Android 中的 popBackStack 和 addToBackStack

Question

我是 android 的新手，尝试将我的 iphone 应用程序转换为 android。我尝试在片段之间导航，在从片段 A 导航到 B 之后，我想使用后退按钮从片段 B 返回到 A。我做了一个研究，但不能很好地理解它。在代码下方，我有一个导航抽屉，我可以在其中在片段之间导航。单击关注者后，我想使用后退按钮返回新闻提要。

//this is the navigation drawer part     
if (id == R.id.my_archive_drawer) {

                myArchiveFragment fragment = new myArchiveFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.addToBackStack("newsFeedFragment");
                fragmentTransaction.commit();

            } else if (id == R.id.followers_drawer) {

                followedFollowersFragment fragment = new followedFollowersFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.addToBackStack("newsFeedFragment");
                fragmentTransaction.commit();

            } 
//this is the navigation drawer part   



//this is the on create part part   
        newsFeedFragment fragment = new newsFeedFragment();
        android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container, fragment);
        fragmentTransaction.commit();
//this is the on create part part  


//onbackpreseed part
   public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            getFragmentManager().popBackStack("newsFeedFragment");
        }
    }
//onbackpressed part

Answer 1

addToBackStack的意思是把fragment放入栈中。这意味着当您将片段新闻推送给片段关注者时，您正在将片段添加到堆栈中。因此，当您返回时 return 到新闻片段。

试试这个代码：

followedFollowersFragment fragment = new followedFollowersFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();

然后在您的 onBackPressed() 中删除 popbackstack()，因为当您调用 onBackPressed 单击后退按钮时，您已经删除了关注者片段。所以 onBackPressed() 应该是这样的：

 @Override
 public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

有关这 2 种方法的更多信息，您可以阅读 here

Android 中的 popBackStack 和 addToBackStack

popBackStack and addToBackStack in Android

android

android-fragments

fragment-backstack