Question

我知道在stackoverflow上有很多关于这方面的问题，但我认为我的问题是独一无二的。

这是我的代码：

public void emptyBackStackNow() {
    FragmentManager fragmentManager = act.getFragmentManager();


    Log.i("Fragments count on the stack: ", fragmentManager.getBackStackEntryCount() + "");
    for (int i = 0; i < fragmentManager.getBackStackEntryCount(); i++) {

        String fragmentTag = fragmentManager.getBackStackEntryAt(i).getName();
        Log.i("Fragment on the stack: ", fragmentTag);

    }

    Log.i("Fragments count on the stack, right before popping: ", fragmentManager.getBackStackEntryCount() + "");
    for (int i = 0; i < fragmentManager.getBackStackEntryCount(); i++) {

        fragmentManager.popBackStackImmediate();
        Log.i("Fragment popped from stack: ", "just popped: "+i+".");

    }

    Log.i("Fragments count on the stack after popping: ", fragmentManager.getBackStackEntryCount() + "");
    for (int i = 0; i < fragmentManager.getBackStackEntryCount(); i++) {

        String fragmentTag = fragmentManager.getBackStackEntryAt(i).getName();
        Log.i("Fragments still on the stack:", fragmentTag);

    }

}

奇怪的日志：

2-05 10:30:10.649: I/Fragments count on the stack:(25133): 14
12-05 10:30:10.649: I/Fragment on the stack:(25133): ContactFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): IdopontKeresFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): IdopontjaimFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): LeleteimFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): TeethbrushFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): MessageListFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): IdopontjaimFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): ContactFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): IdopontKeresFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): IdopontjaimFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): SegedanyagokFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): ContactFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): ASZFFragment
12-05 10:30:10.649: I/Fragment on the stack:(25133): MessageListFragment
12-05 10:30:10.649: I/Fragments count on the stack, right before popping:(25133): 14
12-05 10:30:10.729: I/Fragment popped from stack:(25133): just popped: 0.
12-05 10:30:10.739: I/Fragment popped from stack:(25133): just popped: 1.
12-05 10:30:10.739: I/Fragment popped from stack:(25133): just popped: 2.
12-05 10:30:10.749: I/Fragment popped from stack:(25133): just popped: 3.
12-05 10:30:10.749: I/Fragment popped from stack:(25133): just popped: 4.
12-05 10:30:10.779: I/Fragment popped from stack:(25133): just popped: 5.
12-05 10:30:10.789: I/Fragment popped from stack:(25133): just popped: 6.
12-05 10:30:10.789: I/Fragment popped from stack:(25133): just popped: 7.
12-05 10:30:10.789: I/Fragments counton the stack after popping:(25133): 7
12-05 10:30:10.789: I/Fragments still on the stack:(25133): ContactFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): IdopontKeresFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): IdopontjaimFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): LeleteimFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): TeethbrushFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): MessageListFragment
12-05 10:30:10.789: I/Fragments still on the stack:(25133): IdopontjaimFragment

你可以清楚地看到，第二个for循环没有迭代整个堆栈。

简单的问题：这怎么可能？

Answer 1

这是因为，当你在这个循环中弹出片段时 -

    for (int i = 0; i < fragmentManager.getBackStackEntryCount(); i++) 
    {
        fragmentManager.popBackStackImmediate();
        Log.i("Fragment popped from stack: ", "just popped: "+i+".");

    }

然后，“fragmentManager.getBackStackEntryCount（）”将返回比前一个计数少一个的总计数。要克服这个问题，你必须这样做 -

           int count = fragmentManager.getBackStackEntryCount();
           for (int i = 0; i < count; i++) 
            {
                fragmentManager.popBackStackImmediate();
                Log.i("Fragment popped from stack: ", "just popped: "+i+".");

            }

清除碎片堆栈

1 个答案: