Android Fragment背堆栈问题该怎么解决？
Android Fragment背堆栈问题该怎么解决？
提问于 2018-03-19 10:56:57
这里是我主要活动的布局xml文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
android:id="@+id/headerFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
class="com.fragment_test.FragmentControls" >
<!-- Preview: layout=@layout/details -->
</fragment>
<FrameLayout
android:id="@+id/detailFragment"
android:layout_width="match_parent"
android:layout_height="fill_parent"
/>
这是我用来通过nav heirarchy构建的代码：
Fragment frag;
FragmentTransaction transaction;
//Create The first fragment [1], add it to the view, BUT Dont add the transaction to the backstack
frag = new Fragment1();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.commit();
//Create the second [2] fragment, add it to the view and add the transaction that replaces the first fragment to the backstack
frag = new Fragment2();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.addToBackStack(null);
transaction.commit();
//Create third fragment, Dont add this transaction to the backstack, because we dont want to go back to [2]
frag = new Fragment3();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.commit();
//END OF SETUP CODE-------------------------
//NOW:
//Press back once and then issue the following code:
frag = new Fragment2();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.addToBackStack(null);
transaction.commit();
//Now press back again and you end up at fragment [3] not [1]
回答 2
Stack Overflow用户
发布于 2018-03-19 19:09:41
如果我们记住，这.replace()与.remove().add()我们在文档中所知道的相同：
替换已添加到容器的现有片段。这与调用
remove(Fragment)当前添加的所有片段相同containerViewId，然后add(int, Fragment, String)使用与此处给出的相同参数相同。
那么发生的事情就是这样：
// transaction.replace(R.id.detailFragment, frag1);
Transaction.remove(null).add(frag1) // frag1 on view
// transaction.replace(R.id.detailFragment, frag2).addToBackStack(null);
Transaction.remove(frag1).add(frag2).addToBackStack(null) // frag2 on view
// transaction.replace(R.id.detailFragment, frag3);
Transaction.remove(frag2).add(frag3) // frag3 on view
请记住，.addToBackStack()只保存事务而不是片段本身！所以现在我们frag3在布局上：
< press back button >
// System pops the back stack and find the following saved back entry to be reversed:
// [Transaction.remove(frag1).add(frag2)]
// so the system makes that transaction backward!!!
// tries to remove frag2 (is not there, so it ignores) and re-add(frag1)
// make notice that system doesn't realise that there's a frag3 and does nothing with it
// so it still there attached to view
Transaction.remove(null).add(frag1) //frag1, frag3 on view (OVERLAPPING)
// transaction.replace(R.id.detailFragment, frag2).addToBackStack(null);
Transaction.remove(frag3).add(frag2).addToBackStack(null) //frag2 on view
< press back button >
// system makes saved transaction backward
Transaction.remove(frag2).add(frag3) //frag3 on view
< press back button >
// no more entries in BackStack
< app exits >
Stack Overflow用户
发布于 2018-03-19 20:34:37
接下来的部分是覆盖onKeyDown方法，并在每次按下后退按钮时删除当前片段：
@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK)
{
if (getSupportFragmentManager().getBackStackEntryCount() == 0)
{
this.finish();
return false;
}
else
{
getSupportFragmentManager().popBackStack();
removeCurrentFragment();
return false;
}
}
return super.onKeyDown(keyCode, event);
}
public void removeCurrentFragment()
{
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
Fragment currentFrag = getSupportFragmentManager().findFragmentById(R.id.detailFragment);
String fragName = "NONE";
if (currentFrag!=null)
fragName = currentFrag.getClass().getSimpleName();
if (currentFrag != null)
transaction.remove(currentFrag);
transaction.commit();
}
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100007676
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