所谓背景,指的是应用程序的所有活动当前对用户都不可见。
public class AppLifecycleService implements Application.ActivityLifecycleCallbacks {
private int created;
private boolean isSaveInstanceState;
private static AppLifecycleService instance;
private final static String TAG = AppLifecycleService.class.getName();
public static AppLifecycleService getInstance() {
if (instance == null) {
instance = new AppLifecycleService();
}
return instance;
}
public static boolean isApplicationRunning() {
boolean isApplicationRunning = true;
if (getCountCreatedActvities() == 0 && !isSaveInstanceState()) {
isApplicationRunning = false;
}
return isApplicationRunning;
}
public static boolean isSaveInstanceState() {
return AppLifecycleService.getInstance().isSaveInstanceState;
}
public static int getCountCreatedActvities() {
return AppLifecycleService.getInstance().created;
}
private AppLifecycleService() {
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
this.isSaveInstanceState = true;
}
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
++created;
}
@Override
public void onActivityDestroyed(Activity activity) {
--created;
}
@Override
public void onActivityResumed(Activity activity) { }
@Override
public void onActivityPaused(Activity activity) { }
@Override
public void onActivityStarted(Activity activity) { }
@Override
public void onActivityStopped(Activity activity) { }
}
唯一正确的解决方案:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
MyApp.mainActivity = this;
super.onCreate(savedInstanceState);
...
}
public class MyApp extends Application implements LifecycleObserver {
public static MainActivity mainActivity = null;
@Override
public void onCreate() {
super.onCreate();
ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
}
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
void onAppBackgrounded() {
// app in background
if (mainActivity != null) {
...
}
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
void onAppForegrounded() {
// app in foreground
if (mainActivity != null) {
...
}
}
}
没有任何解决方案适用于我,但是我提出了一个简单的解决方案。这应该可以解决问题。如果 isAppBackground 返回 false,那么应用程序必须在前台运行。
public static boolean isAppBackground(Context context){
boolean isBackground=true;
ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
if(Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT_WATCH){
List<ActivityManager.RunningAppProcessInfo> runningProcesses =activityManager.getRunningAppProcesses();
for(ActivityManager.RunningAppProcessInfo processInfo:runningProcesses){
if(processInfo.importance==ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND){
for(String activeProcess:processInfo.pkgList){
if(activeProcess.equals(context.getPackageName())){
isBackground = false;
}
}
}
}
}else{
List<ActivityManager.RunningTaskInfo> taskInfo = activityManager.getRunningTasks(1);
if(taskInfo.size()>0) {
ComponentName componentName = taskInfo.get(0).topActivity;
if(componentName.getPackageName().equals(context.getPackageName())){
isBackground = false;
}
}
}
return isBackground;
}
我自己实现了ActivityLifecycleCallbacks。我使用的是SherlockActivity,但对于普通的Activity类也可能适用。
首先,我创建了一个接口,包含了跟踪活动生命周期的所有方法:
public interface ActivityLifecycleCallbacks{
public void onActivityStopped(Activity activity);
public void onActivityStarted(Activity activity);
public void onActivitySaveInstanceState(Activity activity, Bundle outState);
public void onActivityResumed(Activity activity);
public void onActivityPaused(Activity activity);
public void onActivityDestroyed(Activity activity);
public void onActivityCreated(Activity activity, Bundle savedInstanceState);
}
其次,我在我的应用程序类中实现了这个接口:
public class MyApplication extends Application implements my.package.ActivityLifecycleCallbacks{
@Override
public void onCreate() {
super.onCreate();
}
@Override
public void onActivityStopped(Activity activity) {
Log.i("Tracking Activity Stopped", activity.getLocalClassName());
}
@Override
public void onActivityStarted(Activity activity) {
Log.i("Tracking Activity Started", activity.getLocalClassName());
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
Log.i("Tracking Activity SaveInstanceState", activity.getLocalClassName());
}
@Override
public void onActivityResumed(Activity activity) {
Log.i("Tracking Activity Resumed", activity.getLocalClassName());
}
@Override
public void onActivityPaused(Activity activity) {
Log.i("Tracking Activity Paused", activity.getLocalClassName());
}
@Override
public void onActivityDestroyed(Activity activity) {
Log.i("Tracking Activity Destroyed", activity.getLocalClassName());
}
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
Log.i("Tracking Activity Created", activity.getLocalClassName());
}
}
第三步,我正在创建一个继承自SherlockActivity的类:
public class MySherlockActivity extends SherlockActivity {
protected MyApplication nMyApplication;
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
nMyApplication = (MyApplication) getApplication();
nMyApplication.onActivityCreated(this, savedInstanceState);
}
protected void onResume() {
// TODO Auto-generated method stub
nMyApplication.onActivityResumed(this);
super.onResume();
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
nMyApplication.onActivityPaused(this);
super.onPause();
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
nMyApplication.onActivityDestroyed(this);
super.onDestroy();
}
@Override
protected void onStart() {
nMyApplication.onActivityStarted(this);
super.onStart();
}
@Override
protected void onStop() {
nMyApplication.onActivityStopped(this);
super.onStop();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
nMyApplication.onActivitySaveInstanceState(this, outState);
super.onSaveInstanceState(outState);
}
}
第四步,所有继承自SherlockActivity的类,我都替换成了MySherlockActivity:
public class MainActivity extends MySherlockActivity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
为了顺应CommonsWare和Key所说的,您可以扩展Application类,并让所有活动在其onPause/onResume方法中调用它。这将使您能够知道哪个Activity(ies)可见,但这可能可以更好地处理。
您能详细说明您的想法吗?当您说在后台运行时,您是否意味着即使当前不在屏幕上,您的应用程序仍然在内存中?您是否考虑过使用服务作为一种更持久的方式来管理您的应用程序,当它没有焦点时?
onPause()
或 onResume()
。 - CommonsWare系统区分前台应用和后台应用。 (与内存管理所使用的定义不同,服务限制中背景的定义是特指后台应用;一个应用可能对于内存管理来说处于后台状态,但对于其启动服务的能力来说却处于前台状态。) 如果以下任意一项为真,则视应用为在前台运行:
如果以上条件都不成立,则应用被视为在后台运行。
简单明了的回答:
override fun onPause() {
Log.i("APP LIFECYCLE", "App Enter BACKground")
isForeground = false
super.onPause()
}
override fun onResume() {
Log.i("APP LIFECYCLE", "App Enter FOREground")
isForeground = true
super.onResume()
}
isForeground
属性来检查状态即可。我建议您仔细阅读这个页面:http://developer.android.com/reference/android/app/Activity.html
简而言之,在调用onStop()
方法后,您的活动将不再可见。
onStop
之前是可见的;在 onPause
和 onStop
之间,它仍然是可见的,但不是在前台。 - nickgrimonStop()
后,活动将不再可见,这与您所写的相符。 - Key
@Override protected void onApplicationSentToBackground() { }
- Chuck D