Offline-Enable Your Android Application

The offline store is populated based on objects called in using OfflineODataDefiningQuery. The defining queries are located in OfflineWorkerUtil.kt, in the buildOfflineODataProvider method.

The offline store is populated based on objects called in using OfflineODataDefiningQuery. The defining queries are located in OfflineWorkerUtil.kt, in the initializeOffline method.

1. In Android Studio, on Windows, press Ctrl+N, or on a Mac, press command+O, and type OfflineOpenWorker to open OfflineOpenWorker.kt and examine the open method.

   Kotlin Copy

   override suspend fun doWork(): Result = withContext(IO) {
       ... ...
       try {
           result = suspendOpen()
           ... ...
       } finally {
           ... ...
       }
       ... ...
   }
   
   private suspend fun suspendOpen(): Result {
       try {
           OfflineWorkerUtil.offlineODataProvider?.open()
           return Result.success()
       } catch (exception: OfflineODataException) {
           ... ...
       }
   }

   The worker’s work is to call the open method of the OfflineODataProvider class to perform the open operation and pass the given callbacks through.

   The OfflineOpenWorker class is called by the open method in OfflineWorkerUtil.kt, which is called by OfflineOpenViewModel when the user logs in to the application.

   Kotlin Copy

   // In OfflineWorkerUtil.kt
   fun open(context: Context): UUID {
       ... ...
       val openRequest = OneTimeWorkRequestBuilder<OfflineOpenWorker>()
           .setConstraints(constraints)
           .build()
       ... ...
   }

   Kotlin Copy

   // In OfflineOpenViewModel.kt
   fun startOpenOffline() {
       OfflineWorkerUtil.addProgressListener(progressListener)
       _uiState.update { SyncUIState() } //reset ui state for relaunch
       val openRequestId = OfflineWorkerUtil.open(getApplication())
       ... ...
   }

2. In Android Studio, on Windows, press Ctrl+N, or on a Mac, press command+O, and type OfflineSyncWorker to open OfflineSyncWorker.kt and examine the download and upload methods.

   Kotlin Copy

   override suspend fun doWork(): Result = withContext(IO) {
       ... ...
   
       OfflineWorkerUtil.offlineODataProvider?.let { provider ->
           ... ...
           try {
               OfflineWorkerUtil.addProgressListener(progressListener)
               logger.info("Start uploading data...")
               provider.upload()
               logger.info("Start downloading data...")
               startPointForSync = progressListener.totalStepsForTwoProgresses / 2
               provider.download()
           } catch (exception: OfflineODataException) {
               ... ...
           } finally {
               ... ...
           }
       }
   
       ... ...
   }

   The worker’s work is to call the download and upload method of the OfflineODataProvider class to perform the sync operation.

   The OfflineSyncWorker class is called by the sync method in OfflineWorkerUtil.kt, which is called by EntitySetViewModel when the user wants to perform a sync. When an entity is created locally in the offline store, its primary key is left unset. This is because when the user performs an upload, the server will set the primary key for the client. An upload and a download are normally performed together because the download may return updated values from the server, such as a newly-created primary key.

   Kotlin Copy

   // In OfflineWorkerUtil.kt
   fun sync(context: Context): UUID {
       ... ...
   
       val syncRequest = OneTimeWorkRequestBuilder<OfflineSyncWorker>()
           .setConstraints(constraints)
           .build()
   
       ... ...
   }

   Kotlin Copy

   // In EntitySetViewModel.kt
   fun startSync() {
       val requestId = OfflineWorkerUtil.sync(getApplication())
       ... ...
   }

1. In Android Studio, on Windows, press Ctrl+N, or on a Mac, press command+O, and type OfflineOpenWorker to open OfflineOpenWorker.kt and examine the open method.

   Kotlin Copy

   override suspend fun doWork(): Result = withContext(IO) {
       ... ...
       OfflineWorkerUtil.offlineODataProvider?.also { provider ->
           provider.open({
               ... ...
           }, { exception ->
               ... ...
           })
       }
       ... ...
   }

   The worker’s work is to call the open method of the OfflineODataProvider class to perform the open operation and pass the given callbacks through.

   The OfflineOpenWorker class is called by the open method in OfflineWorkerUtil.kt, which is called by MainBusinessActivity when the user logs in to the application.

