Java Parcelable类不构成可包裹对象
我试图在捆绑包中保存对象的ArrayList(列表shelfItems),以便在下次打开活动时检索它 (该活动从firestore获取信息,我希望每次打开该活动时减少读取并缩短加载时间) 但我得到了这个错误信息:Java Parcelable类不构成可包裹对象,java,android,arraylist,parcel,Java,Android,Arraylist,Parcel,我试图在捆绑包中保存对象的ArrayList(列表shelfItems),以便在下次打开活动时检索它 (该活动从firestore获取信息,我希望每次打开该活动时减少读取并缩短加载时间) 但我得到了这个错误信息: savedInstanceState.putParcelableArrayList("key", shelfItems); “android.os.Bundle”中的putParcelableArrayList(java.lang.String,java.util.ArrayList
savedInstanceState.putParcelableArrayList("key", shelfItems);
“android.os.Bundle”中的putParcelableArrayList(java.lang.String,java.util.ArrayList)“不能应用于”(java.lang.String,java.util.List)”
这是我的对象类:
import android.os.Parcel;
import android.os.Parcelable;
public class ShelfItem implements Parcelable{
private String mTitle;
private String mAuthor;
private String mThumbnail;
private long mRating;
private long mEndDate;
private long mBeginDate;
private String mId;
private long mPages;
private boolean mVisible;
//make ShelfItem object
public ShelfItem(String title, String author, String thumbnail, long rating, long beginDate, long endDate, String id, long pages, boolean visible) {
mTitle = title;
mAuthor = author;
mThumbnail = thumbnail;
mRating = rating;
mBeginDate = beginDate;
mEndDate = endDate;
mId = id;
mPages = pages;
mVisible = visible;
}
public String getTitle() {
return mTitle;
}
public String getAuthor() {
return mAuthor;
}
public String getThumbnail() {
return mThumbnail;
}
public long getRating() {
return mRating;
}
public long getBeginDate() {
return mBeginDate;
}
public long getEndDate() {
return mEndDate;
}
public String getId() {
return mId;
}
public long getPages() {
return mPages;
}
public boolean getVisible() {
return mVisible;
}
public ShelfItem(Parcel in) {
mId = in.readString();
mTitle = in.readString();
mAuthor = in.readString();
mThumbnail = in.readString();
mBeginDate = in.readLong();
mEndDate = in.readLong();
mPages = in.readLong();
mVisible = in.readByte() != 0;
mRating = in.readLong();
}
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel out, int flags) {
out.writeString(mId);
out.writeString(mTitle);
out.writeString(mAuthor);
out.writeString(mThumbnail);
out.writeLong(mBeginDate);
out.writeLong(mEndDate);
out.writeLong(mPages);
out.writeByte((byte) (mVisible ? 1 : 0));
out.writeLong(mRating);
}
public static final Parcelable.Creator<ShelfItem> CREATOR = new Parcelable.Creator<ShelfItem>() {
public ShelfItem createFromParcel(Parcel in) {
return new ShelfItem(in);
}
public ShelfItem[] newArray(int size) {
return new ShelfItem[size];
}
};
}
在学习Java时,我们被教导在声明变量时使用接口类型(
List
),而不是实现类型(ArrayList
)。您可能有这样的代码:
List<ShelfItem> shelfItems = new ArrayList<>();
如果您从其他地方获取列表,并且无法控制列表的实现类型,则可以在需要保存时构造一个新的ArrayList
:
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
ArrayList<ShelfItem> toSave = new ArrayList<>(shelfItems);
savedInstanceState.putParcelableArrayList("key", toSave);
}
@覆盖
SaveInstanceState上的公共无效(Bundle savedInstanceState){
super.onSaveInstanceState(savedInstanceState);
ArrayList toSave=新的ArrayList(shelfItems);
savedInstanceState.putParcelableArrayList(“key”,toSave);
}
ArrayList<ShelfItem> shelfItems = new ArrayList<>();
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
ArrayList<ShelfItem> toSave = new ArrayList<>(shelfItems);
savedInstanceState.putParcelableArrayList("key", toSave);
}