diff --git a/app/src/main/java/com/example/tampopo_client/models/Activity.java b/app/src/main/java/com/example/tampopo_client/models/Activity.java
new file mode 100644
index 0000000..7c3d626
--- /dev/null
+++ b/app/src/main/java/com/example/tampopo_client/models/Activity.java
@@ -0,0 +1,47 @@
+package com.example.tampopo_client.models;
+
+public class Activity {
+    private String userId;
+    private String activityId;
+    private String text;
+    private String updateTime;
+
+    public Activity(String userId, String activityId, String text, String updateTime) {
+        this.userId = userId;
+        this.activityId = activityId;
+        this.text = text;
+        this.updateTime = updateTime;
+    }
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+    }
+
+    public String getActivityId() {
+        return activityId;
+    }
+
+    public void setActivityId(String activityId) {
+        this.activityId = activityId;
+    }
+
+    public String getText() {
+        return text;
+    }
+
+    public void setText(String text) {
+        this.text = text;
+    }
+
+    public String getUpdateTime() {
+        return updateTime;
+    }
+
+    public void setUpdateTime(String updateTime) {
+        this.updateTime = updateTime;
+    }
+}
diff --git a/app/src/main/java/com/example/tampopo_client/resources/ActivitiesResource.java b/app/src/main/java/com/example/tampopo_client/resources/ActivitiesResource.java
new file mode 100644
index 0000000..7df8292
--- /dev/null
+++ b/app/src/main/java/com/example/tampopo_client/resources/ActivitiesResource.java
@@ -0,0 +1,38 @@
+package com.example.tampopo_client.resources;
+
+import com.example.tampopo_client.models.Activity;
+
+import java.util.List;
+
+import retrofit2.Call;
+import retrofit2.http.DELETE;
+import retrofit2.http.Field;
+import retrofit2.http.FormUrlEncoded;
+import retrofit2.http.GET;
+import retrofit2.http.POST;
+import retrofit2.http.Path;
+import retrofit2.http.Query;
+
+public interface ActivitiesResource {
+    @GET("users/{user_id}/activities")
+    Call<List<Activity>> getActivities(@Path("user_id") String userId, @Query("filter") String filter);
+
+    @POST("users/{user_id}/activities")
+    @FormUrlEncoded
+    Call<String> addActivity(@Path("user_id") String userId, @Field("token") String token, @Field("new-activity") String newActivity); // FIXME: We need to rename new-activity to new_activity
+
+    @GET("users/{user_id}/activities/{activity_id}")
+    Call<Activity> getActivity(@Path("user_id") String userId, @Path("activity_id") String activityId);
+
+    @DELETE("users/{user_id}/activities/{activity_id}")
+    Call<Activity> deleteActivity(@Path("user_id") String userId, @Path("activity_id") String activityId, @Query("token") String token);
+
+    @GET("users/{user_id}/activities/{activity_id}/text")
+    Call<String> getText(@Path("user_id") String userId, @Path("activity_id") String activityId);
+
+    @GET("users/{user_id}/activities/{activity_id}/updated-time")
+    Call<Activity> getUpdatedTime(@Path("user_id") String userId, @Path("activity_id") String activityId);
+
+    @GET("users/{user_id}/activities/last-updated-time")
+    Call<Activity> getLastUpdatedTime(@Path("user_id") String userId, @Path("activity_id") String activityId);
+}
diff --git a/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
new file mode 100644
index 0000000..2f7d914
--- /dev/null
+++ b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
@@ -0,0 +1,21 @@
+package com.example.tampopo_client.viewmodels;
+
+import androidx.lifecycle.ViewModel;
+
+import com.example.tampopo_client.resources.ActivitiesResource;
+
+import retrofit2.Retrofit;
+import retrofit2.converter.jackson.JacksonConverterFactory;
+
+public class ActivityViewModel extends ViewModel {
+    private final Retrofit retrofit;
+    private final ActivitiesResource activitiesResource;
+
+    public ActivityViewModel() {
+        retrofit = new Retrofit.Builder()
+                .baseUrl("http://nitta-lab-www.is.konan-u.ac.jp/tampopo-server/")
+                .addConverterFactory(JacksonConverterFactory.create())
+                .build();
+        activitiesResource = retrofit.create(ActivitiesResource.class);
+    }
+}