Android fragment addToBackStack不适用于抽屉导航

Question

我创建了一个 Home Activity ，其中包含带有 fragment 的 Navigation Drawer onclick。我已将 fragmentTransaction.addToBackStack(null).commit(); 包含在 fragment 事务代码中。但是它不会返回到上一页，而是关闭应用程序。

在我的 MainActivity

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    // Handle navigation view item clicks here.
    int id = item.getItemId();
    RelativeLayout mainLayout=(RelativeLayout)findViewById(R.id.mainlayout);

  if (id == R.id.nav_project) {
        ProjectFragment fragment = new ProjectFragment();
        mainLayout.removeAllViews();
        fragmentTransaction.replace(R.id.mainlayout, fragment);
        fragmentTransaction.addToBackStack(null).commit();

    } 

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

我的默认 fragment

public class ProjectFragment extends Fragment {

       @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
           View v =  inflater.inflate(R.layout.fragment_project, container, false);

            return v;
        }



}

谁能帮我解决这个问题。

Answer 1

感谢您的回复，很有帮助。基本上，您需要向堆栈添加 fragment 。

不使用replace()，而是使用fragmentTransaction 的add 方法。这将为您带来预期的效果。

简单示例:fragmentTransaction.add(R.id.mainlayout, fragment);