Question

我有一个活动。此活动检查用户是否已登录。如果已登录活动的用户显示LoginFragment。如果用户从LoginFragment登录，则显示MainFragment和MainFragment用户可以转到SettingsFragment。但是如果我按下SettingsFragment上的后退按钮，它会加载一个空白片段。

我将此方法用于“片段导航”：

public void showFragment(String fragmentName){
    Fragment fragment = null;
    boolean backstack = true;
    if (fragmentName.equals(SysKeys.MAIN_FRAGMENT)){
        fragment = new MainFragment();
    } else if (fragmentName.equals(SysKeys.LOGIN_FRAGMENT)){
        fragment = new LoginFragment();
        backstack = false;
    } else if (fragmentName.equals(SysKeys.SETTINGS_FRAGMENT)){
        fragment = new SettingsFragment();
    } else if (fragmentName.equals(SysKeys.CUSTOM_LOGIN_FRAGMENT)){
        fragment = new CustomLoginFragment();
    }

    if (fragment != null){
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.setCustomAnimations(R.anim.slide_in_from_right, R.anim.slide_out_to_left, R.anim.slide_in_from_left, R.anim.slide_out_to_right);
        fragmentTransaction.replace(R.id.main_layout, fragment, fragmentName);
        if (backstack){
            fragmentTransaction.addToBackStack(null);
        }
        fragmentTransaction.commit();
    }
}

我不想反向登录LoginFragment，但我想要其他人。我的代码或逻辑出了什么问题？

更新：现在它不显示LoginFragment如果我按下MainFragment上的后退按钮，但有时它只是重新加载MainFragment如果我按下后退按钮。这是代码：

public void showFragment(String fragmentName){
    Fragment fragment = null;
    boolean backstack = true;
    if (fragmentName.equals(SysKeys.MAIN_FRAGMENT)){
        fragment = new MainFragment();
        backstack = false;
    } else if (fragmentName.equals(SysKeys.LOGIN_FRAGMENT)){
        fragment = new LoginFragment();
        backstack = false;
    } else if (fragmentName.equals(SysKeys.SETTINGS_FRAGMENT)){
        fragment = new SettingsFragment();
    } else if (fragmentName.equals(SysKeys.CUSTOM_LOGIN_FRAGMENT)){
        fragment = new CustomLoginFragment();
    }

    if (fragment != null){
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.setCustomAnimations(R.anim.slide_in_from_right, R.anim.slide_out_to_left, R.anim.slide_in_from_left, R.anim.slide_out_to_right);
        fragmentTransaction.replace(R.id.main_layout, fragment, fragmentName);
        if (backstack){
            fragmentTransaction.addToBackStack(null);
        }
        fragmentTransaction.commit();
    }
}

Answer 1

因为每次显示片段时，您都已弹出上一个后台堆栈。你为什么要那样做？尝试删除fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
当你创建MainFragment时也设置backstack = false，所以它不会将MainFragment添加到backstack，当你从MainFragment按回来时你将完成活动希望这会有所帮助。

Android上一个片段空白屏幕

1 个答案: