java如何在安卓中向同一个函数传递不同的回调

Question

我是安卓新手，目前正在尝试发出凌空发帖请求，并从API获得响应。我所做的是在响应成功时调用回调。如果我从一个类调用，比如说MainActivity回调方法，这个回调可以正常工作，但是如果我试图从其他类调用，这个回调就不起作用。我试图将volleyAPIService中的回调参数设置为泛型，但未能成功。任何形式的帮助都是值得的

截击发球。java

public class VolleyAPIService {

    public void volleyPost(final MainActivity.VolleyCallback callback, String URL, Map<String, String> param, Context context) {
        RequestQueue requestQueue = Volley.newRequestQueue(context);
        final Map<String, String> params = param;

        StringRequest stringRequest = new StringRequest(Request.Method.POST, URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        callback.onSuccess(response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                    }
                }) {
            @Override
            protected Map<String, String> getParams() {;
                return params;
            }
        };
        requestQueue.add(stringRequest);
    }
}

正如我之前所说的，我试图使volleyPost（）的第一个参数更通用，以便从任何类调用这个特定的方法，但没有成功

主要活动。java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        companyLogin("abc", "123");
    }

    public interface VolleyCallback {
        void onSuccess(String result);
    }

    public void companyLogin(String companyname, String password) {
        RequestQueue requestQueue = Volley.newRequestQueue(this);
        String URL = "http://...";
        final Map<String, String> params = new HashMap<String, String>();
        params.put("name", companyname);
        params.put("pwd", password);

        Intent volley_service = new Intent(MainActivity.this, VolleyAPIService.class);
        MainActivity.this.startService(volley_service);

        VolleyAPIService volleyAPIService = new VolleyAPIService();
        volleyAPIService.volleyPost(new VolleyCallback() {
            @Override
            public void onSuccess(String result) {
                //do stuff here
                Log.d("VOLLEY", "onSuccess: " + result);
                if (!result.isEmpty()) {
                    Intent userLoginActivity = new Intent(MainActivity.this, UserLogin.class);
                    startActivity(userLoginActivity);
                } else {
                    AlertDialog.Builder login_failed = new AlertDialog.Builder(MainActivity.this);
                    login_failed.setMessage("Login Failed, invalid credentials")
                            .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {

                                }
                            });
                    AlertDialog alert = login_failed.create();
                    alert.show();
                }
            }
        }, URL, params, MainActivity.this);
    }
}

我在MainActivity.java中使用回调调用volleyPost()

用户登录。java

public class UserLogin extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_login);

        userLogin("xyz", "456", "1")
    }

    public interface VolleyCallback {
        void onSuccess(String result);
    }

    public void userLogin(String username, String password, String id) {
        RequestQueue requestQueue = Volley.newRequestQueue(this);
        String URL = "http://...";
        final Map<String, String> params = new HashMap<String, String>();
        params.put("username", username);
        params.put("password", password);
        params.put("compId", id);

        Intent volley_service = new Intent(UserLogin.this, VolleyAPIService.class);
        UserLogin.this.startService(volley_service);

        VolleyAPIService volleyAPIService = new VolleyAPIService();
        volleyAPIService.volleyPost(new VolleyCallback() {
            @Override
            public void onSuccess(String result) {
                //do stuff here
                Log.d("VOLLEY", "onSuccess: " + result);
                if (!result.isEmpty()) {
                    Intent userLoginActivity = new Intent(UserLogin.this, HomePage.class);
                    startActivity(userLoginActivity);
                } else {
                    AlertDialog.Builder login_failed = new AlertDialog.Builder(UserLogin.this);
                    login_failed.setMessage("Login Failed, invalid credentials")
                            .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                }
                            });
                    AlertDialog alert = login_failed.create();
                    alert.show();
                }
            }
        }, URL, params, UserLogin.this);
    }
}

我也尝试从这个类中调用volleyPost()。我知道类型的参数回调不匹配，并试图使回调参数对这两个类都通用，我想不出一种方法来实现这一点

任何形式的帮助都是值得感激的，请提前感谢

Answer 1

我建议使用一个单独的接口类，而不必将其保存在Class或Activity中

所以声明一个这样的接口。创建一个单独的文件

public interface VolleyCallback {
    void onSuccess(String result);
}

然后在VolleyAPIService类中创建VolleyCallback接口的public实例，如下所示。从volleyPost方法中删除参数以实现更清晰的实现

public class VolleyAPIService {

    public VolleyCallback callback; 

    public void volleyPost(String URL, Map<String, String> param, Context context) {
        RequestQueue requestQueue = Volley.newRequestQueue(context);
        final Map<String, String> params = param;

        StringRequest stringRequest = new StringRequest(Request.Method.POST, URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        callback.onSuccess(response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                    }
                }) {
            @Override
            protected Map<String, String> getParams() {;
                return params;
            }
        };
        requestQueue.add(stringRequest);
    }
}

现在，从MainActivity开始，实现您创建的接口，并重写回调函数，如下所示

public class MainActivity extends AppCompatActivity implements VolleyCallback {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        companyLogin("abc", "123");
    }
    public interface VolleyCallback {
        void onSuccess(String result);
    }

    public void companyLogin(String companyname, String password) {
        RequestQueue requestQueue = Volley.newRequestQueue(this);
        String URL = "http://...";
        final Map<String, String> params = new HashMap<String, String>();
        params.put("name", companyname);
        params.put("pwd", password);

        Intent volley_service = new Intent(MainActivity.this, VolleyAPIService.class);
        MainActivity.this.startService(volley_service);

        VolleyAPIService volleyAPIService = new VolleyAPIService();

        // Assign the callback here to listen the response from the API service.
        volleyAPIService.callback = this; 
        volleyAPIService.volleyPost(URL, params, MainActivity.this);
    }

    @Override
    public void onSuccess(String result) {
        // Handle the success or failure here
        if (!result.isEmpty()) {
            Intent userLoginActivity = new Intent(MainActivity.this, UserLogin.class);
            startActivity(userLoginActivity);
        } else {
            AlertDialog.Builder login_failed = new AlertDialog.Builder(MainActivity.this);
            login_failed.setMessage("Login Failed, invalid credentials")
                 .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {

                     }
                 });

             AlertDialog alert = login_failed.create();
             alert.show();
        }
    }
}

对你的UserLogin类做同样的事情

如果在一个Activity或Fragment中有多个API调用，您可能希望在VolleyAPIService类中保留一个标志，并将其传递给回调函数，以便检测在onSuccess回调中得到的API响应

希望这是明确的。请随时提问