" ;

    private String createDownloadTable = "create table  if not exists table_download (" +
            "id integer primary key autoincrement," +
            "download_name varchar ," +
            "download_url varchar ," +
            "download_path varchar ," +
            "download_total_size long ," +
            "download_download_size long," +
            "download_status smallint" +
            ")" ;


}

LeDBManager 中實現數據的增刪改查

/**
 * Created by familylove on 2017/4/26.
 * 數據庫
 * 增
 * 刪
 * 改
 * 查
 * 管理類
 */

public class LeDBManager {

    private static Context mContext;
    private LeDBOpenHelper mDbOpenHelper;

    private LeDBManager(Context context) {
        mDbOpenHelper = new LeDBOpenHelper(context);
    }

    private static class SingletonHolder {
        private static final LeDBManager INSTANCE = new LeDBManager(mContext);
    }

    public static final LeDBManager getInstance(Context context) {
        mContext = context;
        return SingletonHolder.INSTANCE;
    }

    /**
     * 插入數據
     *
     * @param bean
     */
    public void insertDownload(DownloadBean bean) {
        if (bean == null)
            return;
        SQLiteDatabase db = mDbOpenHelper.getWritableDatabase();
        db.beginTransaction();
        if (!isExistsDownload(db, bean.getUrl())) {
            db.insert(LeDBOpenHelper.TABLE_DOWNLOAD, null, bean.toContentValues(bean));
        }
        db.setTransactionSuccessful();
        db.endTransaction();
        if (db != null)
            db.close();
    }

    /**
     * 刪除數據
     * @param tag
     */
    public boolean deleteDownload(String tag){

        boolean flag = false ;
        if (TextUtils.isEmpty(tag))
            return flag;
        SQLiteDatabase db = mDbOpenHelper.getWritableDatabase() ;
        db.beginTransaction();
        int deleteFlag = db.delete(LeDBOpenHelper.TABLE_DOWNLOAD,LeDBOpenHelper.DOWNLOAD_URL+" = ? ",new String[]{tag}) ;
        db.setTransactionSuccessful();
        db.endTransaction();
        if (db!=null)
            db.close();
        if (deleteFlag==1)
            flag = true ;
        else if (deleteFlag==0)
            flag = false ;
        return flag ;
    }

    /**
     * 更新數據
     *
     * @param tag
     * @param totalSize
     * @param downloadSize
     * @param status
     */
    public void updateDownload(String tag, long totalSize, long downloadSize, int status) {
        SQLiteDatabase db = mDbOpenHelper.getWritableDatabase();
        db.beginTransaction();
        if (isExistsDownload(db, tag)) {
            ContentValues updateCV = new ContentValues();
            updateCV.put(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE, totalSize);
            updateCV.put(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE, downloadSize);
            updateCV.put(LeDBOpenHelper.DOWNLOAD_STATUS, status);
            db.update(LeDBOpenHelper.TABLE_DOWNLOAD, updateCV, LeDBOpenHelper.DOWNLOAD_URL + " = ?", new String[]{tag});
        }
        db.setTransactionSuccessful();
        db.endTransaction();
        if (db != null)
            db.close();
        db = null;
    }

    /**
     * 判斷數據是否存在
     * @param db
     * @param tag
     * @return
     */
    private boolean isExistsDownload(SQLiteDatabase db, String tag) {

        boolean flag = false;
        String sql = "select * from " + LeDBOpenHelper.TABLE_DOWNLOAD + " where " + LeDBOpenHelper.DOWNLOAD_URL + " = ? ";
        Cursor cursor = db.rawQuery(sql, new String[]{tag});

        if (cursor != null && cursor.getCount() > 0) {
            flag = true;
        } else {
            flag = false;
        }
        if (cursor != null)
            cursor.close();
        return flag;
    }

    /**
     * 數據查詢
     * @param tag
     * @return
     */
    public DownloadBean queryOneDownload(String tag) {

        DownloadBean bean = null;
        SQLiteDatabase db = mDbOpenHelper.getReadableDatabase();
        Cursor cursor = db.rawQuery(
                "select * from " + LeDBOpenHelper.TABLE_DOWNLOAD + " where " + LeDBOpenHelper.DOWNLOAD_URL + " = ?",
                new String[]{tag});
        if (cursor != null && cursor.getCount() > 0) {

            if (cursor.moveToNext()) {
                bean = cursorToDownloadBean(cursor);
            }
        }
        if (cursor != null)
            cursor.close();
        if (db != null)
            db.close();
        return bean;
    }

    /**
     * 計算表 tableName 數據總量
     * @param tableName
     * @return 數據表數據總條數
     */
    public int countDownloadBeans(String tableName){

        int count = 0 ;
        SQLiteDatabase db = mDbOpenHelper.getReadableDatabase() ;
        Cursor cursor = db.rawQuery("select count(*) from "+tableName,null) ;
        if (cursor!=null && cursor.getCount()>0){
            cursor.moveToFirst() ;
            count = cursor.getInt(0) ;
        }
        return count ;
    }


    /**
     * cursor to bean
     * @param cursor
     * @return
     */
    private DownloadBean cursorToDownloadBean(Cursor cursor) {
        DownloadBean bean = new DownloadBean();
        bean.setStatus(cursor.getInt(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_STATUS)));
        bean.setDownloadSize(cursor.getLong(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE)));
        bean.setTotalSize(cursor.getLong(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE)));
        bean.setUrl(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_URL)));
        bean.setName(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_NAME)));
        bean.setPath(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_PATH)));
        return bean;
    }

}

DownloadBean類

public class DownloadBean implements Serializable {

    private String name;

    private String path;

    private String url;

    private int status = 0;

    private long totalSize;

    private long downloadSize;

    public long getDownloadSize() {
        return downloadSize;
    }

    public void setDownloadSize(long downloadSize) {
        this.downloadSize = downloadSize;
    }

    public long getTotalSize() {
        return totalSize;
    }

    public void setTotalSize(long totalSize) {
        this.totalSize = totalSize;
    }

    public DownloadBean() {

    }

    public DownloadBean(String name, String path, String url) {
        this.name = name;
        this.path = path;
        this.url = url;
    }


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "DownloadBean{" +
                "name='" + name + '\'' +
                ", path='" + path + '\'' +
                ", url='" + url + '\'' +
                ", status=" + status +
                ", totalSize=" + totalSize +
                ", downloadSize=" + downloadSize +
                '}';
    }

    public ContentValues toContentValues(DownloadBean bean) {

        ContentValues cv = new ContentValues();
        cv.put(LeDBOpenHelper.DOWNLOAD_STATUS, bean.getStatus());
        cv.put(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE, bean.getDownloadSize());
        cv.put(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE, bean.getTotalSize());
        cv.put(LeDBOpenHelper.DOWNLOAD_PATH, bean.getPath());
        cv.put(LeDBOpenHelper.DOWNLOAD_URL, bean.getUrl());
        cv.put(LeDBOpenHelper.DOWNLOAD_NAME, bean.getName());

        return cv;
    }
}

Android Sqlite數據庫增刪改查應用

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Android Sqlite數據庫 增刪改查應用

Android Sqlite數據庫增刪改查應用