android OrmLite 实际应用
相信看了上一篇 ormLite 入门，对ormLite框架也有了个基本的认识
今天我们来了解一下ormLite的实际应用
现在我们有2张表，分为是t_student，t_class，我们学生表中有班级外键的引用
我们来看一下代码:
1.首先是实体类
学生表:
@DatabaseTable(tableName = Student.TABLE_NAME)public class Student { public final static String TABLE_NAME = "t_student"; @DatabaseField(generatedId = true) private int id; @DatabaseField(defaultValue = "小明") private String name; @DatabaseField(foreign = true,columnName = "ofClss",foreignAutoRefresh = true) private Classz ofClass;}
我们的外键引用的是一个Classz的类型
班级表:
@DatabaseTable(tableName = Classz.TABLE_NAME)public class Classz { public final static String TABLE_NAME = "t_class"; @DatabaseField(id = true) private String id; @DatabaseField(unique = true,canBeNull = false) private String name; @DatabaseField(defaultValue = "工科楼") private String address;}
2.helper类
public class DatabaseHelper extends OrmLiteSqliteOpenHelper { private static final String TABLE_NAME = "my_orm_db"; private static final int VERSION = 1; private static DatabaseHelper instance; public static DatabaseHelper getInstance(Context mContext) { mContext = mContext.getApplicationContext(); if (instance == null) { synchronized (DatabaseHelper.class) { if (instance == null) { instance = new DatabaseHelper(mContext); } } } return instance; } public DatabaseHelper(Context context) { super(context, TABLE_NAME, null, VERSION); } @Override public void onCreate(SQLiteDatabase sqLiteDatabase, ConnectionSource connectionSource) { Log.d("myorm", "表开始新建"); try { TableUtils.createTable(connectionSource, Student.class); TableUtils.createTable(connectionSource, Classz.class); Log.d("MyOrm", "表创建成功"); } catch (SQLException e) { Log.d("MyOrm", "表创建失败"); e.printStackTrace(); } } @Override public void onUpgrade(SQLiteDatabase sqLiteDatabase, ConnectionSource connectionSource, int oldV, int newV) { Log.d("MyOrm", "更新表: old:" + oldV + " newV" + newV); } /** * * @param db * @param tableName 要修改的表 * @param columnName 要添加的字段 * @param columnType 字段类型 * @param defaultField 默认值 */ public synchronized void updateColumn(SQLiteDatabase db, String tableName, String columnName, String columnType, Object defaultField) { try { if (db != null) { Cursor c = db.rawQuery("SELECT * from " + tableName + " limit 1 ", null); boolean flag = false; if (c != null) { for (int i = 0; i < c.getColumnCount(); i++) { if (columnName.equalsIgnoreCase(c.getColumnName(i))) { flag = true; break; } } if (flag == false) { String sql = "alter table " + tableName + " add " + columnName + " " + columnType + " default " + defaultField; db.execSQL(sql); } c.close(); } } } catch (Exception e) { Log.d("MyOrm", "更新失败"); e.printStackTrace(); } }}
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helper类中，我们添加了一个updateColumn方法，用来修改表结构，而不在是不负责任的直接删除了
3.我们的Dao类
因为有多个Dao类 所以我们写一个BaseDao类，集成了基本的CRUD操作
public abstract class BaseDao<T,ID> { private DatabaseHelper helper; public BaseDao(Context context) { helper = DatabaseHelper.getInstance(context); } public DatabaseHelper getHelper() { return helper; } public abstract Dao<T, ID> getDao(); public int add(T t){ try { return getDao().create(t); } catch (SQLException e) { e.printStackTrace(); } return -1; } public int addList(List<T> list){ try { return getDao().create(list); } catch (SQLException e) { e.printStackTrace(); } return -1; } public List<T> getAll(){ List<T> list = new ArrayList<>(); try { list = getDao().queryForAll(); } catch (SQLException e) { e.printStackTrace(); } return list; } public T get(ID id){ try { return getDao().queryForId(id); } catch (SQLException e) { e.printStackTrace(); } return null; } public int update(T t){ try { return getDao().update(t); } catch (SQLException e) { e.printStackTrace(); } return -1; } public int delete(ID id){ try { return getDao().deleteById(id); } catch (SQLException e) { e.printStackTrace(); } return -1; }}
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接着是我们的StudentDao
public class StudentDao extends BaseDao<Student,Integer> { public StudentDao(Context context) { super(context); } @Override public Dao<Student,Integer> getDao() { try { return getHelper().getDao(Student.class); } catch (SQLException e) { e.printStackTrace(); } return null; }}
ClasszDao类
public class ClasszDao extends BaseDao<Classz, String> { public ClasszDao(Context context) { super(context); } @Override public Dao<Classz, String> getDao() { try { return getHelper().getDao(Classz.class); } catch (SQLException e) { e.printStackTrace(); } return null; } /** * 根据班级名称获取班级信息 * @param className * @return */ public Classz getClassz(String className){ try { List<Classz> name = getDao().queryBuilder() .where().eq("name", className) .query(); if(name!=null && name.size() >0){ return name.get(0); } } catch (SQLException e) { e.printStackTrace(); } return null; }}
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我们的实现类中重写getDao方法，返回有相应泛型约束的Dao.
4.我们的MainActivity
public class MainActivity extends AppCompatActivity { private StudentDao studentDao; private ClasszDao classzDao; private EditText edittxt; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); studentDao = new StudentDao(this); classzDao = new ClasszDao(this); edittxt = (EditText) findViewById(R.id.edittxt); } int i = 1; public void c(View view){ Classz classz = new Classz(); classz.setId(System.currentTimeMillis()+""); classz.setName("计算机科学与技术"+i+"班"); Student student = new Student(); student.setOfClass(classz); student.setName("小明"+i); i++; int add = studentDao.add(student); Log.d("MyOrm",add>-1?"student 插入成功: "+add:"student 插入失败"); int add1 = classzDao.add(classz); Log.d("MyOrm",add1>-1?"classz 插入成功: "+add1:"classz 插入失败"); } public void r(View view){ String s = edittxt.getText().toString(); try{ int i = Integer.parseInt(s); Student student = studentDao.get(i); Log.d("MyOrm",student.toString()); }catch (NumberFormatException e){ e.printStackTrace(); } } public void r_all(View view){ List<Student> all = studentDao.getAll(); List<Classz> all1 = classzDao.getAll(); Log.d("MyOrm",all.toString()+"---classz: "+all1.toString()); } public void u(View view){ Student student = studentDao.get(3); Classz classz = classzDao.getClassz("计算机科学与技术1班"); student.setOfClass(classz); int update = studentDao.update(student); Log.d("MyOrm",update>-1?"转班成功: "+update:"转班失败"); } public void d(View view){ String s = edittxt.getText().toString(); try{ int i = Integer.parseInt(s); int result = studentDao.delete(i); Log.d("MyOrm",result>-1?"删除成功: "+result:"删除失败"); }catch (NumberFormatException e){ e.printStackTrace(); } }}
