如何在Kotlin中使用Single Live Event展示烤面包 [英] How to use Single Live Event to show toast in Kotlin
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问题描述
我想使用单个直播事件类来显示吐司(例如标志) 这是我尝试的代码. 我不想使用像标志这样的peding.我该如何解决?
I want to use single live event class to show toast (like flag) Here is my code what I tried. I want to not use peding like flag. how do I fix it?
MainViewModel
class MainViewModel(private val movieRepository: MovieRepository) : ViewModel() {
val keyword = MutableLiveData<String>()
val movieList = MutableLiveData<List<Movie>>()
val msg = MutableLiveData<String>()
val pending: AtomicBoolean = AtomicBoolean(false)
fun findMovie() {
val keywordValue = keyword.value ?: return
pending.set(true)
if (keywordValue.isNullOrBlank()) {
msg.value = "emptyKeyword"
return
}
movieRepository.getMovieData(keyword = keywordValue, 30,
onSuccess = {
if (it.items!!.isEmpty()) {
msg.value = "emptyResult"
} else {
msg.value = "success"
movieList.value = it.items
}
},
onFailure = {
msg.value = "fail"
}
)
}
}
MainActivity
private fun viewModelCallback() {
mainViewModel.msg.observe(this, {
if (mainViewModel.pending.compareAndSet(true, false)) {
when (it) {
"success" -> toast(R.string.network_success)
"emptyKeyword" -> toast(R.string.keyword_empty)
"fail" -> toast(R.string.network_error)
"emptyResult" -> toast(R.string.keyword_result_empty)
}
}
})
}
推荐答案
解决方案
第1步.将SingleLiveEvent.kt
复制到您的应用中
/*
* Copyright 2017 Google Inc.
*
* 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
*
* http://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.
*/
package com.example.myapp;
import android.util.Log;
import androidx.annotation.MainThread;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.Observer;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A lifecycle-aware observable that sends only new updates after subscription, used for events like
* navigation and Snackbar messages.
* <p>
* This avoids a common problem with events: on configuration change (like rotation) an update
* can be emitted if the observer is active. This LiveData only calls the observable if there's an
* explicit call to setValue() or call().
* <p>
* Note that only one observer is going to be notified of changes.
*/
public class SingleLiveEvent<T> extends MutableLiveData<T> {
private static final String TAG = "SingleLiveEvent";
private final AtomicBoolean mPending = new AtomicBoolean(false);
@MainThread
public void observe(@NonNull LifecycleOwner owner, @NonNull Observer<? super T> observer) {
if (hasActiveObservers()) {
Log.w(TAG, "Multiple observers registered but only one will be notified of changes.");
}
// Observe the internal MutableLiveData
super.observe(owner, t -> {
if (mPending.compareAndSet(true, false)) {
observer.onChanged(t);
}
});
}
@MainThread
public void setValue(@Nullable T t) {
mPending.set(true);
super.setValue(t);
}
/**
* Used for cases where T is Void, to make calls cleaner.
*/
@MainThread
public void call() {
setValue(null);
}
}
第2步.从代码中使用.
MainViewModel
class MainViewModel(private val movieRepository: MovieRepository) : ViewModel() {
val keyword = MutableLiveData<String>()
val movieList = MutableLiveData<List<Movie>>()
val msg = SingleLiveEvent<String>()
fun findMovie() {
val keywordValue = keyword.value ?: return
if (keywordValue.isNullOrBlank()) {
msg.value = "emptyKeyword"
return
}
movieRepository.getMovieData(keyword = keywordValue, 30,
onSuccess = {
if (it.items!!.isEmpty()) {
msg.value = "emptyResult"
} else {
msg.value = "success"
movieList.value = it.items
}
},
onFailure = {
msg.value = "fail"
}
)
}
}
MainActivity
private fun viewModelCallback() {
mainViewModel.msg.observe(this, {
when (it) {
"success" -> toast(R.string.network_success)
"emptyKeyword" -> toast(R.string.keyword_empty)
"fail" -> toast(R.string.network_error)
"emptyResult" -> toast(R.string.keyword_result_empty)
}
})
}
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