使用SAP OData offline库实现Android应用的离线(offline)模式

打开Android studio，在工程的build.gradle里加入下面的依赖，导入SAP OData offline库：

implementation group:'com.sap.cloud.android', name:'offline-odata', version: sdkVersion

点击Sync now：

新建一个java文件：SAPServiceManager.java

使用的import如下：

import android.content.Context; import android.util.Log; import android.widget.Toast; import com.sap.cloud.mobile.odata.core.AndroidSystem; import com.sap.cloud.mobile.odata.offline.OfflineODataDefiningQuery; import com.sap.cloud.mobile.odata.offline.OfflineODataException; import com.sap.cloud.mobile.odata.offline.OfflineODataParameters; import com.sap.cloud.mobile.odata.offline.OfflineODataProvider; import java.net.MalformedURLException; import java.net.URL; // 将OfflineODataProvider注释掉，改为OfflineODataProvider //private OnlineODataProvider provider; private OfflineODataProvider provider; private static final String TAG = SAPServiceManager.class.getName(); OData offiline datastore的setup方法： public void openODataStore(Action0 callback, Context context) { setupOfflineOData(callback, context); } private void setupOfflineOData(Action0 callback, Context context) { try { if (configurationData.loadData()) { Toast.makeText(context, "Opening the offline store which may take a few moments the first time it is opened.", Toast.LENGTH_LONG).show(); //Initialize application context for use by OfflineODataProvider AndroidSystem.setContext(context); //commonly set parameters include setStoreEncryptionKey, setStoreName, setStorePath OfflineODataParameters offParam = new OfflineODataParameters(); String serviceUrl = configurationData.getServiceUrl(); URL url = new URL(serviceUrl + CONNECTION_ID_ESPMCONTAINER); provider = new OfflineODataProvider(url, offParam, ClientProvider.get()); //Specifies which entities we wish to include in the offline store provider.addDefiningQuery(new OfflineODataDefiningQuery("Customers", "Customers", false)); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (OfflineODataException e) { e.printStackTrace(); } //opens the offline store. This can take a minute or so the first time it is called as it is created and populated. Log.d(TAG, "About to call open on the offline store."); provider.open(() -> { Log.d(TAG, "Offline store opened."); eSPMContainer = new ESPMContainer(provider); callback.call(); syncOfflineData(); //TODO could be triggered via a menu action }, (OfflineODataException offlineODataException) -> { Log.d(TAG, "Offline store did not open.", offlineODataException); }); } public void syncOfflineData() { //send the local changes to the back end OData service Log.d(TAG, "About to call provider.upload."); provider.upload(() -> { Log.d(TAG, "Successfully uploaded the changed data."); //get changes from the back end OData service. provider.download(() -> { Log.d(TAG, "Successfully downloaded the changed data."); }, (error) -> { Log.d(TAG, "Failed when downloading the changed data with error: " + error.getMessage()); }); }, (error) -> { Log.d(TAG, "Failed when uploading the changed data with error: " + error.getMessage()); }); } public String getServiceRoot() { if (configurationData.loadData()) { String serviceUrl = configurationData.getServiceUrl(); if (serviceRoot == null) { serviceRoot = serviceUrl + "/" + CONNECTION_ID_ESPMCONTAINER; } } else { throw new IllegalStateException("SAPService manager configurationData.loadData() failed."); } return serviceRoot; }

新建LogonActivity.java，调用之前实现的sapServiceManager.openODataStore:

第一次运行应用，会发现offline OData store的初始化日志：

现在可以测试离线模式了，打开移动设备的飞行模式：

选择存储于OData offline store上的某个客户，点击编辑按钮：

修改city字段：

关闭该应用，关闭设备的飞行模式，再启动该应用，在logcat里能观察到之前处于离线模式修改的数据已经自动同步到了后台online store里：

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