   Kotlin Copy

   // In OfflineWorkerUtil.kt
   @JvmStatic
   fun open(context: Context) {
       ... ...
       openRequest = OneTimeWorkRequestBuilder<OfflineOpenWorker>()
           .setConstraints(constraints)
           .build()
       ... ...
   }

   Kotlin Copy

   // In MainBusinessActivity.kt
   override fun onResume() {
       ... ...
       spforLockAndWipe.getString(SAPWizardApplication.LOCK_WIPE_INVOKING_FLAG, null)?.let {
           ... ...
       } ?: run {
           ... ...
           OfflineWorkerUtil.open(application)
           ... ...
       }
   }

2. In Android Studio, on Windows, press Ctrl+N, or on a Mac, press command+O, and type OfflineSyncWorker to open OfflineSyncWorker.kt and examine the download and upload methods.

   Kotlin Copy

   override suspend fun doWork(): Result = withContext(IO) {
       ... ...
   
       OfflineWorkerUtil.offlineODataProvider?.also { provider ->
           ... ...
           provider.upload({
               ... ...
               provider.download({
                   ... ...
               }, {
                   ... ...
               })
           }, {
               ... ...
           })
       }
   
       ... ...
   }

   The worker’s work is to call the download and upload method of the OfflineODataProvider class to perform the sync operation and pass the given callbacks through.

   The OfflineSyncWorker class is called by the sync method in OfflineWorkerUtil.kt, which is called by EntitySetListActivity when the user wants to perform a sync. When an entity is created locally in the offline store, its primary key is left unset. This is because when the user performs an upload, the server will set the primary key for the client. An upload and a download are normally performed together because the download may return updated values from the server, such as a newly-created primary key.

   Kotlin Copy

   // In OfflineWorkerUtil.kt
   @JvmStatic
   fun sync(context: Context) {
       ... ...
   
       syncRequest = OneTimeWorkRequestBuilder<OfflineSyncWorker>()
           .setConstraints(constraints)
           .build()
   
       ... ...
   }

   Kotlin Copy

   // In EntitySetListActivity.kt
   private fun synchronize() {
       OfflineWorkerUtil.sync(application)
       ... ...
   }

1. Update a SalesOrderItem and change its quantity to be zero and save it. Update a second item and change its quantity to a different non-zero number and save it.

   

   

   

   Notice that the items are now marked with a yellow indicator to indicate that an item has been locally modified but not yet synced.

   

2. Attempt a sync, and you’ll notice that the sync completes, but if you examine the SalesOrderItems list, one item has a red mark beside it, indicating it is in an error state. This is because the back end has a check that SalesOrderItems cannot have zero for their quantity. This check does not exist in the local offline store, so the update succeeds locally but fails when the offline store is synced.

   

1. Update a SalesOrderItem and change its quantity to be zero and save it. Update a second item and change its quantity to a different non-zero number and save it.

   

   

   

   Notice that the items are now marked with a yellow indicator to indicate that an item has been locally modified but not yet synced.

   

2. Attempt a sync, and you’ll notice that the sync completes, but if you examine the SalesOrderItems list, one item has a red mark beside it, indicating it is in an error state. This is because the back end has a check that SalesOrderItems cannot have zero for their quantity. This check does not exist in the local offline store, so the update succeeds locally but fails when the offline store is synced.

   

1. Press Shift twice and type strings.xml to open res\values\strings.xml.

2. Add the following values.

   XML Copy

   <string name="error_header">Error Information</string>
   <string name="request_method">Request Method</string>
   <string name="request_status">Request Status</string>
   <string name="request_message">Request Message</string>
   <string name="request_body">Request Body</string>
   <string name="request_url">Request URL</string>

3. Create a new screen in the app/kotlin+java/com.sap.wizapp/ui/odata/screens folder by right-clicking, then selecting New > Kotlin Class/File > File. Name the new file ErrorScreen.

4. Replace the ErrorScreen.kt generated code with the following code.

   In the package statement and the import, if needed, replace com.sap.wizapp with the package name of your project.

