问Android:检测应用程序是否进入后台
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Stack Overflow用户

提问于 2019-11-11 13:28:41

回答 4查看 6K关注 0票数 4

这似乎是关于这个问题的答案的音调，但都不完整。A有一个具有多种活动的应用程序。我所需要的只是一个IF语句，这意味着如果我的应用程序进入一个背景，我会这样做.如果它进入前台我就这么做..。

!!！请记住，如果我从一个活动切换到另一个活动--这意味着我的第一个活动停止了，这并不意味着我的应用程序进入了后台--只是一个活动被另一个活动所取代。

android

回答 4

Stack Overflow用户

发布于 2019-11-11 14:01:57

首先，在应用程序级梯度中添加一些必要的依赖项

dependencies {
def lifecycle_version = "2.1.0"

// ViewModel and LiveData
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
// alternatively - just ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version" // For Kotlin use lifecycle-viewmodel-ktx
// alternatively - just LiveData
implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version"
// alternatively - Lifecycles only (no ViewModel or LiveData). Some UI
//     AndroidX libraries use this lightweight import for Lifecycle
implementation "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"

annotationProcessor "androidx.lifecycle:lifecycle-compiler:$lifecycle_version" // For Kotlin use kapt instead of annotationProcessor
// alternately - if using Java8, use the following instead of lifecycle-compiler
implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"

// optional - ReactiveStreams support for LiveData
implementation "androidx.lifecycle:lifecycle-reactivestreams:$lifecycle_version" // For Kotlin use lifecycle-reactivestreams-ktx

// optional - Test helpers for LiveData
testImplementation "androidx.arch.core:core-testing:$lifecycle_version"

}

您可以在这里引用最新版本的依赖项。

https://developer.android.com/jetpack/androidx/releases/lifecycle?authuser=1

您的应用程序必须扩展Application类，并覆盖下面示例中给出的以下方法。

您可以简单地使用arch库的生命周期感知组件实现相同的功能。我刚刚为您的用例发布了一个用于Kotlin和Java的示例代码。

Java版本。

public class YourApp extends Application implements LifecycleObserver {

@Override
public void onCreate() {
    super.onCreate();

    ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
}

// Application level lifecycle events
@OnLifecycleEvent(Lifecycle.Event.ON_START)
public void onEnteredForeground() {
    //Timber.d("Application did enter foreground");

}

@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
public void onEnteredBackground() {
   // Timber.d("Application did enter background");
}

}

Kotlin版本：

class ZumeApp : Application(), LifecycleObserver {

override fun onCreate() {
    super.onCreate()
    ProcessLifecycleOwner.get().lifecycle.addObserver(this)
}

// Application level lifecycle events
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun onEnteredForeground() {
    Timber.d("Application did enter foreground")

}

@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
fun onEnteredBackground() {
    Timber.d("Application did enter background")
}
}

我希望它能帮到你。如果它不起作用，或者在android文档中引用下面的文章，请留下评论。

https://developer.android.com/topic/libraries/architecture/lifecycle?authuser=1

票数 3

Stack Overflow用户

发布于 2019-11-11 13:50:31

ProcessLifecycleOwner是有帮助的东西。它提到了It is useful for use cases where you would like to react on your app coming to the foreground or going to the background and you don't need a milliseconds accuracy in receiving lifecycle events.

https://developer.android.com/reference/androidx/lifecycle/ProcessLifecycleOwner.html

看看事件Lifecycle.Event.ON_PAUSE和Lifecycle.Event.ON_RESUME

票数 1

Stack Overflow用户

发布于 2019-11-11 15:58:01

好的，它是通过在观察者中使用ProcessLifecycleOwner来完成的。我的碎片上有这个。状态从ON_PAUSE变为ON_RESUME和back的唯一时间是整个应用程序进入后台并返回的时候。然后，取决于状态(在我的示例中)，我要么使用背景方法获得我的位置，要么使用前台回调。

@Override
public View onCreateView(@NonNull LayoutInflater inflater, final ViewGroup container, Bundle savedInstanceState) {

    setRetainInstance(true);
    //...
    // some other stuff
    //...

    ProcessLifecycleOwner.get().getLifecycle().addObserver(new LifecycleEventObserver() {
        @Override
        public void onStateChanged(@NonNull LifecycleOwner source, @NonNull Lifecycle.Event event) {

            if (event == Lifecycle.Event.ON_PAUSE) {
                Log.e("Lifecycle", "Background");


                getLocationFromBackground();


            } else if (event == Lifecycle.Event.ON_RESUME) {
                Log.e("Lifecycle", "Foreground");

                getLocationFromForeground();
            }
        }
    });

return view;
}

private void getLocationFromBackground() {
    // some code
}


private void getLocationFromForeground() {
    // some code
}