1、我們接著上一篇文章講，實(shí)現(xiàn)數(shù)據(jù)庫框架的刪改查的功能，建議先看上篇文章后再看這篇文章，文章地址：Android手寫數(shù)據(jù)庫框架設(shè)計(jì)（增）。
我們插入數(shù)據(jù)庫的操作在BaseDao里面完成的，具體的插入代碼：
@Override
public Long insert(T entity) {
Map<String, String> map = getValues(entity);
ContentValues contentValues = getContentValues(map);
Long result = mDatabase.insert(tableName, null, contentValues);
return result;
}
2、在IBaseDao接口中，我們?cè)黾觿h改查的方法。
public interface IBaseDao<T> {
//插入數(shù)據(jù)
Long insert(T t);
//更新數(shù)據(jù)
int update(T entity,T where);1
//刪除數(shù)據(jù)
int delete(T where);2
//查詢數(shù)據(jù)
List<T> query(T where);3
List<T> query(T where,String orderBy,Integer startIndex,Integer limit);4
List<T> query(String sql);5
}
更新數(shù)據(jù)的方法1處代碼傳入兩個(gè)參數(shù)，entity是要跟改的實(shí)體類，where是，2,3,4,5處的代碼就不做過多的解讀了。
BaseDao中刪改查的方法：
@Override
public int update(T entity, T where) {
int result = -1;
Map values = getValues(entity);
/**
* 將條件對(duì)象轉(zhuǎn)化為map
*/
Map whereClause = getValues(where);
Condition condition = new Condition(whereClause);
ContentValues contentValues = getContentValues(values);
result = mDatabase.update(tableName, contentValues,condition.getWhereClause(), condition.getWhereArgs());
return result;
}
@Override
public int delete(T where) {
Map map = getValues(where);
Condition condition = new Condition(map);
/**
* id=1 數(shù)據(jù)
* id=? new String[]{String.value(1)}
*/
int result = mDatabase.delete(tableName,condition.getWhereClause(),condition.getWhereArgs());
return result;
}
@Override
public List<T> query(T where) {
return query(where, null, null, null);
}
@Override
public List<T> query(T where, String orderBy, Integer startIndex, Integer limit) {
Map map = getValues(where);
String limitString = null;
if (startIndex != null && limit != null) {
limitString = startIndex + " , " + limit;
}
Condition condition = new Condition(map);
/**
* public Cursor query(String table, String[] columns, String selection,
String[] selectionArgs, String groupBy, String having,
String orderBy, String limit)
*/
Cursor cursor = mDatabase.query(tableName, null, condition.getWhereClause(), condition.getWhereArgs(), null, null, orderBy, limitString);
List<T> result = getResult(cursor, where);
return result;
}
在這里我們重點(diǎn)關(guān)注Condition類和getRelsult(cursor, where)方法，Condition類里面的代碼：
/**
* 封裝修改語句
*/
class Condition {
/**
* 查詢條件 "name=?&&password=?"
*/
private String whereClause;
private String[] whereArgs;
/**
* sqliteDatabase.update(tableName, contentValues, whereClause, whereArgs);
* sqliteDatabase.delete(tableName, whereClause, whereArgs);
*/
public Condition(Map<String, String> whereClause) {
ArrayList list = new ArrayList();
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append(" 1=1 ");
Set keys = whereClause.keySet();
Iterator iterator = keys.iterator();
while (iterator.hasNext()) {
String key = (String) iterator.next();
String value = whereClause.get(key);
if (value != null) {
/*
拼接條件查詢語句
1=1 and name =? and password=?
*/
stringBuilder.append(" and " + key + " =?");
list.add(value);
}
}
this.whereClause = stringBuilder.toString();
this.whereArgs = (String[]) list.toArray(new String[list.size()]);
}
public String getWhereClause() {
return whereClause;
}
public String[] getWhereArgs() {
return whereArgs;
}
}
Condition的作用主要是Map轉(zhuǎn)換為修改數(shù)據(jù)庫和查詢數(shù)據(jù)庫的條件字符串和給條件語句等號(hào)后的變量賦值的String數(shù)組。
getRelsult(cursor, where)的代碼：
private List<T> getResult(Cursor cursor, T where) {
ArrayList list = new ArrayList();
Object item;
while (cursor.moveToNext()) {
try {
item = where.getClass().newInstance();
/**
* 列名 name
* 成員變量名 Filed;
*/
Iterator iterator = cacheMap.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = (Map.Entry) iterator.next();
//得到列名
String columName = (String) entry.getKey();
//然后以列名拿到列名在游標(biāo)的位置
int columnIndex = cursor.getColumnIndex(columName);
//拿到cacheMap里面key對(duì)應(yīng)的field
Field field = (Field) entry.getValue();
//拿到成員變量的類型
Class type = field.getType();
if (columnIndex != -1) {
if (type == String.class) {
//反射方式賦值
field.set(item, cursor.getString(columnIndex));
} else if (type == Double.class) {
field.set(item, cursor.getDouble(columnIndex));
} else if (type == Long.class) {
field.set(item, cursor.getLong(columnIndex));
} else if (type == Integer.class) {
field.set(item,cursor.getInt(columnIndex));
}else if (type == byte[].class){
field.set(item,cursor.getBlob(columnIndex));
}else {
//不支持的類型
continue;
}
}
}
list.add(item);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
return list;
}
這個(gè)方法主要是對(duì)查詢的游標(biāo)cursor操作，通過傳進(jìn)來的where實(shí)例化對(duì)象，賦值后添加到集合，返回。
調(diào)用端的代碼：
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
IBaseDao<User> userDao;
// IBaseDao<DownFile> downDao;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
userDao = BaseDaoFactory.getInstance().getDataHelper(UserDao.class, User.class);
// downDao = BaseDaoFactory.getInstance().getDataHelper(DownDao.class, DownFile.class);
}
public void save(View view) {
for (int i = 0; i < 4; i++) {
User user = new User("lcty", "123456");
userDao.insert(user);
}
}
public void delete(View view) {
User user = new User();
user.setName("haha");
userDao.delete(user);
}
public void queryList(View view) {
User where = new User();
where.setName("haha");
List<User> list = userDao.query(where);
Log.i(TAG, "查詢到 " + list.size() + " 條數(shù)據(jù)");
}
public void update(View view) {
User where = new User();
where.setName("lcty");
User user = new User("haha", "123456789");
userDao.update(user, where);
}
}
效果我就不貼了，感興趣的伙伴可以自己敲一遍看下效果，分析完畢，歡迎交流。
