我试图写一个应用程序,做一些具体的时候,它被带回前台后一段时间。是否有一种方法可以检测应用程序是被发送到后台还是被带到前台?
当前回答
我喜欢ProcessLifecycleOwner方法,但实际上可以跳过所有这些,因为在Activity的onCreate()方法中,可以很容易地确定它是第一次运行还是后续运行:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
/* savedInstanceState is always null on first run */
} else {
/* it's a subsequent run */
}
}
其他回答
lifecycle包提供了类和接口,让您可以构建生命周期感知的组件
您的应用程序应该实现LifecycleObserver接口:
public class MyApplication extends Application implements LifecycleObserver {
@Override
public void onCreate() {
super.onCreate();
ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
}
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
private void onAppBackgrounded() {
Log.d("MyApp", "App in background");
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
private void onAppForegrounded() {
Log.d("MyApp", "App in foreground");
}
}
为此,您需要将此依赖项添加到构建中。gradle文件:
dependencies {
implementation "android.arch.lifecycle:extensions:1.1.1"
}
正如谷歌所建议的,你应该最小化在activity的生命周期方法中执行的代码:
一种常见的模式是实现依赖的操作 活动和片段的生命周期方法中的组件。 然而,这种模式会导致代码组织不佳,并且导致 错误的扩散。通过使用生命周期感知组件,您 是否可以将依赖组件的代码移出生命周期方法 以及组件本身。
你可以在这里阅读更多: https://developer.android.com/topic/libraries/architecture/lifecycle
这些答案似乎不正确。当另一个活动开始和结束时,也会调用这些方法。你能做的是保留一个全局标志(是的,全局不好:),并在每次启动一个新活动时将其设置为true。在每个活动的onCreate中将其设置为false。然后,在onPause中检查这个标志。如果为假,你的应用就会进入后台,或者被杀死。
我使用这个解决方案: http://nathanael.hevenet.com/android-dev-detecting-when-your-app-is-in-the-background-across-activities/
简而言之——构建一个专门的服务,让每个活动向他报告每个生命周期事件,这个服务获得关于应用程序状态的信息。
很像@oldschool4664的解决方案,但在我看来更干净
由于我没有找到任何方法,它也处理旋转而不检查时间戳,我想我也分享我们现在如何在我们的应用程序中这样做。 对这个答案https://stackoverflow.com/a/42679191/5119746唯一的补充是,我们还考虑了方向。
class MyApplication : Application(), Application.ActivityLifecycleCallbacks {
// Members
private var mAppIsInBackground = false
private var mCurrentOrientation: Int? = null
private var mOrientationWasChanged = false
private var mResumed = 0
private var mPaused = 0
然后,对于回调,我们首先有简历:
// ActivityLifecycleCallbacks
override fun onActivityResumed(activity: Activity?) {
mResumed++
if (mAppIsInBackground) {
// !!! App came from background !!! Insert code
mAppIsInBackground = false
}
mOrientationWasChanged = false
}
和onActivityStopped:
override fun onActivityStopped(activity: Activity?) {
if (mResumed == mPaused && !mOrientationWasChanged) {
// !!! App moved to background !!! Insert code
mAppIsInBackground = true
}
然后,这里是附加的:检查方向变化:
override fun onConfigurationChanged(newConfig: Configuration) {
if (newConfig.orientation != mCurrentOrientation) {
mCurrentOrientation = newConfig.orientation
mOrientationWasChanged = true
}
super.onConfigurationChanged(newConfig)
}
就是这样。希望这能帮助到一些人:)
这是我的解决方案。只需在您的主Application类中注册这个ActivityLifecycleCallbacks。在评论中,我提到了一个用户配置文件活动边缘情况。该活动只是一个具有透明边缘的活动。
/**
* This class used Activity lifecycle callbacks to determine when the application goes to the
* background as well as when it is brought to the foreground.
*/
public class Foreground implements Application.ActivityLifecycleCallbacks
{
/**
* How long to wait before checking onStart()/onStop() count to determine if the app has been
* backgrounded.
*/
public static final long BACKGROUND_CHECK_DELAY_MS = 500;
private static Foreground sInstance;
private final Handler mMainThreadHandler = new Handler(Looper.getMainLooper());
private boolean mIsForeground = false;
private int mCount;
public static void init(final Application application)
{
if (sInstance == null)
{
sInstance = new Foreground();
application.registerActivityLifecycleCallbacks(sInstance);
}
}
public static Foreground getInstance()
{
return sInstance;
}
public boolean isForeground()
{
return mIsForeground;
}
public boolean isBackground()
{
return !mIsForeground;
}
@Override
public void onActivityStarted(final Activity activity)
{
mCount++;
// Remove posted Runnables so any Meteor disconnect is cancelled if the user comes back to
// the app before it runs.
mMainThreadHandler.removeCallbacksAndMessages(null);
if (!mIsForeground)
{
mIsForeground = true;
}
}
@Override
public void onActivityStopped(final Activity activity)
{
mCount--;
// A transparent Activity like community user profile won't stop the Activity that launched
// it. If you launch another Activity from the user profile or hit the Android home button,
// there are two onStops(). One for the user profile and one for its parent. Remove any
// posted Runnables so we don't get two session ended events.
mMainThreadHandler.removeCallbacksAndMessages(null);
mMainThreadHandler.postDelayed(new Runnable()
{
@Override
public void run()
{
if (mCount == 0)
{
mIsForeground = false;
}
}
}, BACKGROUND_CHECK_DELAY_MS);
}
@Override
public void onActivityCreated(final Activity activity, final Bundle savedInstanceState)
{
}
@Override
public void onActivityResumed(final Activity activity)
{
}
@Override
public void onActivityPaused(final Activity activity)
{
}
@Override
public void onActivitySaveInstanceState(final Activity activity, final Bundle outState)
{
}
@Override
public void onActivityDestroyed(final Activity activity)
{
}
}
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