首先ActiveAndroid是依靠注解工作的。
@Table(name = "UserBean")
public class UserBean extends Model {
@Column(name = "uid")
public String uid;
@Column(name = "nick_name")
public String nick_name;
public String getUid() {
return uid;
}
public void setUid(String uid) {
this.uid = uid;
}
public String getNick_name() {
return nick_name;
}
public void setNick_name(String nick_name) {
this.nick_name = nick_name;
}
}
对类添加Table注解，对类的成员添加Column注解，因此，我们可以先看看这两个注解的定义。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Table {
public static final String DEFAULT_ID_NAME = "Id";
public String name();
public String id() default DEFAULT_ID_NAME;
}
Table的定义如上，有两个成员，分别是id和name，通常我们只需要设置name，id的名字为设置默认。这个name就是数据库的表名，id为表中作为id字段的名字。
Column的定义比较复杂，但我们可以想象其中一定有name成员，name就是表中的字段名。
然后，ActiveAndroid用了一个TableInfo类保存类和表的连接信息。先来看看这个类
package com.activeandroid;
/*
* Copyright (C) 2010 Michael Pardo
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import android.text.TextUtils;
import android.util.Log;
import com.activeandroid.annotation.Column;
import com.activeandroid.annotation.Table;
import com.activeandroid.util.ReflectionUtils;
public final class TableInfo {
//////////////////////////////////////////////////////////////////////////////////////
// PRIVATE MEMBERS
//////////////////////////////////////////////////////////////////////////////////////
private Class<? extends Model> mType;
private String mTableName;
private String mIdName = Table.DEFAULT_ID_NAME;
private Map<Field, String> mColumnNames = new LinkedHashMap<Field, String>();
//////////////////////////////////////////////////////////////////////////////////////
// CONSTRUCTORS
//////////////////////////////////////////////////////////////////////////////////////
public TableInfo(Class<? extends Model> type) {
mType = type;
final Table tableAnnotation = type.getAnnotation(Table.class);
if (tableAnnotation != null) {
mTableName = tableAnnotation.name();
mIdName = tableAnnotation.id();
}
else {
mTableName = type.getSimpleName();
}
// Manually add the id column since it is not declared like the other columns.
Field idField = getIdField(type);
mColumnNames.put(idField, mIdName);
List<Field> fields = new LinkedList<Field>(ReflectionUtils.getDeclaredColumnFields(type));
Collections.reverse(fields);
for (Field field : fields) {
if (field.isAnnotationPresent(Column.class)) {
final Column columnAnnotation = field.getAnnotation(Column.class);
String columnName = columnAnnotation.name();
if (TextUtils.isEmpty(columnName)) {
columnName = field.getName();
}
mColumnNames.put(field, columnName);
}
}
}
//////////////////////////////////////////////////////////////////////////////////////
// PUBLIC METHODS
//////////////////////////////////////////////////////////////////////////////////////
public Class<? extends Model> getType() {
return mType;
}
public String getTableName() {
return mTableName;
}
public String getIdName() {
return mIdName;
}
public Collection<Field> getFields() {
return mColumnNames.keySet();
}
public String getColumnName(Field field) {
return mColumnNames.get(field);
}
private Field getIdField(Class<?> type) {
if (type.equals(Model.class)) {
try {
return type.getDeclaredField("mId");
}
catch (NoSuchFieldException e) {
Log.e("Impossible!", e.toString());
}
}
else if (type.getSuperclass() != null) {
return getIdField(type.getSuperclass());
}
return null;
}
}
首先是成员变量
private Class<? extends Model> mType;
private String mTableName;
private String mIdName = Table.DEFAULT_ID_NAME;
private Map<Field, String> mColumnNames = new LinkedHashMap<Field, String>();
mType：需要被储存的类的类型;
mTableName：储存的类的表名;
mIdName：储存的类的表的id字段名称;
mColumnNames: 储存的表中的字段名与类中的成员的映射;
public TableInfo(Class<? extends Model> type) {
mType = type;
final Table tableAnnotation = type.getAnnotation(Table.class);
if (tableAnnotation != null) {
mTableName = tableAnnotation.name();
mIdName = tableAnnotation.id();
}
else {
mTableName = type.getSimpleName();
}
......
}
tableAnnotation保存被储存类的注解，并从注解中读出表名和表id名，如果没有注解，则默认类的简名为表名。
public TableInfo(Class<? extends Model> type) {
mType = type;
......
// Manually add the id column since it is not declared like the other columns.
Field idField = getIdField(type);
mColumnNames.put(idField, mIdName);
......
}
手动添加表的id名与类的id关系。看看getIdField方法：
private Field getIdField(Class<?> type) {
if (type.equals(Model.class)) {
try {
return type.getDeclaredField("mId");
}
catch (NoSuchFieldException e) {
Log.e("Impossible!", e.toString());
}
}
else if (type.getSuperclass() != null) {
return getIdField(type.getSuperclass());
}
return null;
}
一个递归，通过getSuperclass()寻找父类，一直到父类为Model，将其中mId成员返回。
public TableInfo(Class<? extends Model> type) {
......
List<Field> fields = new LinkedList<Field>(ReflectionUtils.getDeclaredColumnFields(type));
Collections.reverse(fields);
for (Field field : fields) {
if (field.isAnnotationPresent(Column.class)) {
final Column columnAnnotation = field.getAnnotation(Column.class);
String columnName = columnAnnotation.name();
if (TextUtils.isEmpty(columnName)) {
columnName = field.getName();
}
mColumnNames.put(field, columnName);
}
}
}
如上这段代码，通过反射取出了要储存类的所有标注的成员，并获取它们的注解字段名，如果没有解注字段名，则用成员名代替。最终将它们全部与成员本身一一映射放入mColumnNames中。
以上就是一个TableInfo的初始化过程。下一次将阅读将所有已标注类成员取出的代码。
Done!
时间： 2024-10-11 11:11:58