[ADDED] Error handling for the resources section

Author: hossain-khan

app/src/main/java/com/hossainkhan/android/demo/data/ResourceResult.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2019 Hossain Khan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hossainkhan.android.demo.data
+
+
+/**
+ * A class to represent external resource request with data or error on fail.
+ */
+class ResourceResult(
+        val resources: List<ResourceInfo> = emptyList(),
+        val error: Exception? = null
+)

app/src/main/java/com/hossainkhan/android/demo/ui/resource/LearningResourceActivity.kt

@@ -21,11 +21,13 @@ import android.content.Intent
 import android.net.Uri
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
+import androidx.constraintlayout.widget.ConstraintLayout
 import androidx.databinding.DataBindingUtil
 import androidx.lifecycle.Observer
 import androidx.lifecycle.ViewModelProvider
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.snackbar.Snackbar
 import com.hossainkhan.android.demo.R
 import com.hossainkhan.android.demo.data.ResourceInfo
 import com.hossainkhan.android.demo.databinding.ActivityLearningResourceBinding
@@ -34,6 +36,9 @@ import dagger.android.AndroidInjection
 import timber.log.Timber
 import javax.inject.Inject
 
+/**
+ * This activity lists external resources on [ConstraintLayout], such as tech talks on youtube.
+ */
 class LearningResourceActivity : AppCompatActivity() {
 
     @Inject
@@ -69,7 +74,13 @@ class LearningResourceActivity : AppCompatActivity() {
         }
 
         viewModel.data.observe(this, Observer { result ->
-            ideaListAdapter.submitList(result)
+            if (result?.error != null) {
+                Timber.w(result.error, "Unable to load resources.")
+                Snackbar.make(binding.root, R.string.message_resource_load_failed, Snackbar.LENGTH_INDEFINITE).show()
+                return@Observer
+            } else {
+                ideaListAdapter.submitList(result.resources)
+            }
         })
     }
 

app/src/main/java/com/hossainkhan/android/demo/ui/resource/LearningResourceViewModel.kt

@@ -24,9 +24,10 @@ import com.google.firebase.firestore.FirebaseFirestore
 import com.google.firebase.firestore.Query
 import com.google.firebase.firestore.QuerySnapshot
 import com.hossainkhan.android.demo.data.ResourceInfo
+import com.hossainkhan.android.demo.data.ResourceResult
 import timber.log.Timber
-import java.lang.Exception
 import javax.inject.Inject
+import kotlin.Exception
 
 class LearningResourceViewModel @Inject constructor(
         firestore: FirebaseFirestore
@@ -37,8 +38,8 @@ class LearningResourceViewModel @Inject constructor(
 
     val isLoading = ObservableField(true)
 
-    private val _data = MutableLiveData<List<ResourceInfo>>()
-    val data: LiveData<List<ResourceInfo>> = _data
+    private val _data = MutableLiveData<ResourceResult>()
+    val data: LiveData<ResourceResult> = _data
 
     private val resourceData = mutableListOf<ResourceInfo>()
 
@@ -49,6 +50,12 @@ class LearningResourceViewModel @Inject constructor(
                 .get()
                 .addOnSuccessListener(this::updateResources)
                 .addOnFailureListener(this::onLoadFailed)
+                .addOnCompleteListener {
+                    if (it.result?.isEmpty == true) {
+                        Timber.i("Completed with no data. This is likely due to no internet.")
+                        onLoadFailed(Exception("No data"))
+                    }
+                }
     }
 
     private fun updateResources(result: QuerySnapshot) {
@@ -58,11 +65,12 @@ class LearningResourceViewModel @Inject constructor(
             resourceData.add(x)
         }
         isLoading.set(false)
-        _data.value = resourceData
+        _data.value = ResourceResult(resourceData)
     }
 
     private fun onLoadFailed(exception: Exception) {
         Timber.w(exception, "Error getting documents.")
         isLoading.set(false)
+        _data.value = ResourceResult(error = exception)
     }
 }

app/src/main/res/values/dimens.xml

@@ -24,7 +24,13 @@
       - https://developer.android.com/guide/topics/resources/providing-resources
       - https://developer.android.com/training/multiscreen/screensizes
 -->
-<resources>
+<resources xmlns:tools="http://schemas.android.com/tools">
+    <!--
+        Overrides snackbar text truncation.
+        https://stackoverflow.com/questions/32228300/how-to-prevent-my-snackbar-text-from-being-truncated-on-android/32228529
+    -->
+    <integer tools:override="true" name="design_snackbar_text_max_lines">4</integer>
+
     <dimen name="box_size_small">40dp</dimen>
     <dimen name="box_size_medium">80dp</dimen>
     <dimen name="box_size_large">120dp</dimen>

app/src/main/res/values/strings.xml

@@ -26,5 +26,5 @@
     <string name="additional_resource_title">External Resources</string>
     <string name="tech_talk_author_and_venue">by %1$s at %2$s</string>
     <string name="tech_talk_publish_date">Published on %1$s</string>
-
+    <string name="message_resource_load_failed">Unable to load external resources. This is likely due to no internet connectivity. Please try re-loading this screen with network connection.</string>
 </resources>