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
我发现了一个很好的方法来检测应用程序是否进入前台或后台。 这是我的代码。 希望这对你有帮助。
/**
* Custom Application which can detect application state of whether it enter
* background or enter foreground.
*
* @reference http://www.vardhan-justlikethat.blogspot.sg/2014/02/android-solution-to-detect-when-android.html
*/
public abstract class StatusApplication extends Application implements ActivityLifecycleCallbacks {
public static final int STATE_UNKNOWN = 0x00;
public static final int STATE_CREATED = 0x01;
public static final int STATE_STARTED = 0x02;
public static final int STATE_RESUMED = 0x03;
public static final int STATE_PAUSED = 0x04;
public static final int STATE_STOPPED = 0x05;
public static final int STATE_DESTROYED = 0x06;
private static final int FLAG_STATE_FOREGROUND = -1;
private static final int FLAG_STATE_BACKGROUND = -2;
private int mCurrentState = STATE_UNKNOWN;
private int mStateFlag = FLAG_STATE_BACKGROUND;
@Override
public void onCreate() {
super.onCreate();
mCurrentState = STATE_UNKNOWN;
registerActivityLifecycleCallbacks(this);
}
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
// mCurrentState = STATE_CREATED;
}
@Override
public void onActivityStarted(Activity activity) {
if (mCurrentState == STATE_UNKNOWN || mCurrentState == STATE_STOPPED) {
if (mStateFlag == FLAG_STATE_BACKGROUND) {
applicationWillEnterForeground();
mStateFlag = FLAG_STATE_FOREGROUND;
}
}
mCurrentState = STATE_STARTED;
}
@Override
public void onActivityResumed(Activity activity) {
mCurrentState = STATE_RESUMED;
}
@Override
public void onActivityPaused(Activity activity) {
mCurrentState = STATE_PAUSED;
}
@Override
public void onActivityStopped(Activity activity) {
mCurrentState = STATE_STOPPED;
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
@Override
public void onActivityDestroyed(Activity activity) {
mCurrentState = STATE_DESTROYED;
}
@Override
public void onTrimMemory(int level) {
super.onTrimMemory(level);
if (mCurrentState == STATE_STOPPED && level >= TRIM_MEMORY_UI_HIDDEN) {
if (mStateFlag == FLAG_STATE_FOREGROUND) {
applicationDidEnterBackground();
mStateFlag = FLAG_STATE_BACKGROUND;
}
}else if (mCurrentState == STATE_DESTROYED && level >= TRIM_MEMORY_UI_HIDDEN) {
if (mStateFlag == FLAG_STATE_FOREGROUND) {
applicationDidDestroyed();
mStateFlag = FLAG_STATE_BACKGROUND;
}
}
}
/**
* The method be called when the application been destroyed. But when the
* device screen off,this method will not invoked.
*/
protected abstract void applicationDidDestroyed();
/**
* The method be called when the application enter background. But when the
* device screen off,this method will not invoked.
*/
protected abstract void applicationDidEnterBackground();
/**
* The method be called when the application enter foreground.
*/
protected abstract void applicationWillEnterForeground();
}
其他回答
这是我的解决方案https://github.com/doridori/AndroidUtils/blob/master/App/src/main/java/com/doridori/lib/app/ActivityCounter.java
基本上涉及到用计时器计算所有Activity的生命周期方法,以捕捉当前前台没有活动但应用程序(即在旋转)的情况
使用ProcessLifecycleOwner,这非常简单
添加这些依赖项
implementation "android.arch.lifecycle:extensions:$project.archLifecycleVersion"
kapt "android.arch.lifecycle:compiler:$project.archLifecycleVersion"
在芬兰湾的科特林:
class ForegroundBackgroundListener : LifecycleObserver {
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun startSomething() {
Log.v("ProcessLog", "APP IS ON FOREGROUND")
}
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
fun stopSomething() {
Log.v("ProcessLog", "APP IS IN BACKGROUND")
}
}
然后在你的基本活动中:
override fun onCreate() {
super.onCreate()
ProcessLifecycleOwner.get()
.lifecycle
.addObserver(
ForegroundBackgroundListener()
.also { appObserver = it })
}
请看我关于这个主题的文章: https://medium.com/@egek92/how-to-actually-detect-foreground-background-changes-in-your-android-application-without-wanting-9719cc822c48
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
这里有一个解决方案,通过使用deboning逻辑,确保我们不会得到连续的背景/前景事件。所以,它总是反映一种稳定的背景/前景状态。
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import androidx.lifecycle.LifecycleOwner
import java.util.Timer
import java.util.TimerTask
/**
* An observer class to listen on the app's lifecycle.
*/
class AppLifecycleObserver(
private val onAppGoesToBackground: () -> Unit = {},
private val onAppEntersForeground: () -> Unit = {}
) : LifecycleEventObserver {
private val debounce = DebouncingTimer(timeout = 10)
override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
debounce.refresh {
when (event.targetState) {
Lifecycle.State.CREATED -> onAppGoesToBackground()
Lifecycle.State.RESUMED -> onAppEntersForeground()
else -> Unit
}
}
}
fun attach() {
ProcessLifecycleOwner.get().lifecycle.addObserver(this)
}
fun detach() {
ProcessLifecycleOwner.get().lifecycle.removeObserver(this)
}
private class DebouncingTimer(private val timeout: Long) {
private var timer: Timer? = null
fun refresh(job: () -> Unit) {
timer?.cancel()
timer = Timer()
timer?.schedule(object : TimerTask() {
override fun run() = job.invoke()
}, timeout)
}
}
}
只需要创建一个AppLifecycleObserver实例:
private val appLifecycleObserver = AppLifecycleObserver(
onAppGoesToBackground = { // do whatever... },
onAppEntersForeground = { // do whatever... }
)
// Attach the observer when it is needed:
appLifecycleObserver.attach()
// Remove when there is no need to it:
appLifecycleObserver.detach()
不要忘记添加一个合适的依赖版本:
implementation("androidx.lifecycle:lifecycle-process:$lifecycle_version")
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
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