在加载片段之前检查视图是否存在

Question

我想在加载片段之前查看视图是否存在。在我加载片段的方法中，我有以下内容：

public void loadFragment(Fragment fragment){ FragmentManager fragmentManager = Objects.requireNonNull(getActivity()).getSupportFragmentManager(); // Begin Fragment transaction. FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();// Replace the layout holder with the required Fragment object. fragmentTransaction.replace(R.id.outbound_dashboard_hourly_queued, fragment); // Commit the Fragment replace action. fragmentTransaction.commit(); }

我想要的是在加载
之前检查R.id.outbound_dashboard_hourly_queued是否存在
我该如何进行？

Answer 1

试试这个

检查是否添加了Fragment

 if (getCurrentFragment() instanceof YourFragment)

奇数片段

replaceFragment(new HomeFragment(), "YourFragment");

方法

    private void replaceFragment(Fragment fragment, String tag)
    {
        Fragment currentFragment = getCurrentFragment();
        if (currentFragment != null)
            getSupportFragmentManager().beginTransaction().remove(currentFragment).commit();

        getSupportFragmentManager().beginTransaction().add(R.id.container_main, fragment, tag).commit();
    }

    public Fragment getCurrentFragment()
    {
        FragmentManager manager = getSupportFragmentManager();
        return manager.findFragmentById(R.id.container_main);
    }

    private void popBackStack()
    {
        FragmentManager fragmentManager = getSupportFragmentManager();
        int total = fragmentManager.getBackStackEntryCount();
        for (int i = 0; i < total; i++)
        {
            fragmentManager.popBackStack();
        }

    }

Answer 2

只需执行 findViewById(R.id.outbound_dashboard_hourly_queued) 然后加载片段，如果视图不是 Null 保持 if 检查。

public void loadFragment(Fragment fragment){
    FragmentManager fragmentManager = Objects.requireNonNull(getActivity()).getSupportFragmentManager();

    // Begin Fragment transaction.
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();// Replace the layout holder with the required Fragment object.
    View yourView= findViewById(R.id.outbound_dashboard_hourly_queued);
    if(yourView!=null){
    fragmentTransaction.replace(R.id.outbound_dashboard_hourly_queued, fragment);
    // Commit the Fragment replace action.
    fragmentTransaction.commit();
  }

}

Answer 3

您可以使用FragmentManager提供的findFragmentByTag(String tag)方法来检查片段是否已经存在。

Fragment fragment = getSupportFragmentManager().findFragmentByTag(TAG);

为此，您需要使用 -

提交带有该 TAG 的片段

fragmentTransaction.replace(R.id.outbound_dashboard_hourly_queued, fragment, TAG);

Answer 4

如果计数 == 0 添加，请在替换之前遵循计数检查，否则替换您的代码必须像

public void loadFragment(Fragment fragment){
    FragmentManager fragmentManager = Objects.requireNonNull(getActivity()).getSupportFragmentManager();

    // Begin Fragment transaction.
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();// Replace the layout holder with the required Fragment object.

    if(fragmentManager.getFragments().size() == 0){
        fragmentTransaction.add(R.id.outbound_dashboard_hourly_queued, fragment).commit();
    }else {
        fragmentTransaction.replace(R.id.outbound_dashboard_hourly_queued, fragment).commit();
    }
    // Commit the Fragment replace action.

}

请试试这个并告诉我。

在加载片段之前检查视图是否存在

Checking if a view exists before loading a fragment

android

android-fragments

fragmentmanager