如何在安卓中将不同的回调传递给同一个函数

Question

我是安卓新手，我目前正在尝试发出凌空发布请求并从 API 获得响应。我所做的是在响应成功时调用回调。如果我从单个类调用，例如，例如MainActivity回调方法，则此回调工作正常，但如果我尝试从其他类调用，则不起作用。我试图将 volleyAPIService 中的回调参数设为通用参数，但无法成功。任何形式的帮助都是可观的。

凌空服务.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，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方法，但无法成功。

主活动.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);
}
}

我用回调volleyPost()打电话给MainActivity.java

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);
}
}

我也试着从这个班级打电话给volleyPost()。我知道参数回调的类型不匹配，并试图使回调参数成为两个类的通用参数，我找不到一种方法来做到这一点。

任何形式的帮助都是可观的，提前感谢。

Answer 1

我想建议拥有一个单独的接口类，而不是将其保留在Class或Activity内。

所以声明一个这样的接口。创建单独的文件。

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简洁的实现。

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);
}
}

现在从您的MainActivity，实现您创建的接口并覆盖回调函数，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课做同样的事情。

如果在单个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，您可以检测您在onSuccess回调中得到的 API 响应。

希望这是清楚的。请随时提出任何问题。