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Offline-Enable Your Android Application
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Offline-Enable Your Android Application
You will learn
- How the offline feature works, through demonstration
- How the synchronization code works
- How to handle errors that occur while syncing
-
Follow the instructions at Try Out the SAP BTP SDK Wizard for Android to create a new application using the SAP BTP SDK Wizard for Android and select Offline for the OData option on the Project Features tab. The push feature is not needed for this application.
-
Run the app. After the login process, a screen is displayed explaining that the offline store is opening. As the screen suggests, opening the offline store for the first time can take up to a few minutes. One technique to decrease this initial time is to only download data that is relevant to the user, such as customers that belong in their sales region.
-
When you get to the app’s home page, turn on airplane mode on your device, or disable Wi-Fi and data.
-
The entity list screen is populated based on the
metadata.xml
file retrieved when the application was created. Tap the Products list item.The Products screen makes a data request to display the available products. Notice that it succeeds without a working network connection. The data request is fulfilled from the offline store that was previously created and populated on the device. Tap the Accessories item to display the detail screen.
-
On the detail screen, tap the edit toolbar icon.
-
Make a change to the currency code and tap the save toolbar icon.
-
Navigate back to the app’s Home screen and tap Synchronize using the three-dot-menu in the top right of the title bar.
The sync should fail because you haven’t turned airplane mode off yet.
-
Turn off airplane mode or re-enable Wi-Fi/data and attempt a sync again. You will see a notification that describes the sync action.
When the sync completes, the change you made will have been applied to the back end.
Make sure you are selecting the right language above.
The offline store is populated based on objects called in using OfflineODataDefiningQuery
. The defining queries are located in OfflineWorkerUtil.java
, in the initializeOffline
method.
OfflineODataDefiningQuery customersQuery = new OfflineODataDefiningQuery("Customers", "Customers", false);
OfflineODataDefiningQuery productsQuery = new OfflineODataDefiningQuery("Products", "Products", true);
The offline store is populated based on objects called in using OfflineODataDefiningQuery
. The defining queries are located in OfflineWorkerUtil.kt
, in the initializeOffline
method.
val customersQuery = OfflineODataDefiningQuery("Customers", "Customers", false)
val productsQuery = OfflineODataDefiningQuery("Products", "Products", true)
Defining queries tell the OfflineODataProvider
(the class that manages the offline store) which entity sets to store on the device. In the case of the wizard-generated application, there is a defining query for each available entity by default, meaning that each entity is stored offline and available if the user doesn’t have an internet connection. For more information, see Defining Queries.
With an offline-enabled app, requests made against the entity sets that are included in the defining requests will always be fulfilled from the local offline store.
Make sure you are selecting the right language above.
The application allows users to make changes against a local offline store and synchronize manually at any time. The sync operation is performed by a worker. There are three operations that must be implemented in order to use the offline store functionality: open
, download
, and upload
. As their names suggest, the operations open the offline store, download server changes, and upload user changes, respectively. In the wizard-generated application, OfflineOpenWorker
implements open
during initialization and OfflineSyncWorker
implements a sync operation, which requires download
first, and then upload
.
-
In Android Studio, on Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeOfflineOpenWorker
to openOfflineOpenWorker.java
and examine theopen
method.The worker’s work is to call the
open
method of theOfflineODataProvider
class to perform the open operation and pass the given callbacks through.The
OfflineOpenWorker
class is called byopen
method inOfflineWorkerUtil.java
which is called byWizardFlowStateListener
when the user logs into the application. -
In Android Studio, on Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeOfflineSyncWorker
to openOfflineSyncWorker.java
and examine thedownload
andupload
methods.The worker’s work is to call the
download
andupload
method of theOfflineODataProvider
class to perform the sync operation and pass the given callbacks through.The
OfflineSyncWorker
class is called by thesync
method inOfflineWorkerUtil.java
, which is called byEntitySetListActivity
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 anupload
, the server will set the primary key for the client. Anupload
and adownload
are normally performed together because thedownload
may return updated values from the server, such as a newly-created primary key.
-
In Android Studio, on Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeOfflineOpenWorker
to openOfflineOpenWorker.kt
and examine theopen
method.The worker’s work is to call the
open
method of theOfflineODataProvider
class to perform the open operation and pass the given callbacks through.The
OfflineOpenWorker
class is called byopen
method inOfflineWorkerUtil.kt
which is called byWizardFlowStateListener
when the user logs into the application. -
In Android Studio, on Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeOfflineSyncWorker
to openOfflineSyncWorker.kt
and examine thedownload
andupload
methods.The worker’s work is to call the
download
andupload
method of theOfflineODataProvider
class to perform the sync operation and pass the given callbacks through.The
OfflineSyncWorker
class is called by thesync
method inOfflineWorkerUtil.kt
, which is called byEntitySetListActivity
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 anupload
, the server will set the primary key for the client. Anupload
and adownload
are normally performed together because thedownload
may return updated values from the server, such as a newly-created primary key.
