Android 数据库操作 创建 添加 删除 查询

第一步创建数据库工具类：

import java.util.ArrayList;  import java.util.List;    import android.content.ContentValues;  import android.content.Context;  import android.database.Cursor;  import android.database.sqlite.SQLiteDatabase;  import android.database.sqlite.SQLiteOpenHelper;    public class DBHelper {        DBConnection helper;        public DBHelper(Context ctx) {          helper = new DBConnection(ctx);      }        public DBHelper() {      }        public void add(ContentValues values) {            SQLiteDatabase db = helper.getWritableDatabase();          db.insert(UserSchema.TABLE_NAME, null, values);          db.close();        }        public void DropTable(String TB_NAME) {          try {                SQLiteDatabase db = helper.getWritableDatabase();              String sql = "DROP TABLE " + TB_NAME;              db.execSQL(sql);          } catch (Exception ex) {            }      }        public void DropDatabase(Context ctx, String DATABASE_NAME) {          try {              ctx.deleteDatabase(DATABASE_NAME);          } catch (Exception ex) {            }      }        public void update(ContentValues values, String where, String[] whereArgs) {            SQLiteDatabase db = helper.getWritableDatabase();          db.update(UserSchema.TABLE_NAME, values, where, whereArgs);          db.close();      }        public void delete(String where, String[] whereArgs) {            SQLiteDatabase db = helper.getWritableDatabase();          db.delete(UserSchema.TABLE_NAME, where, whereArgs);          db.close();      }        public void delDB(String DBName) {            SQLiteDatabase db = helper.getWritableDatabase();          db.execSQL("DROP Database " + DBName);          db.close();      }        public List query(String where, String[] whereArgs, String orderBy,              String limit) {            try {              final SQLiteDatabase db = helper.getReadableDatabase();              Cursor c = null;              c = db.query(UserSchema.TABLE_NAME, null, where, whereArgs, null,                      null, orderBy, limit);              List lst = new ArrayList();                while (c != null && c.moveToNext()) {                  CItem item = new CItem();                  item.setID(c.getString(c.getColumnIndex("m_key")));                  item.setValue(c.getString(c.getColumnIndex("m_value")));                  lst.add(item);              }              if (c != null)c.close();              return lst;          } catch (Exception e) {              // TODO: handle exception          }            return null;        }        public interface UserSchema {            String TABLE_NAME = "movement";          String ID = "m_id";          String TYPE = "m_type";          String Key = "m_key";          String Value = "m_value";        }        public static class DBConnection extends SQLiteOpenHelper {          private static final String DATABASE_NAME = "SP.db";          private static final int DATABASE_VERSION = 1;            private DBConnection(Context ctx) {              super(ctx, DATABASE_NAME, null, DATABASE_VERSION);          }            @Override          public void onCreate(SQLiteDatabase db) {                String create_sql = "CREATE TABLE movement(m_id integer primary key autoincrement,m_type varchar(10),"                      + "m_key varchar(20),m_value varchar(100),m_order integer)";              db.execSQL(create_sql);          }            @Override          public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {              // TODO Auto-generated method stub              // String alter_sql = "ALTER TABLE movement";              // db.execSQL(alter_sql);            }        }    }    使用数据库如下代码：  public DBHelper getDb() {          if (db == null)              db = new DBHelper(this);          return db;      }    添加：    ContentValues cv = new ContentValues();              cv.put("m_type", type);              cv.put("m_key", key);              cv.put("m_value", value);              getDb().add(cv);    查询：    List lst = getDb().query("m_type=?", new String[] { cmd }, null, null);