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
这是@d60402回答的修改版本:https://stackoverflow.com/a/15573121/4747587
按照上面提到的去做。但是,与其有一个Base Activity,并将其作为每个活动的父活动,并重写onResume()和onPause,不如执行以下操作:
在你的应用程序类中,添加这样一行:
registerActivityLifecycleCallbacks(应用程序。ActivityLifecycleCallbacks回调);
这个回调有所有的活动生命周期方法,你现在可以覆盖onactivityresume()和onActivityPaused()。
看看这个Gist: https://gist.github.com/thsaravana/1fa576b6af9fc8fff20acfb2ac79fa1b
其他回答
onPause()和onResume()方法在应用程序被带到后台并再次进入前台时被调用。但是,在应用程序第一次启动时和关闭之前也会调用它们。你可以在活动中阅读更多。
没有任何直接的方法来获得应用程序的状态,而在后台或前台,但即使我已经面临这个问题,并找到解决方案与onWindowFocusChanged和onStop。
更多细节请查看这里Android:解决方案检测当一个Android应用程序去后台,回到前台没有getRunningTasks或getRunningAppProcesses。
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)
{
}
}
LifecycleObserver已弃用。使用DefaultLifecycleObserver代替:
public class YourApplication extends Application implements DefaultLifecycleObserver {
@Override
public void onCreate() {
super.onCreate();
ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
}
@Override
public void onStart(@NonNull LifecycleOwner owner) {
DefaultLifecycleObserver.super.onStart(owner);
}
@Override
public void onResume(@NonNull LifecycleOwner owner) {
DefaultLifecycleObserver.super.onResume(owner);
}
@Override
public void onPause(@NonNull LifecycleOwner owner) {
DefaultLifecycleObserver.super.onPause(owner);
}
@Override
public void onStop(@NonNull LifecycleOwner owner) {
DefaultLifecycleObserver.super.onStop(owner);
}
@Override
public void onDestroy(@NonNull LifecycleOwner owner) {
DefaultLifecycleObserver.super.onDestroy(owner);
}
}
依赖关系:
implementation 'androidx.lifecycle:lifecycle-common:2.5.1'
implementation 'androidx.lifecycle:lifecycle-process:2.5.1'
我的解决方案受到@d60402的答案的启发,也依赖于一个时间窗口,但不使用定时器:
public abstract class BaseActivity extends ActionBarActivity {
protected boolean wasInBackground = false;
@Override
protected void onStart() {
super.onStart();
wasInBackground = getApp().isInBackground;
getApp().isInBackground = false;
getApp().lastForegroundTransition = System.currentTimeMillis();
}
@Override
protected void onStop() {
super.onStop();
if( 1500 < System.currentTimeMillis() - getApp().lastForegroundTransition )
getApp().isInBackground = true;
}
protected SingletonApplication getApp(){
return (SingletonApplication)getApplication();
}
}
其中SingletonApplication是Application类的扩展:
public class SingletonApplication extends Application {
public boolean isInBackground = false;
public long lastForegroundTransition = 0;
}
2021年11月更新
实际设置如下
class App : Application() {
override fun onCreate() {
super.onCreate()
ProcessLifecycleOwner.get().lifecycle.addObserver(AppLifecycleListener())
}
}
class AppLifecycleListener : DefaultLifecycleObserver {
override fun onStart(owner: LifecycleOwner) { // app moved to foreground
}
override fun onStop(owner: LifecycleOwner) { // app moved to background
}
}
依赖关系
implementation "androidx.lifecycle:lifecycle-process:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-common:$lifecycle_version"
原来的答案
ProcessLifecycleOwner似乎也是一个很有前途的解决方案。
ProcessLifecycleOwner将分派ON_START, ON_RESUME事件,当第一个活动通过这些事件时。ON_PAUSE, ON_STOP,事件将在最后一个活动通过它们后延迟分派。这个延迟足够长,可以保证ProcessLifecycleOwner在由于配置更改而销毁和重新创建活动时不会发送任何事件。
实现可以简单到
class AppLifecycleListener : LifecycleObserver {
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun onMoveToForeground() { // app moved to foreground
}
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
fun onMoveToBackground() { // app moved to background
}
}
// register observer
ProcessLifecycleOwner.get().lifecycle.addObserver(AppLifecycleListener())
根据源代码,当前延迟值为700ms。
使用此特性还需要依赖项:
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycleVersion"
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