[英]android indexoutofboundsexception passing bundle through intent
[英]Android - passing hashmap through intent
我正在嘗試通過意圖傳遞自定義對象的 Hashmap。
我正在嘗試使用parcelable,因為這就是我讀到的在android中做事的正確方法(即parcelable over serializable)。
但是,當我嘗試使用 getParcelable 獲取哈希圖時,它無法在意圖中找到我的哈希圖,但 getSerializable 可以。
可以對哈希圖使用可序列化嗎? 這是我唯一的選擇嗎?
您當然可以序列化您的地圖,只要您的對象是可序列化的。 您還可以做的是創建一個單獨的單例類(DataStore 左右?)來保存您的數據。 這樣您就不需要將數據從 Activity 傳遞到 Activity。 或者,更簡單的是,將數據保存在公共靜態變量中。
java.util.HashMap不是Parcelable ,所以你的選擇是:
您必須添加一個“包裝器”。 這是丑陋的,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();
}
}
有關https://medium.com/the-wtf-files/the-mysterious-case-of-the-bundle-and-the-map-7b15279a794e 的更多信息
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