   Kotlin Copy

   package com.sap.wizapp.ui.odata.screens
   
   import androidx.compose.foundation.layout.padding
   import androidx.compose.foundation.lazy.LazyColumn
   import androidx.compose.material3.Text
   import androidx.compose.runtime.Composable
   import androidx.compose.ui.Modifier
   import androidx.compose.ui.res.stringResource
   import androidx.compose.ui.unit.dp
   import androidx.lifecycle.viewmodel.compose.viewModel
   import com.sap.cloud.mobile.fiori.compose.common.FioriDivider
   import com.sap.cloud.mobile.fiori.compose.navigation.ui.HeadlineText
   import com.sap.cloud.mobile.fiori.compose.theme.FioriTextStyleOverline
   import com.sap.cloud.mobile.fiori.compose.theme.TextAppearanceFioriSubtitle1
   import com.sap.wizapp.R
   import org.json.JSONObject
   
   const val ERROR_URL = "requestURL"
   const val ERROR_CODE = "statusCode"
   const val ERROR_METHOD = "method"
   const val ERROR_BODY = "body"
   const val ERROR_MESSAGE = "message"
   
   @Composable
   fun ErrorScreen(navigateUp: () -> Unit, errorInfo: String?) {
       // Display the error information
   
       val errorInfoJson = errorInfo?.let{ JSONObject(errorInfo) }
       val errorUrl = errorInfoJson?.getString(ERROR_URL)
       val errorCode = errorInfoJson?.getInt(ERROR_CODE)
       val errorMethod = errorInfoJson?.getString(ERROR_METHOD)
       val errorBody = errorInfoJson?.getString(ERROR_BODY)
       val errorMessage = errorInfoJson?.getString(ERROR_MESSAGE)
   
       OperationScreen(
           screenSettings = OperationScreenSettings(
               title = stringResource(id = R.string.application_name),
               navigateUp = navigateUp,
           ),
           modifier = Modifier,
           viewModel = viewModel()
       ) {
           LazyColumn {
               item {
                   HeadlineText(
                       text = stringResource(id = R.string.error_header),
                       modifier = Modifier.padding(16.dp)
                   )
                   FioriDivider()
                   Text(
                       text = stringResource(id = R.string.request_message).uppercase(),
                       modifier = Modifier.padding(16.dp),
                       style = FioriTextStyleOverline
                   )
                   Text(
                       text = errorMessage ?: stringResource(id = R.string.request_message),
                       modifier = Modifier.padding(start = 16.dp, end = 16.dp, bottom = 16.dp),
                       style = TextAppearanceFioriSubtitle1
                   )
                   FioriDivider()
                   Text(
                       text = stringResource(id = R.string.request_body).uppercase(),
                       modifier = Modifier.padding(16.dp),
                       style = FioriTextStyleOverline
                   )
                   Text(
                       text = errorBody ?: stringResource(id = R.string.request_body),
                       modifier = Modifier.padding(start = 16.dp, end = 16.dp, bottom = 16.dp),
                       style = TextAppearanceFioriSubtitle1
                   )
                   FioriDivider()
                   Text(
                       text = stringResource(id = R.string.request_url).uppercase(),
                       modifier = Modifier.padding(16.dp),
                       style = FioriTextStyleOverline
                   )
                   Text(
                       text = errorUrl ?: stringResource(id = R.string.request_url),
                       modifier = Modifier.padding(start = 16.dp, end = 16.dp, bottom = 16.dp),
                       style = TextAppearanceFioriSubtitle1
                   )
                   FioriDivider()
                   Text(
                       text = stringResource(id = R.string.request_status).uppercase(),
                       modifier = Modifier.padding(16.dp),
                       style = FioriTextStyleOverline
                   )
                   Text(
                       text = (errorCode ?: 0).toString(),
                       modifier = Modifier.padding(start = 16.dp, bottom = 16.dp),
                       style = TextAppearanceFioriSubtitle1
                   )
                   FioriDivider()
                   Text(
                       text = stringResource(id = R.string.request_method).uppercase(),
                       modifier = Modifier.padding(16.dp),
                       style = FioriTextStyleOverline
                   )
                   Text(
                       text = errorMethod ?: stringResource(id = R.string.request_method),
                       modifier = Modifier.padding(start = 16.dp, bottom = 16.dp),
                       style = TextAppearanceFioriSubtitle1
                   )
                   FioriDivider()
               }
           }
       }
   }

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5. On Windows, press Ctrl+Shift+N, or on a Mac, press command+shift+O, and type EntitySetsScreen to open EntitySetsScreen.kt.

