我想跟踪谁创建了一个实体，以及谁编辑（最后）该实体。因为我想为我的项目中的每个实体执行此操作，所以我在名为EntityBase的基类中执行此操作。
如果我使用相应的ForeignKey属性取消注释EntityBase类中的EditorUser，则Context.Database.EnsureCreated方法将引发以下异常：
InvalidOperationException异常： 附加信息：无法确定在“User.CreatorUser”和“User”之间检测到的一对一关系的子/从属方。要标识关系的子/依赖方，请配置外键属性。
任何人都可以帮我配置模型以满足我的要求吗？
public class EntityBase
{
public Guid Id { get; set; }
public Guid CreatorUserId { get; set; }
[ForeignKey(nameof(CreatorUserId))]
public User CreatorUser { get; set; }
public Guid? EditorUserId { get; set; }
//[ForeignKey(nameof(EditorUserId))]
//public User EditorUser { get; set; }
}
public class User : EntityBase
{
public String Name { get; set; }
}
public class House : EntityBase
{
public String Address { get; set; }
}
class Context : DbContext
{
public Guid CurrentUserId = new Guid("3de85c1f-3ce1-4342-a582-83d6cc8e308f");
public DbSet<User> Users { get; set; }
public DbSet<House> Houses { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlite(@"Data Source = c:\Temp\eftest.db;");
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
foreach (var relationship in modelBuilder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
{
relationship.DeleteBehavior = DeleteBehavior.Restrict;
}
base.OnModelCreating(modelBuilder);
}
public override int SaveChanges()
{
var changeSet = ChangeTracker.Entries<EntityBase>();
if (changeSet != null)
{
foreach (var entry in changeSet.Where(c => c.State != EntityState.Unchanged))
{
switch (entry.State)
{
case EntityState.Added:
entry.Entity.CreatorUserId = CurrentUserId;
break;
default:
entry.Entity.EditorUserId = CurrentUserId;
break;
}
}
}
return base.SaveChanges();
}
}
答案 0 :(得分：1)
好吧，基本上CreatorUser EntityBase User来自EntityBase，EntityBase为public class CenteringHorizontalScrollView extends HorizontalScrollView implements View.OnTouchListener {
private static final int SWIPE_PAGE_ON_FACTOR = 5;
View targetLeft, targetRight;
CircleImageView leftImage, rightImage;
private Context mContext;
private int mActiveItem;
private float mPrevScrollX;
private int mItemWidth = 250;// or whatever your item width is.
private int centreItemWidth = 350;
private final int LEFT = 1;
private final int RIGHT = 2;
private final int NA = 0;
private final int emptyView = 2;
private static String TAG = CenteringHorizontalScrollView.class.getSimpleName();
public CenteringHorizontalScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
setOnTouchListener(this);
}
@Override
public boolean onTouch(View v, MotionEvent event) {
int x = (int) event.getRawX();
boolean handled = false;
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mPrevScrollX = x;
break;
case MotionEvent.ACTION_MOVE:
break;
case MotionEvent.ACTION_UP:
int minFactor = mItemWidth / SWIPE_PAGE_ON_FACTOR;
if ((mPrevScrollX - (float) x) > minFactor) {
if (mActiveItem < getMaxItemCount() - 1 - emptyView) {
setCurrentItem(mActiveItem + 1);
CommonConstant.currentChildIdx = (mActiveItem - emptyView);
}
} else if (((float) x - mPrevScrollX) > minFactor) {
if (mActiveItem > 0 + emptyView) {
setCurrentItem(mActiveItem - 1);
CommonConstant.currentChildIdx = (mActiveItem - emptyView);
}
}
scrollToActiveItem(NA);
handled = true;
break;
}
return handled;
}
private int getMaxItemCount() {
return ((LinearLayout) getChildAt(0)).getChildCount();
}
private LinearLayout getLinearLayout() {
return (LinearLayout) getChildAt(0);
}
private void setCurrentItem(int cur) {
if (cur < 0 + emptyView) {
mActiveItem = 2;
} else if (cur > getMaxItemCount() - 1 - emptyView) {
mActiveItem = getMaxItemCount() - 1 - emptyView;
} else {
mActiveItem = cur;
}
}
/**
* Scrolls the list view to the currently active child.
*/
private void scrollToActiveItem(int direction) {
int maxItemCount = getMaxItemCount();
if (maxItemCount == 0) {
return;
}
int targetItem = Math.min(maxItemCount - 1, mActiveItem);
targetItem = Math.max(0, targetItem);
setCurrentItem(targetItem);
targetItem = mActiveItem;
// Scroll so that the target child is centered
View targetView = getLinearLayout().getChildAt(targetItem);
LinearLayout centerLayout = (LinearLayout) targetView;
ImageView centerImage = (ImageView) centerLayout.getChildAt(0);
centerImage.setBackground(mContext.getResources().getDrawable(R.drawable.rectangle_background));
//get the image to left of the centered image
if ((targetItem - 1) >= 0) {
targetLeft = getLinearLayout().getChildAt(targetItem - 1);
LinearLayout ll = (LinearLayout) targetLeft;
leftImage = (CircleImageView) ll.getChildAt(0);
centerImage.setBackground(null);
}
//get the image to right of the centered image
if ((targetItem + 1) < maxItemCount) {
targetRight = getLinearLayout().getChildAt(targetItem + 1);
LinearLayout ll = (LinearLayout) targetRight;
rightImage = (CircleImageView) ll.getChildAt(0);
centerImage.setBackground(null);
}
int targetLeftx = centerLayout.getLeft();
int childWidth = centerLayout.getRight() - targetLeftx;
int width = getWidth() - getPaddingLeft() - getPaddingRight();
int targetScroll = targetLeftx - ((width - childWidth) / 2);
super.smoothScrollTo(targetScroll, 0);
}
/**
* Sets the current item and centers it.
*
* @param currentItem The new current item.
*/
public void setCurrentItemAndCenter(int currentItem) {
setCurrentItem(currentItem + emptyView);
scrollToActiveItem(NA);
}
}
。所以它有点像鸡与蛋的问题。
您可以为Parent创建另一个用户实体，并将其添加到 private void initScrollView() {
tools_top_scroll = (CenteringHorizontalScrollView) getActivity().findViewById(R.id.horizontalScrollView);
rl = (LinearLayout) getActivity().findViewById(R.id.tools_top);
addEmptyChildView();
addEmptyChildView();
for (int i = 0; i < 5; i++) {
setInnerChildView(getChildren().get(i));
}
addEmptyChildView();
addEmptyChildView();
tools_top_scroll.post(new Runnable()
{
@Override
public void run()
{
tools_top_scroll.setCurrentItemAndCenter(CommonConstant.currentChildIdx);
}
});
}
private void setInnerChildView(ChildR childR) {
View view = LayoutInflater.from(getActivity()).inflate(R.layout.item_head_name, null);
ImageView child_img = (ImageView) view.findViewById(R.id.child_img);
TextView child_name = (TextView) view.findViewById(R.id.child_name);
Log.i(TAG, "child name:" + childR.getChild().getC_name());
child_name.setText(childR.getChild().getC_name());
rl.addView(view);
}
private void addEmptyChildView() {
View view = LayoutInflater.from(getActivity()).inflate(R.layout.item_head_name, null);
view.setVisibility(View.INVISIBLE);
rl.addView(view);
}
。