For more information about how the offline store works, see the Offline API.
When syncing changes made while offline, conflicts can occur. One example might be if two people attempted to update a description field for the same product. Another might be updating a record that was deleted by another user. The ErrorArchive
provides a way to see details of any of the conflicts that may have occurred. The following instructions demonstrate how to use ErrorArchive
.
-
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.
-
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.
In this section we will create an Error Information screen that displays the details from the ErrorArchive
.
-
Press
Shift
twice and typestrings.xml
to openres\values\strings.xml
. -
Add the following values.
<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>
-
Create a new activity in the
app/java/com.sap.wizapp/mdui
folder by right-clicking, then selecting New > Activity > Empty Activity. Name the new activityErrorActivity
. -
Press
Shift
twice and typeactivity_error
to openres/layout/activity_error.xml
. -
Replace its contents with the following XML.
<?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" 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" android:theme="@style/AppTheme.AppBarOverlay"> <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/colorWhite" /> </com.google.android.material.appbar.AppBarLayout> <ScrollView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="wrap_content" android:layout_width="match_parent"> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 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" /> <View android:layout_width="match_parent" 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>
-
Replace the
ErrorActivity.java
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.package com.sap.wizapp.mdui; import androidx.appcompat.app.AppCompatActivity; import androidx.appcompat.widget.Toolbar; import android.os.Bundle; import android.view.MenuItem; import android.widget.TextView; import com.sap.wizapp.R; public class ErrorActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_error); Toolbar toolbar = findViewById(R.id.toolbar); setSupportActionBar(toolbar); getSupportActionBar().setDisplayHomeAsUpEnabled(true); int errorCode = getIntent().getIntExtra("ERROR_CODE", 0); String errorMethod = getIntent().getStringExtra("ERROR_METHOD"); String requestURL = getIntent().getStringExtra("ERROR_URL"); String errorMessage = getIntent().getStringExtra("ERROR_MESSAGE"); String body = getIntent().getStringExtra("ERROR_BODY"); ((TextView) (findViewById(R.id.requestStatusTextView))).setText("" + errorCode); if (errorMethod != null) { ((TextView) (findViewById(R.id.requestMethodTextView))).setText(errorMethod); } if (requestURL != null) { ((TextView) (findViewById(R.id.requestURLTextView))).setText(requestURL); } if (errorMessage != null) { ((TextView) (findViewById(R.id.requestMessageTextView))).setText(errorMessage); } if (body != null) { ((TextView) (findViewById(R.id.requestBodyTextView))).setText(body); } } @Override public boolean onOptionsItemSelected(MenuItem item) { finish(); return super.onOptionsItemSelected(item); } }
-
On Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeEntitySetListActivity
to openEntitySetListActivity.java
. -
In the
synchronize
method, find the line that performs theOfflineWorkerUtil.sync
method call. -
Right after the
progressBar.setVisibility(View.INVISIBLE);
line, in theSUCCEEDED
case of sync work state, add the following code, which queries the error archive and displays information to the user about the first error encountered:OfflineODataProvider provider = OfflineWorkerUtil.getOfflineODataProvider(); try { List<OfflineODataErrorArchiveEntity> errorArchive = provider.getErrorArchive(); for (OfflineODataErrorArchiveEntity errorEntity : errorArchive) { String requestURL = errorEntity.getRequestURL(); String method = errorEntity.getRequestMethod(); String message = errorEntity.getMessage(); Integer statusCode = errorEntity.getHttpStatusCode() != null ? errorEntity.getHttpStatusCode() : 0; String body = errorEntity.getRequestBody(); LOGGER.error("RequestURL: " + requestURL); LOGGER.error("HTTP Status Code: " + statusCode); LOGGER.error("Method: " + method); LOGGER.error("Message: " + message); LOGGER.error("Body: " + body); Intent errorIntent = new Intent(EntitySetListActivity.this, ErrorActivity.class); errorIntent.putExtra("ERROR_URL", requestURL); errorIntent.putExtra("ERROR_CODE", statusCode); errorIntent.putExtra("ERROR_METHOD", method); errorIntent.putExtra("ERROR_BODY", body); try { JSONObject jsonObj = new JSONObject(message); errorIntent.putExtra("ERROR_MESSAGE", jsonObj.getJSONObject("error").getString("message")); } catch (JSONException e) { 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/c2d571df73104f72b9f1b73e06c5609a/Latest/en-US/docs/user-guide/odata/Offline_OData_Handling_Failed_Requests.html#reverting-an-error-state // provider.deleteEntity(errorEntity, null, null); startActivity(errorIntent); break; //For simplicity, only show the first error encountered } } catch (OfflineODataException e) { e.printStackTrace(); }
