Handle Retrofit todo response safely

Author: MihaiCristianCondrea

app/src/main/java/com/d4rk/androidtutorials/java/ui/screens/android/lessons/networking/retrofit/RetrofitActivity.java

@@ -5,13 +5,17 @@
 import android.os.Handler;
 import android.os.Looper;
 
+import androidx.annotation.Keep;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import com.d4rk.androidtutorials.java.R;
 import com.d4rk.androidtutorials.java.databinding.ActivityRetrofitBinding;
 import com.d4rk.androidtutorials.java.ui.components.navigation.UpNavigationActivity;
 import com.d4rk.androidtutorials.java.utils.EdgeToEdgeDelegate;
+import com.google.gson.annotations.SerializedName;
+
+import java.util.Map;
 
 import retrofit2.Call;
 import retrofit2.Callback;
@@ -47,17 +51,17 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
             api.getTodo().enqueue(new Callback<>() {
                 @Override
                 public void onResponse(@NonNull Call<Todo> call, @NonNull Response<Todo> response) {
-                    if (response.isSuccessful() && response.body() != null) {
-                        binding.textViewResult.setText(response.body().title);
+                    if (response.isSuccessful()) {
+                        displayTodoTitle(response);
                     } else {
-                        binding.textViewResult.setText(R.string.snack_general_error);
+                        showGeneralErrorMessage();
                     }
                     binding.buttonFetch.setEnabled(true);
                 }
 
                 @Override
                 public void onFailure(@NonNull Call<Todo> call, @NonNull Throwable t) {
-                    binding.textViewResult.setText(R.string.snack_general_error);
+                    showGeneralErrorMessage();
                     binding.buttonFetch.setEnabled(true);
                 }
             });
@@ -74,12 +78,37 @@ protected void onDestroy() {
         handler.removeCallbacksAndMessages(null);
     }
 
+    private void displayTodoTitle(@NonNull Response<Todo> response) {
+        Object body = response.body();
+        if (body instanceof Todo) {
+            Todo todo = (Todo) body;
+            if (todo.title != null && !todo.title.isEmpty()) {
+                binding.textViewResult.setText(todo.title);
+                return;
+            }
+        } else if (body instanceof Map<?, ?> map) {
+            Object title = map.get("title");
+            if (title != null) {
+                binding.textViewResult.setText(String.valueOf(title));
+                return;
+            }
+        }
+        showGeneralErrorMessage();
+    }
+
+    private void showGeneralErrorMessage() {
+        binding.textViewResult.setText(R.string.snack_general_error);
+    }
+
     interface JsonPlaceholderApi {
         @GET("todos/1")
         Call<Todo> getTodo();
     }
 
-    static class Todo {
+    @Keep
+    public static final class Todo {
+        @SerializedName("title")
+        @Nullable
         public String title;
     }
 }

app/src/main/res/raw/text_retrofit_java.txt

@@ -5,13 +5,17 @@ import android.os.Bundle;
 import android.os.Handler;
 import android.os.Looper;
 
+import androidx.annotation.Keep;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
+import com.d4rk.androidtutorials.java.R;
 import com.d4rk.androidtutorials.java.databinding.ActivityRetrofitBinding;
 import com.d4rk.androidtutorials.java.ui.components.navigation.UpNavigationActivity;
 import com.d4rk.androidtutorials.java.utils.EdgeToEdgeDelegate;
+import com.google.gson.annotations.SerializedName;
 
-import com.d4rk.androidtutorials.java.R;
+import java.util.Map;
 
 import retrofit2.Call;
 import retrofit2.Callback;
@@ -21,19 +25,10 @@ import retrofit2.converter.gson.GsonConverterFactory;
 import retrofit2.http.GET;
 
 public class RetrofitActivity extends UpNavigationActivity {
-    private ActivityRetrofitBinding binding;
     private final Handler handler = new Handler(Looper.getMainLooper());
+    private ActivityRetrofitBinding binding;
     private JsonPlaceholderApi api;
 
-    interface JsonPlaceholderApi {
-        @GET("todos/1")
-        Call<Todo> getTodo();
-    }
-
-    static class Todo {
-        public String title;
-    }
-
     @Override
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -50,20 +45,20 @@ public class RetrofitActivity extends UpNavigationActivity {
 
         binding.buttonFetch.setOnClickListener(v -> {
             binding.buttonFetch.setEnabled(false);
-            api.getTodo().enqueue(new Callback<Todo>() {
+            api.getTodo().enqueue(new Callback<>() {
                 @Override
-                public void onResponse(Call<Todo> call, Response<Todo> response) {
-                    if (response.isSuccessful() && response.body() != null) {
-                        binding.textViewResult.setText(response.body().title);
+                public void onResponse(@NonNull Call<Todo> call, @NonNull Response<Todo> response) {
+                    if (response.isSuccessful()) {
+                        displayTodoTitle(response);
                     } else {
-                        binding.textViewResult.setText(R.string.snack_general_error);
+                        showGeneralErrorMessage();
                     }
                     binding.buttonFetch.setEnabled(true);
                 }
 
                 @Override
-                public void onFailure(Call<Todo> call, Throwable t) {
-                    binding.textViewResult.setText(R.string.snack_general_error);
+                public void onFailure(@NonNull Call<Todo> call, @NonNull Throwable t) {
+                    showGeneralErrorMessage();
                     binding.buttonFetch.setEnabled(true);
                 }
             });
@@ -79,4 +74,38 @@ public class RetrofitActivity extends UpNavigationActivity {
         super.onDestroy();
         handler.removeCallbacksAndMessages(null);
     }
+
+    private void displayTodoTitle(@NonNull Response<Todo> response) {
+        Object body = response.body();
+        if (body instanceof Todo) {
+            Todo todo = (Todo) body;
+            if (todo.title != null && !todo.title.isEmpty()) {
+                binding.textViewResult.setText(todo.title);
+                return;
+            }
+        } else if (body instanceof Map<?, ?> map) {
+            Object title = map.get("title");
+            if (title != null) {
+                binding.textViewResult.setText(String.valueOf(title));
+                return;
+            }
+        }
+        showGeneralErrorMessage();
+    }
+
+    private void showGeneralErrorMessage() {
+        binding.textViewResult.setText(R.string.snack_general_error);
+    }
+
+    interface JsonPlaceholderApi {
+        @GET("todos/1")
+        Call<Todo> getTodo();
+    }
+
+    @Keep
+    public static final class Todo {
+        @SerializedName("title")
+        @Nullable
+        public String title;
+    }
 }