片段addToBackStack行为

Question

我在Android中面临两个关于碎片的问题。

我有一个应用程序与一个导航抽屉片段在我的主要活动。当我在这个导航抽屉上单击一个项目时，一个新的片段会加载到主活动中的“fragment_placeholder”上。很简单。

创建MainActivity时，我将在fragment_placeholder中加载“homeFragment”。这个片段有一个带有两个标签的SlidingTabLayout，每个标签加载相应的片段。这个家庭片段是我的应用程序的“主要”部分。

public class MainActivity extends ActionBarActivity {

private Toolbar mToolbar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setupDrawer();

    // Loading home fragment
    if (findViewById(R.id.fragment_placeholder) != null) {

        if (savedInstanceState != null) {
            return;
        }
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        HomeFragment homeFragment = new HomeFragment();
        homeFragment.setArguments(getIntent().getExtras());

        fragmentTransaction.replace(R.id.fragment_placeholder, homeFragment);
        fragmentTransaction.addToBackStack(null); // This is not working properly
        fragmentTransaction.commit();
    }
}

 @Override
public void itemClicked(View view, int position) {

    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

    switch(position)
    {
        // Home
        case 0:
            HomeFragment homeFragment = new HomeFragment();
            fragmentTransaction.replace(R.id.fragment_placeholder, homeFragment);
            break;

        // My account
        case 1:
            MyAccountFragment myAccountFragment = new MyAccountFragment();
            fragmentTransaction.replace(R.id.fragment_placeholder, myAccountFragment);
            break;

        // Config
        case 2:
            ConfigFragment configFragment = new ConfigFragment();
            fragmentTransaction.replace(R.id.fragment_placeholder, configFragment );
            break;

    }

    fragmentTransaction.commit();
    mDrawerLayout.closeDrawer(mDrawerListView);


}

Answer 1

我根据以下答案找到了一个解决方案https://stackoverflow.com/a/14588642/1959257

我将代码更改为：

public void onBackPressed() {
    HomeFragment homeFragment = new HomeFragment();
    displayFragment(homeFragment);
}

 private void displayFragment(Fragment pFragment) {

   // Fragment currently inside the placeholder view
   Fragment fr = (Fragment) getSupportFragmentManager()
            .findFragmentById(R.id.fragment_placeholder);

   // If this fragment is a HomeFragment, close app
   if (fr instanceof HomeFragment) {
        finish();
   }
   else {
        // Replace curretly Fragment by HomeFragment
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.fragment_placeholder, pFragment);
        ft.commit();
   }
}