Android-在替换为另一个片段之前，如何保存片段的状态？

Question

我正在通过片段“A”调用从服务器获取数据。当我用“B”替换“A”时，在从“B”返回到“A”之后，每次都会调用片段“A”，因此每次都会生成HTTPGET。如何避免这种情况，并在活动中重用类似REORDER_to_FRONT的片段？

我正在使用此代码替换为新片段

FragmentTransaction transaction = getSupportFragmentManager()
                .beginTransaction();
transaction.replace(R.id.rl_fragment_content, newFragment,
                backStackName);
transaction.addToBackStack(backStackName);
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        transaction.commit();

当我反压时，

  Fragment fragment = null;
        fragment = getSupportFragmentManager().findFragmentByTag(
                    "some_fragment_name");
        FragmentTransaction transaction = getSupportFragmentManager()
                .beginTransaction();

        transaction.replace(R.id.rl_fragment_content, fragment);
        transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        transaction.addToBackStack("some_fragment_name");
        transaction.commit();

Answer 1

有几种方法可以做到这一点，但最简单的方法是在片段上使用添加和隐藏而不是替换。此代码（未经测试）将显示newFragment2并将newFragment1添加到背包中。在您的背包代码中将显示newFragment1并将您想要的任何内容添加到背包中

FragmentTransaction transaction = getSupportFragmentManager()
            .beginTransaction();
transaction.add(R.id.rl_fragment_content, newFragment1,
            backStackName1); //now you have an instance of newFragment1
transaction.add(R.id.rl_fragment_content, newFragment2,
            backStackName2); //now you have an instance of newFragment2
transaction.addToBackStack(backStackName1);
transaction.show(newFragment2);
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
transaction.commit();

之后

Fragment fragment = null;
fragment = getSupportFragmentManager().findFragmentByTag(
            backStackName1);
FragmentTransaction transaction = getSupportFragmentManager()
        .beginTransaction();

transaction.show(fragment)
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
transaction.addToBackStack("whatever_you_want");
transaction.commit();

注意，这将持久化视图。如果您想在屏幕旋转之间保持不变，则需要在主机活动中实现捆绑。

Answer 2

只需使用以下方法防止您的片段重新膨胀视图，

if (view != null) {
//this will prevent the fragment from re-inflating(when you come back from B) 
            ViewGroup parent = (ViewGroup) view.getParent();
            parent.removeView(view);
        } else {
//inflate the view and do what you done in onCreateView()
        }