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
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
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
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
我知道有点晚了,但我认为所有这些答案都有一些问题,而我这样做了,这是完美的。
创建一个活动生命周期回调,如下所示:
class ActivityLifeCycle implements ActivityLifecycleCallbacks{
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
@Override
public void onActivityStarted(Activity activity) {
}
Activity lastActivity;
@Override
public void onActivityResumed(Activity activity) {
//if (null == lastActivity || (activity != null && activity == lastActivity)) //use this condition instead if you want to be informed also when app has been killed or started for the first time
if (activity != null && activity == lastActivity)
{
Toast.makeText(MyApp.this, "NOW!", Toast.LENGTH_LONG).show();
}
lastActivity = activity;
}
@Override
public void onActivityPaused(Activity activity) {
}
@Override
public void onActivityStopped(Activity activity) {
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
@Override
public void onActivityDestroyed(Activity activity) {
}
}
然后像下面这样在你的应用类上注册它:
public class MyApp extends Application {
@Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(new ActivityLifeCycle());
}
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。
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