数据库的创建以及对数据库的增删改查

数据库的创建以及对数据库的增删改查

'''public class NewsSQLiteOpenHelper extends SQLiteOpenHelper{
private static final String  DB_NAME = "NEWS.DB";//数据库名称
private static final int DB_VERSION = 4;//数据库版本号
public NewsSQLiteOpenHelper(Context context){
super(context,DB_NAME,null,DB_VERSION);
}
//version  数据库版本号 context 上下文 name数据库名字
public NewsSQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
public NewsSQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler) {
super(context, name, factory, version, errorHandler);
}
@Override
public void **onCreate**(SQLiteDatabase db) {
//获取创建表格的SQL
String netNewsSQL =Constant.NewNewsTable.getCreatNetNewsSQL();
//Z执行SQL
db.execSQL(netNewsSQL);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table "+ Constant.NewNewsTable.TBL_NAME);
onCreate(db);
}

public static final class NewNewsTable {
public static final String TBL_NAME = "NETNEWS";
public static final String COL_ID = "ID";
public static final String COL_TITLE = "TITLE";
public static final String COL_CTIME = "CTIME";
public static final String COL_PICURL = "PICURL";
public static final String COL_URL = "URL";
public static final String COL_DESCRIPTION = "DESCRIPTION";
public static final String COL_NEWSTYPE = "NEWSTYPE";

public static String getCreatNetNewsSQL() {
String sql = "CREATE TABLE IF NOT EXISTS "
+ TBL_NAME + "(" + COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
+ COL_TITLE + " VARCHAR(200),"
+ COL_CTIME + " VARCHAR(50),"
+ COL_PICURL + " VARCHAR(200),"
+ COL_URL + " VARCHAR(200),"
+ COL_DESCRIPTION + " TEXT,"
+ COL_NEWSTYPE + " integer"
+ ")";
return sql;
}'

public class NetNewsDao  {
private NewsSQLiteOpenHelper openHelper;
public NetNewsDao(Context mContext){
this.openHelper = new NewsSQLiteOpenHelper(mContext);
}
public List<NetNews> findNewsByType(int type){
List<NetNews> list = new ArrayList<>();
SQLiteDatabase db = this.openHelper.getReadableDatabase();
Cursor cursor = db.query(
Constant.NewNewsTable.TBL_NAME,
new String[]{
Constant.NewNewsTable.COL_ID,
Constant.NewNewsTable.COL_CTIME,
Constant.NewNewsTable.COL_DESCRIPTION,
Constant.NewNewsTable.COL_TITLE,
Constant.NewNewsTable.COL_PICURL,
Constant.NewNewsTable.COL_URL,
Constant.NewNewsTable.COL_NEWSTYPE
},
Constant.NewNewsTable.COL_NEWSTYPE+" =?",
new String[]{type+""},
null,
null,
null,
null
);
while(cursor.moveToNext()){
NetNews nn = new NetNews();
nn.setTitle(cursor.getString(cursor.getColumnIndex(Constant.NewNewsTable.COL_TITLE)));
nn.setCtime(cursor.getString(cursor.getColumnIndex(Constant.NewNewsTable.COL_CTIME)));
nn.setDescription(cursor.getString(cursor.getColumnIndex(Constant.NewNewsTable.COL_DESCRIPTION)));
nn.setPicUrl(cursor.getString(cursor.getColumnIndex(Constant.NewNewsTable.COL_PICURL)));
nn.setUrl(cursor.getString(cursor.getColumnIndex(Constant.NewNewsTable.COL_URL)));
nn.setNewsType(cursor.getInt(cursor.getColumnIndex(Constant.NewNewsTable.COL_NEWSTYPE)));
list.add(nn);
}
cursor.close();
db.close();
return list;
}
public long addNetNews(NetNews nn){
SQLiteDatabase db = this.openHelper.getReadableDatabase();
ContentValues values = new ContentValues();
values.put(Constant.NewNewsTable.COL_TITLE,nn.getTitle());
values.put(Constant.NewNewsTable.COL_DESCRIPTION,nn.getDescription());
values.put(Constant.NewNewsTable.COL_CTIME,nn.getCtime());
values.put(Constant.NewNewsTable.COL_PICURL,nn.getPicUrl());
values.put(Constant.NewNewsTable.COL_URL,nn.getPicUrl());
values.put(Constant.NewNewsTable.COL_NEWSTYPE, nn.getNewsType());
long id = db.insert(
Constant.NewNewsTable.TBL_NAME,
null,
values
);
db.close();
return id;
}
public  void addNetNews(List<NetNews> netNewsList){
for(NetNews nn:netNewsList){
addNetNews(nn);
}
}
public void removeNewsByType(int type){
SQLiteDatabase DB = this.openHelper.getReadableDatabase();
//根据新闻类型删除
DB.delete(
Constant.NewNewsTable.TBL_NAME,
Constant.NewNewsTable.COL_NEWSTYPE+" =?",
new String[]{type+""}
);
DB.close();
}