结合AtomicInteger判断应用是否在后台显示

 private AtomicInteger mFinalCount = new AtomicInteger(0);

        application.registerActivityLifecycleCallbacks(new Application
                .ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

            }

            @Override
            public void onActivityStarted(Activity activity) {
                int count = mFinalCount.incrementAndGet();
                if (count == 1) {
                    // 从后台转到了前台
          
                }
            }

            @Override
            public void onActivityResumed(Activity activity) {

            }

            @Override
            public void onActivityPaused(Activity activity) {

            }

            @Override
            public void onActivityStopped(Activity activity) {
                int count = mFinalCount.decrementAndGet();
                if (count == 0) {
                    // 从前台转到了后台
                  
                }
            }

            @Override
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

            }

            @Override
            public void onActivityDestroyed(Activity activity) {

            }
        });