6. Add a parameter after navigateToSettings in the EntitySetScreen function:

   Kotlin Copy

   @Composable
   fun EntitySetScreen(
       list: List<EntityScreenInfo>,
       onRowClick: (EntityType) -> Unit,
       modifier: Modifier = Modifier,
       navigateToSettings: () -> Unit,
       navigateToErrorScreen: (String) -> Unit
   ) {

7. Add the following imports:

   Kotlin Copy

   import android.util.Log
   import com.sap.cloud.mobile.kotlin.odata.offline.OfflineODataException
   import org.json.JSONException
   import org.json.JSONObject

8. Modify the EntitySetScreen in the EntitySetScreenPreview function correspondingly.

   Kotlin Copy

   @Preview
   @Composable
   fun EntitySetScreenPreview() {
       val entityTypeNames = EntityScreenInfo.entries
       EntitySetScreen(entityTypeNames, { println("click $it row") }, navigateToSettings = {}, navigateToErrorScreen = {})
   }

9. In the action tiems list of the OperationScreen, modify the action of ActionItem synchronize from viewModel::startSync to the following, which queries the error archive and displays information to the user about the first error encountered after sync finished:

   Kotlin Copy

   viewModel.startSync()
   val provider = OfflineWorkerUtil.offlineODataProvider
   
   try {
       val errorArchive = provider!!.getErrorArchive()
   
       for (errorEntity in errorArchive) {
           val requestURL = errorEntity.requestURL
           val method = errorEntity.requestMethod
           val message = errorEntity.message
           val statusCode = errorEntity.httpStatusCode ?: 0
           val body = errorEntity.requestBody
   
           Log.e("ErrorArchive", "RequestURL: $requestURL")
           Log.e("ErrorArchive", "HTTP Status Code: $statusCode")
           Log.e("ErrorArchive", "Method: $method")
           Log.e("ErrorArchive", "Message: $message")
           Log.e("ErrorArchive", "Body: $body")
   
           val finalMessage = try {
               val jsonObj = message?.let { JSONObject(it) }
               jsonObj?.let {
                   jsonObj.getJSONObject("error").getString("message")
               }
           } catch (e: JSONException) {
               e.printStackTrace()
               message
           }
   
           val errorInfo = JSONObject().apply {
                               put(ERROR_URL, requestURL)
                               put(ERROR_METHOD, method)
                               put(ERROR_MESSAGE, finalMessage)
                               put(ERROR_CODE, statusCode)
                               put(ERROR_BODY, body)
                           }
   
           // Reverts all failing entities to the previous state or set
           // offlineODataParameters.setEnableIndividualErrorArchiveDeletion(true);
           // to cause the deleteEntity call to only revert the specified entity
           // https://help.sap.com/doc/f53c64b93e5140918d676b927a3cd65b/Cloud/en-US/docs-en/guides/features/offline/common/handling-failed-requests/reverting-error-state.html
           // provider.deleteEntity(errorEntity, null, null);
           navigateToErrorScreen(errorInfo.toString())
           break //For simplicity, only show the first error encountered
       }
   } catch (e: OfflineODataException) {
       e.printStackTrace()
   }

   Show all 48 lines Show less

   After modification, the ActionItem of synchronize should look like this:

   Kotlin Copy

   ActionItem(
       nameRes = R.string.synchronize_action,
       overflowMode = OverflowMode.ALWAYS_OVERFLOW,
       doAction = {
           viewModel.startSync()
           val provider = OfflineWorkerUtil.offlineODataProvider
   
           try {
               val errorArchive = provider!!.getErrorArchive()
   
               for (errorEntity in errorArchive) {
                   val requestURL = errorEntity.requestURL
                   val method = errorEntity.requestMethod
                   val message = errorEntity.message
                   val statusCode = errorEntity.httpStatusCode ?: 0
                   val body = errorEntity.requestBody
   
                   Log.e("ErrorArchive", "RequestURL: $requestURL")
                   Log.e("ErrorArchive", "HTTP Status Code: $statusCode")
                   Log.e("ErrorArchive", "Method: $method")
                   Log.e("ErrorArchive", "Message: $message")
                   Log.e("ErrorArchive", "Body: $body")
   
                   val finalMessage = try {
                       val jsonObj = message?.let { JSONObject(it) }
                       jsonObj?.let {
                           jsonObj.getJSONObject("error").getString("message")
                       }
                   } catch (e: JSONException) {
                       e.printStackTrace()
                       message
                   }
   
                   val errorInfo = JSONObject().apply {
                                       put(ERROR_URL, requestURL)
                                       put(ERROR_METHOD, method)
                                       put(ERROR_MESSAGE, finalMessage)
                                       put(ERROR_CODE, statusCode)
                                       put(ERROR_BODY, body)
                                   }
   
