实现回压 Android 碎片

Question

我陷入了困境，我需要这里的帮助。这里有很多关于这个主题的文章，但其中 none 回答了我的问题。我想在 fragments 中实现 onBackPressed() 并显示 dialog 框，显示是否退出应用程序。任何帮助将不胜感激。

LoginFragment.java

    public class LoginFragment extends Fragment {
    public static final String TAG = LoginFragment.class.getSimpleName();

    private EditText mEtEmail;
    private EditText mEtPassword;
    private Button mBtLogin;
    private TextView mTvRegister;
    private TextView mTvForgotPassword;
    private TextInputLayout mTiEmail;
    private TextInputLayout mTiPassword;
    private ProgressBar mProgressBar;

    private CompositeSubscription mSubscriptions;
    private SharedPreferences mSharedPreferences;

    @NonNull
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_login,container,false);
        mSubscriptions = new CompositeSubscription();
        initViews(view);
        initSharedPreferences();
        return view;
    }
    private void initViews(View v) {

        mEtEmail = v.findViewById(R.id.et_email);
        mEtPassword = v.findViewById(R.id.et_password);
        mBtLogin = v.findViewById(R.id.btn_login);
        mTiEmail = v.findViewById(R.id.ti_email);
        mTiPassword = v.findViewById(R.id.ti_password);
        mProgressBar = v.findViewById(R.id.progress);
        mTvRegister = v.findViewById(R.id.tv_register);
        mTvForgotPassword = v.findViewById(R.id.tv_forgot_password);

        mBtLogin.setOnClickListener(view -> login());
        mTvRegister.setOnClickListener(view -> goToRegister());
        mTvForgotPassword.setOnClickListener(view -> showDialog());
    }

    private void initSharedPreferences() {

        mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(getActivity());
    }

    private void login() {

        setError();

        String email = mEtEmail.getText().toString();
        String password = mEtPassword.getText().toString();

        int err = 0;

        if (!validateEmail(email)) {

            err++;
            mTiEmail.setError("Email should be valid !");
        }

        if (!validateFields(password)) {

            err++;
            mTiPassword.setError("Password should not be empty !");
        }

        if (err == 0) {

            loginProcess(email,password);
            mProgressBar.setVisibility(View.VISIBLE);

        } else {

            showSnackBarMessage("Enter Valid Details !");
        }
    }

    private void setError() {

        mTiEmail.setError(null);
        mTiPassword.setError(null);
    }

    private void loginProcess(String email, String password) {

        mSubscriptions.add(NetworkUtil.getRetrofit(email, password).login()
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeOn(Schedulers.io())
                .subscribe(this::handleResponse,this::handleError));
    }

    private void handleResponse(Response response) {

        mProgressBar.setVisibility(View.GONE);

        SharedPreferences.Editor editor = mSharedPreferences.edit();
        editor.putString(Constants.TOKEN,response.getToken());
        editor.putString(Constants.EMAIL,response.getMessage());
        editor.apply();

        mEtEmail.setText(null);
        mEtPassword.setText(null);

        Intent intent = new Intent(getActivity(),  HomeActivity.class);
        startActivity(intent);

    }

    private void handleError(Throwable error) {

        mProgressBar.setVisibility(View.GONE);

        if (error instanceof HttpException) {

            Gson gson = new GsonBuilder().create();

            try {

                String errorBody = ((HttpException) error).response().errorBody().string();
                Response response = gson.fromJson(errorBody,Response.class);
                showSnackBarMessage(response.getMessage());

            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {

            showSnackBarMessage("No Internet Connection!");
        }
    }

    private void showSnackBarMessage(String message) {

        if (getView() != null) {

            Snackbar.make(getView(),message,Snackbar.LENGTH_SHORT).show();
        }
    }

    private void goToRegister(){

        FragmentTransaction ft = getFragmentManager().beginTransaction();
        RegisterFragment fragment = new RegisterFragment();
        ft.replace(R.id.fragmentFrame,fragment,RegisterFragment.TAG);
        ft.addToBackStack(null).commit();
    }

    private void showDialog(){

        ResetPasswordDialog fragment = new ResetPasswordDialog();

        fragment.show(getFragmentManager(), ResetPasswordDialog.TAG);
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        mSubscriptions.unsubscribe();
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity implements ResetPasswordDialog.Listener {

    public static final String TAG = MainActivity.class.getSimpleName();
    private LoginFragment mLoginFragment;
    private ResetPasswordDialog mResetPasswordDialog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (savedInstanceState == null) {
            loadFragment();
        }
    }
    private void loadFragment() {

        if (mLoginFragment == null) {

            mLoginFragment = new LoginFragment();
        }
        getFragmentManager().beginTransaction().replace(R.id.fragmentFrame, mLoginFragment, LoginFragment.TAG).commit();
    }
    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);

        String data = intent.getData().getLastPathSegment();
        Log.d(TAG, "onNewIntent: " + data);

        mResetPasswordDialog = (ResetPasswordDialog) getFragmentManager().findFragmentByTag(ResetPasswordDialog.TAG);

        if (mResetPasswordDialog != null)
            mResetPasswordDialog.setToken(data);
    }

    @Override
    public void onPasswordReset(String message) {

        showSnackBarMessage(message);
    }

    private void showSnackBarMessage(String message) {

        Snackbar.make(findViewById(R.id.activity_main), message, Snackbar.LENGTH_SHORT).show();

    }
}

在我的 Login Fragment 中，我想显示一个对话框 "Do you want to exit the application or not"。在 Yes 上它关闭当前片段并结束 activity 否则它将保持活动状态。请帮忙！

Answer 1

你甚至可以尝试这种方式

MainActivity.java

  @Override
public void onBackPressed() {

    if (getFragmentManager() != null && getFragmentManager().getBackStackEntryCount() >= 1) {

   String fragmentTag = getFragmentManager().findFragmentById(R.id.frame_container).getTag();

   if(fragmentTag.equals(LoginFragment.getTag())){
    // show Dialog code
      }else{
            super.onBackPressed();
      }

    } else {
         super.onBackPressed();
    }
}

将此代码添加到您的主 activity 中，以便在添加登录片段并单击 backpress 时，如果片段被添加到片段事务中，则首先它会找到该片段并检查其是否标签等于登录片段标签。然后，如果两个标签都匹配，那么您可以显示退出警报对话框。

Answer 2

Android 团队已经为我们准备了一种新的方法来处理 Fragments 上按下的后退按钮，因此您应该检查一下。它被称为 OnBackPressedDispatcher。

您需要将 OnBackPressedCallback 注册到要拦截按下后退按钮的片段。你可以在 Fragment 中这样做：

     @Override
     public void onAttach(@NonNull Context context) {
         super.onAttach(context);
         OnBackPressedCallback callback = new OnBackPressedCallback(true) {
             @Override
             public void handleOnBackPressed() {
                //show exit dialog
             }
         };
         requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
     }

实现回压 Android 碎片

Implement Back Pressed In Android Fragments

java

android

android-fragments

onbackpressed