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
您可以在应用程序类中简单地调用此方法
ProcessLifecycleOwner.get().getLifecycle().addObserver(new LifecycleEventObserver() {
@Override
public void onStateChanged(@NonNull LifecycleOwner source, @NonNull Lifecycle.Event event) {
Log.e(TAG, "onStateChanged: " + event.toString());
}
});
生命周期。事件将返回应用程序的状态
ON_CREATE
ON_START
ON_RESUME
ON_PAUSE
ON_STOP
ON_DESTROY
ON_ANY
当应用程序进入后台时,它将返回ON_PAUSE & ON_STOP 当应用程序进入前台时,将返回ON_START & ON_RESUME
其他回答
使用ProcessLifecycleOwner在Activity(或任何类)中从后台到前台检测app的示例。 当应用程序启动时,我缓存启动时间,然后在每个活动中,我将检查应用程序时间,以知道活动是否在第一时间启动或从后台启动
class MyApplication : Application(), LifecycleObserver {
var appStartBeginTime: Long? = null
override fun onCreate() {
super.onCreate()
ProcessLifecycleOwner.get().lifecycle.addObserver(this);
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun onMoveToForeground() {
Log.i("TAG", "onMoveToForeground")
appStartBeginTime = System.currentTimeMillis()
}
}
LoginActivity
class LoginActivity : AppCompatActivity() {
var localAppStartBeginTime: Long? = null
...
// Detect in onResume() instead of onStart because
// onMoveToForeground() in MyApplication will fired before onStart
override fun onResume() {
super.onResume()
if (isOpenedFirstTimeOrFromBackground()) {
Log.i("TAG", "open first time or from background")
// do something: eg, call API
} else {
Log.i("TAG", "on in another time")
}
}
private fun isOpenedFirstTimeOrFromBackground(): Boolean {
val globalStartBeginTime = (application as MyApplication).appStartBeginTime
if (localAppStartBeginTime != globalStartBeginTime) {
localAppStartBeginTime = globalStartBeginTime
return true
}
return false
}
}
安卓清单
<manifest ...>
<application
android:name=".MyApplication"
...>
</application>
</manifest>
演示 https://github.com/PhanVanLinh/AndroidDetectAppFromBackgroundToForeground
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
正确答案
创建名为MyApp的类,如下所示:
public class MyApp implements Application.ActivityLifecycleCallbacks, ComponentCallbacks2 {
private Context context;
public void setContext(Context context)
{
this.context = context;
}
private boolean isInBackground = false;
@Override
public void onTrimMemory(final int level) {
if (level == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
isInBackground = true;
Log.d("status = ","we are out");
}
}
@Override
public void onActivityCreated(Activity activity, Bundle bundle) {
}
@Override
public void onActivityStarted(Activity activity) {
}
@Override
public void onActivityResumed(Activity activity) {
if(isInBackground){
isInBackground = false;
Log.d("status = ","we are in");
}
}
@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() {
}
}
然后,在你想要的任何地方(最好是在应用程序中启动的第一个活动),添加下面的代码:
MyApp myApp = new MyApp();
registerComponentCallbacks(myApp);
getApplication().registerActivityLifecycleCallbacks(myApp);
完成了!现在当应用程序在后台时,我们得到日志状态:我们退出 当我们进入app,我们得到log status,我们是out
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。
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