                   // Reverts all failing entities to the previous state or set
                   // offlineODataParameters.setEnableIndividualErrorArchiveDeletion(true);
                   // to cause the deleteEntity call to only revert the specified entity
                   // https://help.sap.com/doc/f53c64b93e5140918d676b927a3cd65b/Cloud/en-US/docs-en/guides/features/offline/common/handling-failed-requests/reverting-error-state.html
                   // provider.deleteEntity(errorEntity, null, null);
                   navigateToErrorScreen(errorInfo.toString())
                   break //For simplicity, only show the first error encountered
               }
           } catch (e: OfflineODataException) {
               e.printStackTrace()
           }
       }
   ),

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10. On Windows, press Ctrl+Shift+N, or on a Mac, press command+shift+O, and type ODataNavHost to open ODataNavHost.kt.

11. Add the following imports:

    Kotlin Copy

    import androidx.navigation.NavType
    import androidx.navigation.navArgument

12. Add a composable component right after composable(route = EntitySetsDest.route) {} block:

    Kotlin Copy

    composable(
        route = "error/{errorInfo}",
        arguments = listOf(
            navArgument("errorInfo") { type = NavType.StringType }
        )
    ) { backStackEntry ->
        val errorInfo = backStackEntry.arguments?.getString("errorInfo")
        ErrorScreen(navController::navigateUp, errorInfo)
    }

13. Replace the composable(route = EntitySetsDest.route) {} block with the following:

    Kotlin Copy

    composable(route = EntitySetsDest.route) {
        EntitySetScreen(
            getEntitySetScreenInfoList(),
            navController::navigateToEntityList,
            navigateToSettings = { navController.navigate(SETTINGS_SCREEN_ROUTE) },
            navigateToErrorScreen = { errorInfo ->
                navController.navigate("error/${errorInfo}")
            }
        )
    }

14. Run the app again, and re-attempt the sync. When the sync fails, you should see the following error screen.

    

    You can see that the HTTP status code, method, and message are included. When the application attempted a sync, the entity being updated didn’t pass the backend checks and produced a DataServiceException and is now in the error state. All entities that did not produce errors are successfully synced. One way to correct the exception would be to change the quantity from 0 to a valid positive number. Another would be to delete the ErrorArchive entry, reverting the entity to its previous state. For more information on error handling, see Handling Errors and Conflicts and Handling Failed Requests.

1. Press Shift twice and type strings.xml to open res\values\strings.xml.

2. Add the following values.

   XML Copy

   <string name="error_header">Error Information</string>
   <string name="request_method">Request Method</string>
   <string name="request_status">Request Status</string>
   <string name="request_message">Request Message</string>
   <string name="request_body">Request Body</string>
   <string name="request_url">Request URL</string>

3. Create a new activity in the app/kotlin+java/com.sap.wizapp/mdui folder by right-clicking, then selecting New > Activity > Empty Views Activity. Name the new activity ErrorActivity.

4. Press Shift twice and type activity_error to open res/layout/activity_error.xml.

5. Replace its contents with the following XML.

   XML Copy

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto"
       xmlns:tools="http://schemas.android.com/tools"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:fitsSystemWindows="true"
       tools:context=".mdui.ErrorActivity"
       android:orientation="vertical">
   
       <com.google.android.material.appbar.AppBarLayout
           android:id="@+id/app_bar"
           android:layout_width="match_parent"
           android:layout_height="wrap_content">
   
           <androidx.appcompat.widget.Toolbar
               android:id="@+id/toolbar"
               android:layout_width="match_parent"
               android:layout_height="?attr/actionBarSize"
               app:popupTheme="@style/AppTheme.PopupOverlay"
               app:titleTextColor="@color/colorBlack" />
   
       </com.google.android.material.appbar.AppBarLayout>
   
       <ScrollView
           android:layout_height="wrap_content"
           android:layout_width="match_parent">
   
           <LinearLayout
               android:layout_height="wrap_content"
               android:layout_width="match_parent"
               android:orientation="vertical">
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/Test.ObjectCell.Headline"
                   android:text="@string/error_header"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/FioriTextStyle.OVERLINE"
                   android:text="@string/request_message"/>
   
