Android 应用监听后台切换前台的方法

Android在SDK14的时候提供了一个Callback。ActivityLifecycleCallbacks，你可以通过这个Callback拿到App所有Activity的生命周期回调。通过对比ActivityLifecycleCallbacks中onActivityStarted返回的activity实例与上一个返回的实例进行对比，如果不相同，说明应用一直在前台activity之间进行切换，如果相同，则说明应用从后台切换到前台。通过回调触发事件。代码如下：

private void LifeCallBack(){
registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {

@Override
public void onActivityStopped(Activity activity) {
}

@Override
public void onActivityStarted(Activity activity) {
if (activity_old==null){
activity_old=activity;
}else {
if (activity_old!=activity){
activity_old=activity;
}else {
checkLifeback.appStatus();
}
}
}

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

@Override
public void onActivityResumed(Activity activity) {
}

@Override
public void onActivityPaused(Activity activity) {
}

@Override
public void onActivityDestroyed(Activity activity) {
}

@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
});

}
public interface CheckLifeBack{
void appStatus();
}
public static CheckLifeBack checkLifeback;
public  static void setOnCheckLifeBack(CheckLifeBack checkLifeBack){
checkLifeback=checkLifeBack;
}