android - 如何在fragment中实现onBackPressed并到达HomeFragment？

Question

我正在使用 3 个 fragment (HomeFragment、RegisterFragment 和 NewsFragment)。当我单击“后退”按钮时，如何从 NewsFragment 移动到直接 HomeFragment。单击后退按钮时，我不想移动到其他 fragment 。

Answer 1

我制作了一个实用程序类来控制我的 fragment 导航。

这是这个类的样子:

public class FragmentController {

    private static final String TAG = FragmentController.class.getCanonicalName();
    private static FragmentController mInstance;
    private ArrayList<BaseFragment> mFragmentsList;
    private BaseActivity mActivity;
    private FrameLayout mFragmentContainer;

    public FragmentController(BaseActivity activity) {
        set(activity);
    }

    public static FragmentController getInstance(BaseActivity activity) {
        if (mInstance == null)
            mInstance = new FragmentController(activity);
        return mInstance;
    }

    public static void setInstance(FragmentController mInstance) {
        FragmentController.mInstance = mInstance;
    }

    public void set(BaseActivity activity) {
        mActivity = activity;
        if (mActivity instanceof MainActivity) {
            mFragmentContainer = ((MainActivity) mActivity).getFragmentContainer();
        }
        mFragmentsList = new ArrayList<>();
    }

    public void addFirstFragment(BaseFragment fragment) {
        mFragmentsList.add(fragment);
    }

    public void presentFragment(BaseFragment fragment, boolean removeAllFromBackstack) {
        try {
            Log.d(TAG, "presentFragment: " + fragment.getTagFm());
            if (mActivity.getCurrentFocus() != null) {
                ViewUtils.hideKeyboard(mActivity.getCurrentFocus());
            }
            FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
            ft.setCustomAnimations(R.anim.fade_in, R.anim.fade_out);
            ft.replace(mFragmentContainer.getId(), fragment, fragment.getTagFm());
            ft.addToBackStack(fragment.getTagFm());
            ft.commitAllowingStateLoss();
            if (mFragmentsList.size() != 0)
                if (removeAllFromBackstack) {
                    if (mFragmentsList.size() == 2) {
                        mFragmentsList.remove(1);
                    } else if (mFragmentsList.size() > 2) {
                        mFragmentsList.subList(1, mFragmentsList.size()).clear();
                    }
                }
            if (!isFragmentPresent(fragment))
                mFragmentsList.add(fragment);
        } catch (Exception e) {
            e.printStackTrace();


 }
}

public void removeSecondFragment() {
    mFragmentsList.remove(1);
}

private boolean isFragmentPresent(BaseFragment fragment) {
    for (BaseFragment baseFragment : mFragmentsList) {
        if (baseFragment.getTagFm().equals(fragment.getTagFm()))
            return true;
    }
    return false;
}

public BaseFragment getCurrentFragment() {
    return mFragmentsList.get(mFragmentsList.size() - 1);
}

public ArrayList<BaseFragment> getFragmentsList() {
    return mFragmentsList;
}

现在，我在 Activity 中实例化这个类

mFragmentController = FragmentController.getInstance(this);

现在，我从我的 Activity

执行此 onBackPressed()

@Override
public void onBackPressed() {
    if (mFragmentController.getFragmentsList().size() == 1) {
        finish();
    } 
    else {
        mFragmentController.getFragmentsList().remove(mFragmentController.getFragmentsList().size() - 1);
        mFragmentController.presentFragment(mFragmentController.getFragmentsList().get(mFragmentController.getFragmentsList().size() - 1), false);
    }
}

在FragmentController 类中，您将看到我在BaseFragment 类上使用方法getTagFm()。这基本上是为了识别 que 中存在哪些 fragment ，哪些不存在。 BaseFragment 类将是这样的:

public class BaseFragment extends Fragment {

 public String getTagFm() {
        if (this.getClass().getSimpleName().equals(LoginFragment.class.getSimpleName())) {
            return Constants.TAG_FRAGMENT_LOGIN;
        } else if (this.getClass().getSimpleName().equals(OrderFragment.class.getSimpleName())) {
            return Constants.TAG_FRAGMENT_ORDER;
        } else if (this.getClass().getSimpleName().equals(ProgramFragment.class.getSimpleName())) {
            return Constants.TAG_FRAGMENT_PROGRAM;
        } 
        return Constants.TAG_FRAGMENT_ORDER;
    }

}

所有这些 fragment (LoginFragment、OrderFragment、ProgramFragment)都扩展了 BaseFragment。

希望这对某人有帮助。