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
我设法监控应用导航到后台和回前台通过实现一个BaseActivity,利用onResume, onPause和onStop活动回调的使用。这是我的实现。
override fun onResume() {
super.onResume()
if (AppActivityState.state == AppState.ON_LAUNCHED) {
// We are in the first launch.
onLaunched()
} else {
if (AppActivityState.state == AppState.ON_BACKGROUND) {
// We came from background to foreground.
AppActivityState.state = AppState.ON_FOREGROUND
onForeground()
} else {
// We are just navigating through pages.
AppActivityState.state = AppState.RESUMED
}
}
}
override fun onPause() {
super.onPause()
// If state is followed by onStop then it means we will going to background.
AppActivityState.state = AppState.PAUSED
}
override fun onStop() {
super.onStop()
// App will go to background base on the 'pause' cue.
if (AppActivityState.state == AppState.PAUSED) {
AppActivityState.state = AppState.ON_BACKGROUND
onBackground()
}
}
在创建BaseActivity之后,你只需要将这个activity扩展到应用程序中的任何activity。
在这些类型的实现中,您可以准确地检测到以下内容: onBackground >应用程序将进入后台 onForeground >应用将返回前台 onLaunch >应用程序刚刚打开
我希望这对你有帮助:)
其他回答
这个解决方案呢
public class BaseActivity extends Activity
{
static String currentAct = "";
@Override
protected void onStart()
{
super.onStart();
if (currentAct.equals(""))
Toast.makeText(this, "Start", Toast.LENGTH_LONG).show();
currentAct = getLocalClassName();
}
@Override
protected void onStop()
{
super.onStop();
if (currentAct.equals(getLocalClassName()))
{
currentAct = "";
Toast.makeText(this, "Stop", Toast.LENGTH_LONG).show();
}
}
}
所有的Activity都需要扩展BaseActivity。
当一个活动调用另一个(A->B)时,currentAct不等于getLocalClassName(),因为第二个活动(B)的onStart()在第一个(A) (https://developer.android.com/guide/components/activities.html#CoordinatingActivities)的onStop()之前被调用。
当用户按下home键或应用程序之间的变化将只调用onStop(),然后currentAct等于getLocalClassName()。
您可以在ActivityLifecycleCallbacks和ComponentCallbacks2的帮助下轻松实现这一点。
创建一个实现上述接口的类AppLifeCycleHandler。
package com.sample.app;
import android.app.Activity;
import android.app.Application;
import android.content.ComponentCallbacks2;
import android.content.res.Configuration;
import android.os.Bundle;
/**
* Created by Naveen on 17/04/18
*/
public class AppLifeCycleHandler
implements Application.ActivityLifecycleCallbacks, ComponentCallbacks2 {
AppLifeCycleCallback appLifeCycleCallback;
boolean appInForeground;
public AppLifeCycleHandler(AppLifeCycleCallback appLifeCycleCallback) {
this.appLifeCycleCallback = appLifeCycleCallback;
}
@Override
public void onActivityResumed(Activity activity) {
if (!appInForeground) {
appInForeground = true;
appLifeCycleCallback.onAppForeground();
}
}
@Override
public void onTrimMemory(int i) {
if (i == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
appInForeground = false;
appLifeCycleCallback.onAppBackground();
}
}
@Override
public void onActivityCreated(Activity activity, Bundle bundle) {
}
@Override
public void onActivityStarted(Activity activity) {
}
@Override
public void onActivityPaused(Activity activity) {
}
@Override
public void onActivityStopped(Activity activity) {
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {
}
@Override
public void onActivityDestroyed(Activity activity) {
}
@Override
public void onConfigurationChanged(Configuration configuration) {
}
@Override
public void onLowMemory() {
}
interface AppLifeCycleCallback {
void onAppBackground();
void onAppForeground();
}
}
在你的类中,当应用程序在前台和后台之间切换时,应用程序实现AppLifeCycleCallback来获得回调。如下图所示。
public class BaseApplication extends Application implements AppLifeCycleHandler.AppLifeCycleCallback{
@Override
public void onCreate() {
super.onCreate();
AppLifeCycleHandler appLifeCycleHandler = new AppLifeCycleHandler(this);
registerActivityLifecycleCallbacks(appLifeCycleHandler);
registerComponentCallbacks(appLifeCycleHandler);
}
@Override
public void onAppBackground() {
Log.d("LifecycleEvent", "onAppBackground");
}
@Override
public void onAppForeground() {
Log.d("LifecycleEvent", "onAppForeground");
}
}
希望这能有所帮助。
编辑 作为替代方案,您现在可以使用生命周期感知的体系结构组件。
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
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:$lifecycleVersion"
这里有一个解决方案,通过使用deboning逻辑,确保我们不会得到连续的背景/前景事件。所以,它总是反映一种稳定的背景/前景状态。
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import androidx.lifecycle.LifecycleOwner
import java.util.Timer
import java.util.TimerTask
/**
* An observer class to listen on the app's lifecycle.
*/
class AppLifecycleObserver(
private val onAppGoesToBackground: () -> Unit = {},
private val onAppEntersForeground: () -> Unit = {}
) : LifecycleEventObserver {
private val debounce = DebouncingTimer(timeout = 10)
override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
debounce.refresh {
when (event.targetState) {
Lifecycle.State.CREATED -> onAppGoesToBackground()
Lifecycle.State.RESUMED -> onAppEntersForeground()
else -> Unit
}
}
}
fun attach() {
ProcessLifecycleOwner.get().lifecycle.addObserver(this)
}
fun detach() {
ProcessLifecycleOwner.get().lifecycle.removeObserver(this)
}
private class DebouncingTimer(private val timeout: Long) {
private var timer: Timer? = null
fun refresh(job: () -> Unit) {
timer?.cancel()
timer = Timer()
timer?.schedule(object : TimerTask() {
override fun run() = job.invoke()
}, timeout)
}
}
}
只需要创建一个AppLifecycleObserver实例:
private val appLifecycleObserver = AppLifecycleObserver(
onAppGoesToBackground = { // do whatever... },
onAppEntersForeground = { // do whatever... }
)
// Attach the observer when it is needed:
appLifecycleObserver.attach()
// Remove when there is no need to it:
appLifecycleObserver.detach()
不要忘记添加一个合适的依赖版本:
implementation("androidx.lifecycle:lifecycle-process:$lifecycle_version")
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