为什么getFragmentManager（）。findFragmentByTag（将String.valueOf（某个整数））不工作？ [英] Why is getFragmentManager().findFragmentByTag(String.valueOf(SOME INTEGER)) NOT working?

问题描述

我有碎片的堆栈和使用getFragmentManager试图返回在栈（）。findFragmentByTag（）方法。

I have a stack of Fragments and trying go back in the stack using getFragmentManager().findFragmentByTag() method.

这方法确实返回对象，如果称这种方式：

This method does return the object if called this way:

getFragmentManager().findFragmentByTag("3")

CountingFragment {40d68d00＃2 ID = 0x7f090000 3}

CountingFragment{40d68d00 #2 id=0x7f090000 3}

但是，如果使用的变量作为自变量，它会返回NULL：

But it will return NULL if I use the variable as an argument:

                int nextLevel = currentPositionInTheStack+1;
                getFragmentManager().findFragmentByTag(String.valueOf(nextLevel));

或

                int nextLevel = currentPositionInTheStack+1;
                String nextLevelTag = "a" + nextLevel;
                getFragmentManager().findFragmentByTag(nextLevelTag);

任何建议，为什么发生这种情况，

Any suggestions why this is happening,

感谢您提前

推荐答案

想通了如何浏览前进后退堆栈中的：

Have figured out how to navigate forward and back in the stack:

对于前进导航，如果一个碎片已经存在，使用隐藏（）和show（）方法：

for the forward navigation , if next fragment already exists , used hide() and show() methods:

        Button button = (Button)findViewById(R.id.new_fragment);
        button.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                CountingFragment currentFragment = (CountingFragment)getFragmentManager().findFragmentByTag(String.valueOf(currentPositionInTheStack));
                int nextLevel = currentPositionInTheStack+1;
                currentPositionInTheStack++;
                CountingFragment nextFragment = (CountingFragment)getFragmentManager().findFragmentByTag(String.valueOf(currentPositionInTheStack));
                if (nextFragment == null) {
                    addFragmentToStack();

                }
                else
                {
                    FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
                    fragmentTransaction.hide(currentFragment);
                    fragmentTransaction.show(nextFragment);
                    fragmentTransaction.commit();

                }

            }
        });

有关的后退导航，不得不重写onBack pressed方式：

For the back navigation , had to override onBackPressed method:

        public void onBackPressed() {
            super.onBackPressed();  
            currentPositionInTheStack--;
            Log.d("Current Position In The Stack", String.valueOf(currentPositionInTheStack));
            if (currentPositionInTheStack ==0) {
                //do smth
            } }

该片段在原来的问题是NULL，应该为null，但是，为什么它返回的对象，如果我这样做getFragmentManager（）。findFragmentByTag（3），例如，目前尚不清楚。

The Fragment in the original question was NULL and should be null, though, why it returned the Object , if I did getFragmentManager().findFragmentByTag("3"), for example, is not clear.

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