After modification, the
SUCCEEDED
block should look like this:case SUCCEEDED: LOGGER.info("Offline sync done."); OfflineODataProvider provider = OfflineWorkerUtil.getOfflineODataProvider(); try { List<OfflineODataErrorArchiveEntity> errorArchive = provider.getErrorArchive(); for (OfflineODataErrorArchiveEntity errorEntity : errorArchive) { String requestURL = errorEntity.getRequestURL(); String method = errorEntity.getRequestMethod(); String message = errorEntity.getMessage(); Integer statusCode = errorEntity.getHttpStatusCode() != null ? errorEntity.getHttpStatusCode() : 0; String body = errorEntity.getRequestBody(); LOGGER.error("RequestURL: " + requestURL); LOGGER.error("HTTP Status Code: " + statusCode); LOGGER.error("Method: " + method); LOGGER.error("Message: " + message); LOGGER.error("Body: " + body); Intent errorIntent = new Intent(EntitySetListActivity.this, ErrorActivity.class); errorIntent.putExtra("ERROR_URL", requestURL); errorIntent.putExtra("ERROR_CODE", statusCode); errorIntent.putExtra("ERROR_METHOD", method); errorIntent.putExtra("ERROR_BODY", body); try { JSONObject jsonObj = new JSONObject(message); errorIntent.putExtra("ERROR_MESSAGE", jsonObj.getJSONObject("error").getString("message")); } catch (JSONException e) { 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/c2d571df73104f72b9f1b73e06c5609a/Latest/en-US/docs/user-guide/odata/Offline_OData_Handling_Failed_Requests.html#reverting-an-error-state // provider.deleteEntity(errorEntity, null, null); startActivity(errorIntent); break; //For simplicity, only show the first error encountered } } catch (OfflineODataException e) { e.printStackTrace(); } break;
-
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, 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 theErrorArchive
entry, reverting the entity to its previous state. For more information on error handling, see Handling Errors and Conflicts and Handling Failed Requests.
-
Press
Shift
twice and typestrings.xml
to openres\values\strings.xml
. -
Add the following values.
<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>
-
Create a new activity in the
app/java/com.sap.wizapp/mdui
folder by right-clicking, then selecting New > Activity > Empty Activity. Name the new activityErrorActivity
. -
Press
Shift
twice and typeactivity_error
to openres/layout/activity_error.xml
. -
Replace its contents with the following XML.
<?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" 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" android:theme="@style/AppTheme.AppBarOverlay"> <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/colorWhite" /> </com.google.android.material.appbar.AppBarLayout> <ScrollView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="wrap_content" android:layout_width="match_parent"> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 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" /> <View android:layout_width="match_parent" 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>
-
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.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) } }
-
On Windows, press
Ctrl+N
, or, on a Mac, presscommand+O
, and typeEntitySetListActivity
to openEntitySetListActivity.kt
. -
In the
synchronize
method, find the line that performs theOfflineWorkerUtil.sync
method call. -
Right after the
sync_determinate.visibility = View.INVISIBLE
line, in theWorkInfo.State.SUCCEEDED
block, add the following code, which queries the error archive and displays information to the user about the first error encountered: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 = JSONObject(message) 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/c2d571df73104f72b9f1b73e06c5609a/Latest/en-US/docs/user-guide/odata/Offline_OData_Handling_Failed_Requests.html#reverting-an-error-state // provider.deleteEntity(errorEntity, null, null); startActivity(errorIntent) break //For simplicity, only show the first error encountered } } catch (e: OfflineODataException) { e.printStackTrace() }
After modification, the
WorkInfo.State.SUCCEEDED
block should look like this: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 = JSONObject(message) 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/c2d571df73104f72b9f1b73e06c5609a/Latest/en-US/docs/user-guide/odata/Offline_OData_Handling_Failed_Requests.html#reverting-an-error-state // provider.deleteEntity(errorEntity, null, null); startActivity(errorIntent) break //For simplicity, only show the first error encountered } } catch (e: OfflineODataException) { e.printStackTrace() } }
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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 theErrorArchive
entry, reverting the entity to its previous state. For more information on error handling, see Handling Errors and Conflicts and Handling Failed Requests.
Further information on using the offline feature can be found at Step by Step with the SAP BTP SDK for Android — Part 6 — Offline OData.
Congratulations! You have created an offline-enabled app using the SAP BTP SDK Wizard for Android and examined how the ErrorArchive
can be used to view synchronization errors!