java - 使用 Fragment 后退按钮 android

Question

我正在处理抽屉导航和 fragment ，目前我正面临来自图像的问题考虑( donut )是 HomeFragment 类。我想要实现的是

when user navigate Fragment A(Donut) -> Fragment B(Eclair) then again navigates -> Fragment H(kitkat) and then navigates -> Fragment I(Lollipop)

和正在处理它的用户。如果用户按下后退按钮，它可能基于层次结构作为

super.onBackPressed();

As result pressing back results as Fragment I -> Fragment H -> Fragment B -> finally Fragment A.

现在我需要将用户直接导航到 fragment A，而无需转到其他 fragment 类。

我是用

实现的

public class MainActivity extends AppCompatActivity {
//initializing 
int check = 0; in MainActivity
....................
...................
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_drawer);

.................
................

 drawerList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                TextView tv = (TextView) view.findViewById(R.id.textView1);
                String aa = tv.getText().toString();
                selectItemFragment(position, aa);
            }
        });

...................
...................
private void selectItemFragment(int position, String aa) {
        Fragment fragment2;
        FragmentManager fragmentManager = getSupportFragmentManager();
        switch (position) {
            case 0:
                fragment2 = new HomeFragment();
                break;
            case 1:
                fragment2 = new GalaxyFragment();
                break;
            case 2:
                fragment2 = new ShareFragment();
                break;
            default:
                fragment2 = new HomeFragment();
                break;
        }
        check = position;
        ffragm = fragment2;
        fragmentManager.beginTransaction().replace(R.id.main_fragment_container, fragment2).addToBackStack(null).commit();
        drawerList.setItemChecked(position, true);
        setTitle(aa);
        mDrawerLayout.closeDrawer(drawerList);
    }
..........................
............................
@Override
    public void onBackPressed() {
        if (check == 0) {
            finish();
        } else {
            check = 0;
            Fragment fragment2;
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragment2 = new HomeFragment();
            fragmentManager.beginTransaction().replace(R.id.main_fragment_container, fragment2).addToBackStack(null).commit();
        }
}

我现在面临问题，考虑当用户在 Galaxyfragment 类或任何其他 fragment 类中工作时，他导航到内部的另一个 fragment 类，然后他按下后退按钮它直接导航到 fragment A。所以，这里我需要使用返回堆栈层次结构，最后到 fragment 类和完成应用程序请参见下面的代码。

public class GalaxyFragment extends Fragment {
    Context cc;
    Button Addbutton;

    public GalaxyFragment() {
        // Required empty public constructor
    }
 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.home_fragment, container, false);
        ll1design = (LinearLayout) v.findViewById(R.id.llone);
        Create_list = (Button) v.findViewById(R.id.submit);
    Addbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                display_button.setVisibility(View.VISIBLE);
                ll1design.setVisibility(View.GONE);
                String value = "";
                Bundle bundle = new Bundle();
                bundle.putString("message", "" + value);
                FragmentManager fragmentManager = getFragmentManager();
                Fragment fragment = new ShareFragment();
                fragment.setArguments(bundle);
                fragmentManager.beginTransaction().replace(R.id.main_fragment_container, fragment).addToBackStack(null).commit();
            }
        });
  return v;
    }
}

所以在这里

i need to(Achieve) use backbutton to working correctly as Galaxy2Fragment -> GalaxyFragment -> HomeFragment class.

任何人都可以给我建议如何在这些类型的情况下处理这些后退按钮 fragment 。欢迎提出建议。谢谢。

Answer 1

最简单的方法是替换这条线

fragmentManager.beginTransaction().replace(R.id.main_fragment_container, fragment2).addToBackStack(null).commit();

到

FragmentTransaction ft =fragmentManager.beginTransaction()
ft.replace(R.id.main_fragment_container, fragment2)
if(fragmentManger.findFragmentById(R.id.main_fragment_container) instanceof HomeFragment)
   ft.addToBackStack(null))
ft.commit();

如果你这样做，你不需要重写 onBackPressed。