Java 使用parcelable 将项目存储为共享首选项？
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Use parcelable to store item as sharedpreferences?
提问by xsiand
I have a couple objects, Location, in my app stored in an ArrayList and use parcelable to move these between activities. The code for the object looks like this:
我的应用程序中有几个对象 Location，存储在 ArrayList 中，并使用 Parcelable 在活动之间移动这些对象。该对象的代码如下所示：
public class Location implements Parcelable{
private double latitude, longitude;
private int sensors = 1;
private boolean day;
private int cloudiness;
/*
M?ste ha samma ordning som writeToParcel f?r att kunna ?terskapa objektet.
*/
public Location(Parcel in){
this.latitude = in.readDouble();
this.longitude = in.readDouble();
this.sensors = in.readInt();
}
public Location(double latitude, double longitude){
super();
this.latitude = latitude;
this.longitude = longitude;
}
public void addSensors(){
sensors++;
}
public void addSensors(int i){
sensors = sensors + i;
}
+ Some getters and setters.
Now I am in need of storing these objects more permanently. I read somewhere that I can serialize the objects and save as sharedPreferences. Do I have to implement serializeable aswell or can I do something similar with parcelable?
现在我需要更永久地存储这些对象。我在某处读到我可以序列化对象并保存为共享首选项。我是否还必须实现可序列化，或者我可以用 Parcelable 做类似的事情吗？
采纳答案by StenSoft
From documentation of Parcel:
来自Parcel 的文档：
Parcel is not a general-purpose serialization mechanism. This class (and the corresponding Parcelable API for placing arbitrary objects into a Parcel) is designed as a high-performance IPC transport. As such, it is not appropriate to place any Parcel data in to persistent storage: changes in the underlying implementation of any of the data in the Parcel can render older data unreadable.
Parcel 不是通用的序列化机制。此类（以及用于将任意对象放入 Parcel 的相应 Parcelable API）被设计为高性能 IPC 传输。因此，将任何 Parcel 数据放入持久存储是不合适的：Parcel 中任何数据的底层实现的更改可能会使旧数据无法读取。
回答by Cristan
Since parcelable doesn't help to place your data in persistent storage (see StenSoft's answer), you can use gson to persist your Location instead:
由于 Parcelable 无助于将您的数据放置在持久存储中（请参阅 StenSoft 的回答），您可以使用 gson 来保存您的位置：
Saving a Location:
保存位置：
val json = Gson().toJson(location)
sharedPreferences.edit().putString("location", json).apply()
Retrieving a Location:
检索位置：
val json = sharedPreferences.getString("location", null)
return Gson().fromJson(json, Location::class.java)
In case you're still using Java, replace valwith String, Gson()with new Gson(), ::class.javawith .classand end each line with a semicolumn.
如果你还在使用Java，更换val用String，Gson()用new Gson()，::class.java用.class而结束与semicolumn每一行。
回答by LowFieldTheory
The preferred way would be to implement an IntentServiceprobably
首选的办法是实施IntentService可能
