我正在我的 Android 应用程序中实现 ActiveAndroid,为此我指的是 this link .我的问题定义是,我在改造库的帮助下从服务器获取数据列表。获取数据列表后,我将数据插入到我的“ActiveAndroid”数据库中。在调试我的应用程序时,我检查了模型类的外键和其他数据成员的数据是否正确,但是当我尝试从“ActiveAndroid”取回数据时我得到的外键为空。我用谷歌搜索了很多但仍无法追踪问题。有关更多信息,请查看以下详细信息--
目前我有以下模型类—— 1]Event.java类
@Table(name = "Events")
public class Event extends Model
{
@Column(name = "eventID")
private int eventID;
@Column(name = "eventName")
private String eventName;
@Column(name = "Ground")
private Ground ground;
public Event() {
super();
// TODO Auto-generated constructor stub
}
public Event(int eventID, String eventName,
Ground ground) {
super();
this.eventID = eventID;
this.eventName = eventName;
this.ground = ground;
}
public int getEventID() {
return eventID;
}
public void setEventID(int eventID) {
this.eventID = eventID;
}
public String getEventName() {
return eventName;
}
public void setEventName(String eventName) {
this.eventName = eventName;
}
public Ground getGround() {
return ground;
}
public void setGround(Ground ground) {
this.ground = ground;
}
}
如上“Event”模型类所示,有一个外键,即“Ground”。
2] Ground.java类是--
Table(name = "Ground")
public class Ground extends Model
{
@Column(name = "groundID")
private int groundID;
@Column(name = "groundName")
private String groundName;
public Ground() {
super();
// TODO Auto-generated constructor stub
}
public int getGroundID() {
return groundID;
}
public void setGroundID(int groundID) {
this.groundID = groundID;
}
public String getGroundName() {
return groundName;
}
public void setGroundName(String groundName) {
this.groundName = groundName;
}
public Ground(int groundID, String groundName)
{
super();
this.groundID = groundID;
this.groundName = groundName;
}
}
3] 这就是我在“ActiveAndroid DB”中存储事件的方式
ActiveAndroid.beginTransaction();
try
{
for (int i = 0; i < list.size(); i++)
{
list.get(i).save();
/*
Also tried---
list.get(i).getGround.save();
list.get(i).save();
*/
}
ActiveAndroid.setTransactionSuccessful();
}
finally
{
ActiveAndroid.endTransaction();
}
4] 这就是我从“ActiveAndroid”数据库获取事件列表的方式
public static List<Event> getAllEvents()
{
return new Select()
.all()
.from(Event.class)
.execute();
}
但是从“ActiveAndroid”获取列表后,我将“Ground”字段设为空。请指导我哪里出错了,如果我能提供更多信息,请告诉我这样你就可以很容易地理解我的问题。谢谢!
最佳答案
请尝试下面的代码,它可能对您有帮助。
@Table(name = "Events")
public class Event extends Model {
@Column(name = "eventID")
private int eventID;
@Column(name = "eventName")
private String eventName;
@Column(name = "Ground", onUpdate = Column.ForeignKeyAction.CASCADE, onDelete = Column.ForeignKeyAction.CASCADE)
private Ground ground;
public Event() {
super();
// TODO Auto-generated constructor stub
}
public Event(int eventID, String eventName,
Ground ground) {
super();
this.eventID = eventID;
this.eventName = eventName;
this.ground = ground;
}
public int getEventID() {
return eventID;
}
public void setEventID(int eventID) {
this.eventID = eventID;
}
public String getEventName() {
return eventName;
}
public void setEventName(String eventName) {
this.eventName = eventName;
}
public Ground getGround() {
return getMany(Ground.class, "Ground");//or/*new Select().from(Ground.class).execute();*/
}
public void setGround(Ground ground) {
this.ground = ground;
}
}
关于android - 在 ActiveAndroid 中获取外键成员 "null",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40837867/