               <TextView
                   android:id="@+id/requestMessageTextView"
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:paddingLeft="@dimen/key_line_16dp"
                   android:paddingRight="@dimen/key_line_16dp"
                   style="@style/TextAppearance.Fiori.Subtitle1"
                   android:singleLine="false"
                   android:text="@string/request_message"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/FioriTextStyle.OVERLINE"
                   android:text="@string/request_body"/>
   
               <TextView
                   android:id="@+id/requestBodyTextView"
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:paddingLeft="@dimen/key_line_16dp"
                   android:paddingRight="@dimen/key_line_16dp"
                   style="@style/TextAppearance.Fiori.Subtitle1"
                   android:singleLine="false"
                   android:text="@string/request_body"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/FioriTextStyle.OVERLINE"
                   android:text="@string/request_url"/>
   
               <TextView
                   android:id="@+id/requestURLTextView"
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:paddingLeft="@dimen/key_line_16dp"
                   android:paddingRight="@dimen/key_line_16dp"
                   style="@style/TextAppearance.Fiori.Subtitle1"
                   android:singleLine="false"
                   android:text="@string/request_url"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/FioriTextStyle.OVERLINE"
                   android:text="@string/request_status"/>
   
               <TextView
                   android:id="@+id/requestStatusTextView"
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:paddingLeft="@dimen/key_line_16dp"
                   style="@style/TextAppearance.Fiori.Subtitle1"
                   android:text="@string/request_status"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
   
               <TextView
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:padding="@dimen/key_line_16dp"
                   style="@style/FioriTextStyle.OVERLINE"
                   android:text="@string/request_method"/>
   
               <TextView
                   android:id="@+id/requestMethodTextView"
                   android:layout_width="match_parent"
                   android:layout_height="wrap_content"
                   android:paddingLeft="@dimen/key_line_16dp"
                   style="@style/TextAppearance.Fiori.Subtitle1"
                   android:text="@string/request_method"/>
   
               <View
                   android:layout_width="match_parent"
                   android:layout_marginTop="@dimen/key_line_16dp"
                   android:layout_height="1dp"
                   android:background="?android:attr/listDivider" />
           </LinearLayout>
       </ScrollView>
   </LinearLayout>

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6. Replace the ErrorActivity.kt generated activity code with the following code.

   In the package statement and the import, if needed, replace com.sap.wizapp with the package name of your project.

   Kotlin Copy

   package com.sap.wizapp.mdui
   
   import androidx.appcompat.app.AppCompatActivity
   import android.os.Bundle
   import android.view.MenuItem
   import android.view.View
   import android.widget.TextView
   
   import com.sap.wizapp.R
   
   class ErrorActivity : AppCompatActivity() {
   
       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
           setContentView(R.layout.activity_error)
           setSupportActionBar(findViewById(R.id.toolbar))
           supportActionBar!!.setDisplayHomeAsUpEnabled(true)
           val errorCode = intent.getIntExtra("ERROR_CODE", 0)
           val errorMethod = intent.getStringExtra("ERROR_METHOD")
           val requestURL = intent.getStringExtra("ERROR_URL")
           val errorMessage = intent.getStringExtra("ERROR_MESSAGE")
           val body = intent.getStringExtra("ERROR_BODY")
           (findViewById<View>(R.id.requestStatusTextView) as TextView).text = "".plus(errorCode)
   
           errorMethod?.let {
               (findViewById<View>(R.id.requestMethodTextView) as TextView).text = it
           }
           requestURL?.let {
               (findViewById<View>(R.id.requestURLTextView) as TextView).text = it
           }
           errorMessage?.let {
               (findViewById<View>(R.id.requestMessageTextView) as TextView).text = it
           }
           body?.let {
               (findViewById<View>(R.id.requestBodyTextView) as TextView).text = it
           }
       }
   
       override fun onOptionsItemSelected(item: MenuItem): Boolean {
           finish()
           return super.onOptionsItemSelected(item)
       }
   }

   Show all 43 lines Show less

7. On Windows, press Ctrl+N, or, on a Mac, press command+O, and type EntitySetListActivity to open EntitySetListActivity.kt.

