如何从android中的非活动类调用片段

Question

我有一个登录 Fragment 和一个名为 CServerResponse 的类。

我想在CServerResponse 班级里给LoginFragment 打电话。

我该怎么做？

这是CServerResponse类代码：

public class CServerResponse {
    public static CServerResponse s_m_oServerResponse;
    public Context m_Context;

    private CServerResponse(Context m_Context) {
        this.m_Context = m_Context;
    }

    public static CServerResponse getInstance() {
        if (s_m_oServerResponse == null) {
            s_m_oServerResponse = new CServerResponse();
        }
        return s_m_oServerResponse;
    }

    public void getLoginResponse() throws JSONException {
        final Fragment activity = (Fragment) m_Context;
        if (CLoginScreen.m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Transaction Successful")) {

            CLoginScreen.m_oLoginSession.setLoginData(
                CLoginScreen.s_szResponseMobile, CLoginScreen.s_szResponsePassword);

            getActivity().getSupportFragmentManager()
                         .beginTransaction()
                         .replace(R.id.container, new CDealMainListing()).commit();

            CToastMessage.getInstance().showToast(getActivity(), "You are successfully Logged In");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Agentcode Can Not Be Empty")) {

            CToastMessage.getInstance().showToast(getActivity(), "Please Enter Valid Mobile Number");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Pin Can Not Be Empty")) {

            CToastMessage.getInstance().showToast(getActivity(), "Please Enter Password");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Invalid PIN")) {

            CToastMessage.getInstance().showToast(getActivity(), "Please enter correct Password");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Subscriber/Agent Blocked due to Wrong Attempts")) {

            CToastMessage.getInstance().showToast(getActivity(), "You are blocked as You finished your all attempt");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Connection Not Available")) {

            CToastMessage.getInstance().showToast(getActivity(), "Connection Lost ! Please Try Again");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Subscriber/Agent Not Found")) {

            CToastMessage.getInstance().showToast(getActivity(), "User not found ! Kindly Regiter before Login");

        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("OTP not verify")) {

            CToastMessage.getInstance().showToast(getActivity(), "Otp not Verify ! Kindly Generate Otp on Sign Up");
        }
    }
}

Answer 1

您需要访问需要调用片段的 Activity 的上下文。

假设您在名为 startLoginFragment(Context context) 的方法中拥有相应 Activity 的上下文。该方法的代码如下：

public void startLoginFragmemt(Context context) {
    Activity activity = (Activity) context;
    FragmentManager fragmentManager = activity.getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    LoginFragment fragment = new LoginFragment();
    fragmentTransaction.add(R.id.fragment_container, fragment);
    fragmentTransaction.commit();
}

Answer 2

如果您使用的是AppCompatActivity，则相应地转换您的context，否则您将获得 Illegel cast Exception。所以用

AppCompatActivity activity = (AppCompatActivity) context;

而不是简单的activity

Activity activity = (Activity) context;

Answer 3

您可以从 Activity 中创建 Fragment，但不应在 Activity 之外使用它们，因为它们的生命周期方法仅在附加到 Activity 时才会被调用。

如果您想在 Fragment 中操作数据，您可以创建一个 Fragment 类。从一个 Activity 构造和膨胀它，然后从另一个具有公共方法的类访问它以修改信息。

根据您的情况，您可以：

• LoginFragment: 处理 UI 元素的类
• LoginActivity: 膨胀 LoginFragment 并调用 Login 服务。
• LoginService：它处理登录服务（AsyncTask ？），当它完成后，它会向 LoginActivity 返回您需要的信息，并且 Activity 会将更新发送到最终处理信息的 Fragment。

一些代码.. 正如我在 cmets 中所说的那样，此代码可能不是很有用.. 一切都取决于您如何处理所有事情...我个人喜欢将 AsyncTask 与自定义接口一起使用，用于在任务和 UI 线程（使用它们在它们之间交换数据并触发 UI 更改）。这段代码没有向您展示这种方法，而是您应该如何（以我的拙见）组织您的流程

片段：

Class LoginFragment extends Fragment {

    private PROP1 prop1;
    private PROP2 prop2;

    private LoginFragment(){}

    public static LoginFragment createInstance( PROP1 prop1, PROP2 prop2){
        this.prop1 = prop1;
        this.prop2 = prop2;
    }

    // Fragment lifecycle methods

    // Methods used by activity to trigger changes in UI..
    // They could be setters or.. really.. whatever fits best in your flow. 
    public void changeProp1(PROP1 prop1){
         this.prop1 = prop1;
         // EDIT UI ELEMENTS.. DO WHATEVER YOU NEED TO DO..
    }
}

活动：

Class LoginActivity extends Activity { // Activity or whatever Activity class you're using.

     private LoginFragment mLoginFragment;

     @Override
     public void onCreate(){ // I don't remember the correct signature

          // Create LoginFragment
          mLoginFragmet = LoginFragment.newInstance(prop1,prop2)
          // Use FragmentManager to inflate your fragment
     }

     public void serviceInvoke(){ // I don't remember the correct signature

          // Invoke your login service. I'd use an AsyncTask and an interface implementation that allows the usage of callbacks
          // When the service is complete take the result value and pass it to the proper Fragment method
          mLoginFragment.changeProp1(theResultOfTheService);
     }
}

Answer 4

这对我有用。

 public class YOUR_CLASS extends AppCompatActivity{

    public void changeFragments(Context context, Fragment fragment, String putStringName, String putStringDescription) {

         AppCompatActivity activity = (AppCompatActivity) context;
         // Pasar datos de un fragment a otro
         Bundle datosAEnviar = new Bundle();
         datosAEnviar.putString(putStringName, putStringDescription);
         fragment.setArguments(datosAEnviar);


        activity.getSupportFragmentManager().beginTransaction().addToBackStack(null).
            replace(R.id.nav_host_fragment, fragment).commit();
    }


}