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Multiple observe single LiveData.
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package [YOUR PACKAGE] | |
/* | |
* Copyright 2018 Google LLC | |
* | |
* Licensed under the Apache License, Version 2.0 (the "License"); | |
* you may not use this file except in compliance with the License. | |
* You may obtain a copy of the License at | |
* | |
* https://www.apache.org/licenses/LICENSE-2.0 | |
* | |
* Unless required by applicable law or agreed to in writing, software | |
* distributed under the License is distributed on an "AS IS" BASIS, | |
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
* See the License for the specific language governing permissions and | |
* limitations under the License. | |
*/ | |
/* | |
* Copyright 2020 yasukotelin | |
* | |
* Licensed under the Apache License, Version 2.0 (the "License"); | |
* you may not use this file except in compliance with the License. | |
* You may obtain a copy of the License at | |
* | |
* https://www.apache.org/licenses/LICENSE-2.0 | |
* | |
* Unless required by applicable law or agreed to in writing, software | |
* distributed under the License is distributed on an "AS IS" BASIS, | |
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
* See the License for the specific language governing permissions and | |
* limitations under the License. | |
*/ | |
import androidx.lifecycle.Observer | |
/** | |
* Used as a wrapper for data that is exposed via a LiveData that represents an event. | |
*/ | |
open class Event<out T>(private val content: T) { | |
// for multiple observe. | |
private val tagMap: MutableMap<String, Boolean> = mutableMapOf() | |
// for single observe. | |
private var hasBeenHandled = false | |
/** | |
* Returns the content if don't call this yet. | |
* @param tag if you want to observe multiple, should specify tag. | |
*/ | |
fun getContentIfNotHandled(tag: String? = null): T? { | |
return if (tag == null) { | |
if (hasBeenHandled) { | |
null | |
} else { | |
hasBeenHandled = true | |
content | |
} | |
} else { | |
if (tagMap[tag] == null) { | |
tagMap.put(tag, true) | |
content | |
} else { | |
null | |
} | |
} | |
} | |
/** | |
* Returns the content, even if it's already been handled. | |
*/ | |
fun peekContent(): T = content | |
} | |
/** | |
* An [Observer] for [Event]s, simplifying the pattern of checking if the [Event]'s content has | |
* already been handled. | |
* | |
* @param tag if you want to observe multiple, should specify tag. | |
* @param onEventUnhandledContent is *only* called if the [Event]'s contents has not been handled. | |
*/ | |
class EventObserver<T>( | |
private val tag: String? = null, | |
private val onEventUnhandledContent: (T) -> Unit | |
) : Observer<Event<T>> { | |
override fun onChanged(event: Event<T>?) { | |
event?.getContentIfNotHandled(tag)?.let { value -> | |
onEventUnhandledContent(value) | |
} | |
} | |
} |
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