8. In the updateProgressForSync method, in the WorkInfo.State.SUCCEEDED block, add the following code, which queries the error archive and displays information to the user about the first error encountered:

   Kotlin Copy

   val provider = OfflineWorkerUtil.offlineODataProvider
   
   try {
       val errorArchive = provider!!.errorArchive
   
       for (errorEntity in errorArchive) {
           val requestURL = errorEntity.requestURL
           val method = errorEntity.requestMethod
           val message = errorEntity.message
           val statusCode = errorEntity.httpStatusCode ?: 0
           val body = errorEntity.requestBody
   
           LOGGER.error("RequestURL: $requestURL")
           LOGGER.error("HTTP Status Code: $statusCode")
           LOGGER.error("Method: $method")
           LOGGER.error("Message: $message")
           LOGGER.error("Body: $body")
   
           val errorIntent = Intent(this@EntitySetListActivity, ErrorActivity::class.java)
   
           errorIntent.putExtra("ERROR_URL", requestURL)
           errorIntent.putExtra("ERROR_CODE", statusCode)
           errorIntent.putExtra("ERROR_METHOD", method)
           errorIntent.putExtra("ERROR_BODY", body)
   
           try {
               val jsonObj = message?.let { JSONObject(it) }
               jsonObj?.let {
                   errorIntent.putExtra(
                       "ERROR_MESSAGE",
                       jsonObj.getJSONObject("error").getString("message")
                   )
               }
           } catch (e: JSONException) {
               e.printStackTrace()
           }
   
           // Reverts all failing entities to the previous state or set
           // offlineODataParameters.setEnableIndividualErrorArchiveDeletion(true);
           // to cause the deleteEntity call to only revert the specified entity
           // https://help.sap.com/doc/f53c64b93e5140918d676b927a3cd65b/Cloud/en-US/docs-en/guides/features/offline/common/handling-failed-requests/reverting-error-state.html
           // provider.deleteEntity(errorEntity, null, null);
           startActivity(errorIntent)
           break //For simplicity, only show the first error encountered
       }
   } catch (e: OfflineODataException) {
       e.printStackTrace()
   }

   Show all 48 lines Show less

   After modification, the WorkInfo.State.SUCCEEDED block should look like this:

   Kotlin Copy

   WorkInfo.State.SUCCEEDED -> {
       LOGGER.info("Offline sync done.")
       val provider = OfflineWorkerUtil.offlineODataProvider
   
       try {
           val errorArchive = provider!!.errorArchive
   
           for (errorEntity in errorArchive) {
               val requestURL = errorEntity.requestURL
               val method = errorEntity.requestMethod
               val message = errorEntity.message
               val statusCode = errorEntity.httpStatusCode ?: 0
               val body = errorEntity.requestBody
   
               LOGGER.error("RequestURL: $requestURL")
               LOGGER.error("HTTP Status Code: $statusCode")
               LOGGER.error("Method: $method")
               LOGGER.error("Message: $message")
               LOGGER.error("Body: $body")
   
               val errorIntent = Intent(this@EntitySetListActivity, ErrorActivity::class.java)
   
               errorIntent.putExtra("ERROR_URL", requestURL)
               errorIntent.putExtra("ERROR_CODE", statusCode)
               errorIntent.putExtra("ERROR_METHOD", method)
               errorIntent.putExtra("ERROR_BODY", body)
   
               try {
                   val jsonObj = message?.let { JSONObject(it) }
                   jsonObj?.let {
                       errorIntent.putExtra(
                           "ERROR_MESSAGE",
                           jsonObj.getJSONObject("error").getString("message")
                       )
                   }
               } catch (e: JSONException) {
                   e.printStackTrace()
               }
   
               // Reverts all failing entities to the previous state or set
               // offlineODataParameters.setEnableIndividualErrorArchiveDeletion(true);
               // to cause the deleteEntity call to only revert the specified entity
               // https://help.sap.com/doc/f53c64b93e5140918d676b927a3cd65b/Cloud/en-US/docs-en/guides/features/offline/common/handling-failed-requests/reverting-error-state.html
               // provider.deleteEntity(errorEntity, null, null);
               startActivity(errorIntent)
               break //For simplicity, only show the first error encountered
           }
       } catch (e: OfflineODataException) {
           e.printStackTrace()
       }
   }

   Show all 51 lines Show less

9. Run the app again, and re-attempt the sync. When the sync fails, you should see the following error screen.

   

   You can see that the HTTP status code, method, and message are included. When the application attempted a sync, the entity being updated didn’t pass the backend checks and produced a DataServiceException and is now in the error state. All entities that did not produce errors are successfully synced. One way to correct the exception would be to change the quantity from 0 to a valid positive number. Another would be to delete the ErrorArchive entry, reverting the entity to its previous state. For more information on error handling, see Handling Errors and Conflicts and Handling Failed Requests.