我试图通过一个意图传递一个自定义对象的Hashmap。
我试图使用parcelable,因为我读到的是android中正确的方法(即parcelable高于serializable)。
然而,当我尝试使用getParcelable获取hashmap时,它无法在意图中找到我的hashmap,但getSerializable可以。
使用serializable来做hashmaps可以吗?这是我唯一的选择吗?
你当然可以序列化你的地图,只要你的Objects是可序列化的。你也可以创建一个单独的单人类(DataStore之类的)来保存你的数据。这样你就不需要将数据从Activity传递到Activity。或者,更简单的,把数据保存在一个公共静态变量中。
java.util.HashMap 不是 包裹式,所以你的选择是
你必须添加一个 "包装"。它很丑陋,但工作...
/**
* Provides a way to wrap a serializable {@link Map} in order to preserve its class
* during serialization inside an {@link Intent}, otherwise it would be "flattened"
* in a {@link android.os.Parcel} and unparceled as a {@link java.util.HashMap}.
*/
public class MapWrapper<T extends Map & Serializable> implements Serializable {
private final T map;
public MapWrapper(@NonNull T map) {
this.map = map;
}
public T getMap() {
return map;
}
/**
* Add extra map data to the intent. The name must include a package prefix, for example
* the app com.android.contacts would use names like "com.android.contacts.ShowAll".
* <p>
* The provided map will be wrapped to preserve its class during serialization.
* Use {@link #getMapExtra(Intent, String)} to deserialize it.
*
* @param intent The intent to add data to.
* @param name The name of the extra data, with package prefix.
* @param map The map data value.
*
* @return The same {@link Intent} object, for chaining multiple calls into a single statement.
*
* @see Intent#putExtra(String, Serializable)
*/
@NonNull
public static <T extends Map & Serializable> Intent putMapExtra(
@NonNull Intent intent, @NonNull String name, @NonNull T map) {
return intent.putExtra(name, new MapWrapper<>(map));
}
/**
* Retrieve extra map data from the intent.
*
* @param intent The intent to retrieve data from.
* @param name The name of the desired extra item.
*
* @return The value of an extra map item that was previously added with
* {@link #putMapExtra(Intent, String, Map)} or {@code null} if no data was found.
*
* @throws ClassCastException
* If the {@link Serializable} object with the specified name is not of type
* {@link MapWrapper} or if the wrapped {@code Map} is not of type {@link T}.
*
* @see Intent#getSerializableExtra(String)
*/
@Nullable
public static <T extends Map & Serializable> T getMapExtra(
@NonNull Intent intent, @NonNull String name)
throws ClassCastException {
final Serializable s = intent.getSerializableExtra(name);
//noinspection unchecked
return s == null ? null : ((MapWrapper<T>)s).getMap();
}
}
更多信息 https:/medium.comthe-wtfilesthe-mysterious-case-the-bundle-and-the-map-7b15279a794e