Caching of data for 1 day & error handling

Author: Kishan Kumar Maurya

.idea/vcs.xml

@@ -28,6 +28,10 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+    // For Kotlin projects
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
 }
 
 dependencies {

app/build.gradle

@@ -4,5 +4,7 @@ class ApiConstant {
 
     companion object{
         const val GITHUB_BASE_URL = "https://api.github.com/repos/firebase/firebase-ios-sdk/"
+        const val HEADER_CACHE_CONTROL = "Cache-Control"
+        const val HEADER_PRAGMA = "Pragma"
     }
 }

app/src/main/java/com/example/githubfirebaseissue/api/ApiConstant.kt

@@ -11,6 +11,8 @@ import android.widget.Toast
 import androidx.fragment.app.Fragment
 import com.example.githubfirebaseissue.R
 import dagger.android.support.AndroidSupportInjection
+import okio.IOException
+import retrofit2.HttpException
 
 
 abstract class BaseFragment : Fragment() {
@@ -55,6 +57,19 @@ abstract class BaseFragment : Fragment() {
         dialog.show()
     }
 
+    protected fun handleError(th: Throwable) {
+        val error = when (th) {
+            is HttpException -> when (th.code()) {
+                401 -> getString(R.string.error_unauthorized)
+                500 -> getString(R.string.error_server)
+                else -> getString(R.string.error_server)
+            }
+            is IOException -> getString(R.string.internet_error)
+            else -> getString(R.string.error_server)
+        }
+        onError(error)
+    }
+
     /**
      * This method is called after view has been created.
      * This method should be used to initialize all views that are needed to be created (and recreated after fragment is reattached)
@@ -64,6 +79,6 @@ abstract class BaseFragment : Fragment() {
 
     abstract fun getLayoutRes(): Int
     abstract fun showLoadingState(loading: Boolean)
-    abstract fun onError(th: Throwable)
+    abstract fun onError(message: String)
 
 }

app/src/main/java/com/example/githubfirebaseissue/base/BaseFragment.kt

@@ -1,27 +1,95 @@
 package com.example.githubfirebaseissue.di.module
 
+import android.util.Log
+import com.example.githubfirebaseissue.GithubApplication
+import com.example.githubfirebaseissue.api.ApiConstant.Companion.HEADER_CACHE_CONTROL
+import com.example.githubfirebaseissue.api.ApiConstant.Companion.HEADER_PRAGMA
 import com.example.githubfirebaseissue.di.scope.AppScope
 import dagger.Module
 import dagger.Provides
-import okhttp3.OkHttpClient
+import okhttp3.*
 import okhttp3.logging.HttpLoggingInterceptor
+import java.io.File
+import okhttp3.CacheControl
+import com.example.githubfirebaseissue.helper.ApplicationUtil
+import java.util.concurrent.TimeUnit
+
 
 @Module
 class InterceptorModule {
 
     @Provides
     @AppScope
-    fun provideOkHttpClient(interceptor: HttpLoggingInterceptor): OkHttpClient {
+    fun provideOkHttpClient(
+        context: GithubApplication,
+        interceptor: HttpLoggingInterceptor
+    ): OkHttpClient {
         return OkHttpClient.Builder()
             .addInterceptor(interceptor)
+            .addInterceptor { provideOfflineCacheInterceptor(context, it) }
+            .addNetworkInterceptor { provideCacheInterceptor(context, it) }
+            .cache(provideCache(context))
             .build()
     }
 
