使用Android导航组件获取Backstack状态 [英] Get Backstack status using android navigation component

问题描述

我想实现backpress行为，这样当您将backstack清空时按回车时会提示确认弹出窗口，否则它将弹出堆栈中的下一个片段.

我正在尝试获取后台堆栈数，但是我总是从两个片段管理器中获取0

 getSupportFragmentManager().getBackStackEntryCount();
 getFragmentManager().getBackStackEntryCount();

我猜它应该工作了，因为我检查了片段导航器的google代码，并且通过规范的片段事务将其添加到了堆栈中.

FragmentNavigator.java:

 if (initialNavigation || isClearTask) {
        backStackEffect = BACK_STACK_DESTINATION_ADDED;
    } else if (isSingleTopReplacement) {
        // Single Top means we only want one instance on the back stack
        if (mBackStack.size() > 1) {
            // If the Fragment to be replaced is on the FragmentManager's
            // back stack, a simple replace() isn't enough so we
            // remove it from the back stack and put our replacement
            // on the back stack in its place
            mFragmentManager.popBackStack();
            ft.addToBackStack(Integer.toString(destId));
            mIsPendingBackStackOperation = true;
        }
        backStackEffect = BACK_STACK_UNCHANGED;
    } else {
        ft.addToBackStack(Integer.toString(destId));
        mIsPendingBackStackOperation = true;
        backStackEffect = BACK_STACK_DESTINATION_ADDED;
    }
    ft.setReorderingAllowed(true);
    ft.commit();

我没有找到任何API来通过NavController或Navigator检索此信息.

谢谢

解决方案

也可能对某人有所帮助:

<fragment
                android:id="@+id/YOUR_NAVIGATION_HOST_ID"
                android:name="androidx.navigation.fragment.NavHostFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:defaultNavHost="true"
                app:navGraph="@navigation/YOUR_NAVIGATION_HOST" />

val navHostFragment = supportFragmentManager.findFragmentById(R.id.YOUR_NAVIGATION_HOST_ID)
val backStackEntryCount = navHostFragment?.childFragmentManager?.backStackEntryCount

I want to implement backpress behaviour such that it prompts a confirmation popup when you press back with the backstack empty, otherwise it pops the next fragment in the stack.

I'm trying to get the backstack count, but i always get 0 from both fragment managers

 getSupportFragmentManager().getBackStackEntryCount();
 getFragmentManager().getBackStackEntryCount();

I guess it should work since i checked the google code of fragment navigator and it adds to backstack through the canonical fragment transaction:

FragmentNavigator.java:

 if (initialNavigation || isClearTask) {
        backStackEffect = BACK_STACK_DESTINATION_ADDED;
    } else if (isSingleTopReplacement) {
        // Single Top means we only want one instance on the back stack
        if (mBackStack.size() > 1) {
            // If the Fragment to be replaced is on the FragmentManager's
            // back stack, a simple replace() isn't enough so we
            // remove it from the back stack and put our replacement
            // on the back stack in its place
            mFragmentManager.popBackStack();
            ft.addToBackStack(Integer.toString(destId));
            mIsPendingBackStackOperation = true;
        }
        backStackEffect = BACK_STACK_UNCHANGED;
    } else {
        ft.addToBackStack(Integer.toString(destId));
        mIsPendingBackStackOperation = true;
        backStackEffect = BACK_STACK_DESTINATION_ADDED;
    }
    ft.setReorderingAllowed(true);
    ft.commit();

I didn't find any API to retrieve this information through NavController or Navigator neither.

Thanks

解决方案

May be help to someone too:

<fragment
                android:id="@+id/YOUR_NAVIGATION_HOST_ID"
                android:name="androidx.navigation.fragment.NavHostFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:defaultNavHost="true"
                app:navGraph="@navigation/YOUR_NAVIGATION_HOST" />

val navHostFragment = supportFragmentManager.findFragmentById(R.id.YOUR_NAVIGATION_HOST_ID)
val backStackEntryCount = navHostFragment?.childFragmentManager?.backStackEntryCount

这篇关于使用Android导航组件获取Backstack状态的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！