+
     @Provides
     @AppScope
     fun provideLoggingInterceptor(): HttpLoggingInterceptor {
         val httpLoggingInterceptor = HttpLoggingInterceptor()
         httpLoggingInterceptor.level = HttpLoggingInterceptor.Level.BODY
         return httpLoggingInterceptor
     }
+
+
+    private fun provideCache(context: GithubApplication): Cache? {
+        var cache: Cache? = null
+        try {
+            cache = Cache(File(context.cacheDir, "http-cache"), 10 * 1024 * 1024)
+        } catch (e: Exception) {
+            Log.e("Cache", "Could not create Cache!")
+        }
+        return cache
+    }
+
+    private fun provideOfflineCacheInterceptor(
+        context: GithubApplication,
+        chain: Interceptor.Chain
+    ): Response {
+        var request = chain.request()
+
+        if (!ApplicationUtil.hasNetwork(context)) {
+            val cacheControl = CacheControl.Builder()
+                .maxStale(1, TimeUnit.DAYS)
+                .build()
+
+            request = request.newBuilder()
+                .removeHeader(HEADER_PRAGMA)
+                .removeHeader(HEADER_CACHE_CONTROL)
+                .cacheControl(cacheControl)
+                .build()
+        }
+
+        return chain.proceed(request)
+    }
+
+    private fun provideCacheInterceptor(
+        context: GithubApplication,
+        chain: Interceptor.Chain
+    ): Response {
+        val response = chain.proceed(chain.request())
+        val cacheControl: CacheControl = if (ApplicationUtil.hasNetwork(context)) {
+            CacheControl.Builder().maxAge(0, TimeUnit.SECONDS).build()
+        } else {
+            CacheControl.Builder()
+                .maxStale(1, TimeUnit.DAYS)
+                .build()
+        }
+
+        return response.newBuilder()
+            .removeHeader(HEADER_PRAGMA)
+            .removeHeader(HEADER_CACHE_CONTROL)
+            .header(HEADER_CACHE_CONTROL, cacheControl.toString())
+            .build()
+    }
 }

app/src/main/java/com/example/githubfirebaseissue/di/module/InterceptorModule.kt

@@ -37,7 +37,7 @@ abstract class AbstractCommentsFragment : BaseFragment() {
 
     private fun observeDataChange() {
         viewModel.loadingState.observe(viewLifecycleOwner, Observer { showLoadingState(it) })
-        viewModel.apiError.observe(viewLifecycleOwner, EventObserver { onError(it) })
+        viewModel.apiError.observe(viewLifecycleOwner, EventObserver { handleError(it) })
         viewModel.commentsLiveData.observe(viewLifecycleOwner, EventObserver {
             if (it.isNotEmpty())
                 setCommentsData(it)

app/src/main/java/com/example/githubfirebaseissue/ui/fragment/AbstractCommentsFragment.kt

@@ -24,10 +24,7 @@ abstract class AbstractIssueFragment : BaseFragment() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        if (ApplicationUtil.hasNetwork(context!!))
-            viewModel.fetchFireBaseIosIssueList()
-        else
-            showNetworkError()
+        viewModel.fetchFireBaseIosIssueList()
     }
 
     override fun viewInitialization(view: View) {
@@ -37,14 +34,13 @@ abstract class AbstractIssueFragment : BaseFragment() {
 
     private fun observeDataChange() {
         viewModel.loadingState.observe(viewLifecycleOwner, Observer { showLoadingState(it) })
-        viewModel.apiError.observe(viewLifecycleOwner, EventObserver { onError(it) })
+        viewModel.apiError.observe(viewLifecycleOwner, EventObserver { handleError(it) })
         viewModel.issueLiveData.observe(viewLifecycleOwner, EventObserver {
             setIssuesData(it)
         })
     }
 
 
     abstract fun setIssuesData(list: List<Issue>)
-    abstract fun showNetworkError()
 
 }

app/src/main/java/com/example/githubfirebaseissue/ui/fragment/AbstractIssueFragment.kt

@@ -60,8 +60,8 @@ class CommentsFragment : AbstractCommentsFragment() {
             progress.visibility = View.GONE
     }
 
-    override fun onError(th: Throwable) {
-        th.message?.let { showToast(it) }
+    override fun onError(message: String) {
+        showToast(message)
     }
 
 }

app/src/main/java/com/example/githubfirebaseissue/ui/fragment/CommentsFragment.kt

@@ -58,8 +58,8 @@ class IssuesFragment : AbstractIssueFragment(), IAdapterCallback {
             progress.visibility = View.GONE
     }
 
-    override fun onError(th: Throwable) {
-        th.message?.let { showToast(it) }
+    override fun onError(message: String) {
+        showToast(message)
     }
 
 
@@ -70,7 +70,4 @@ class IssuesFragment : AbstractIssueFragment(), IAdapterCallback {
         )
     }
 
-    override fun showNetworkError() {
-        showErrorDialog(getString(R.string.internet_error),getString(R.string.close))
-    }
 }

app/src/main/java/com/example/githubfirebaseissue/ui/fragment/IssuesFragment.kt

@@ -4,4 +4,6 @@
     <string name="go_back">Go Back</string>
     <string name="internet_error">Please check Internet</string>
     <string name="close">Close</string>
+    <string name="error_unauthorized">User Not Authorised</string>
+    <string name="error_server">Something went wrong. Please try later</string>
 </resources>