使用SAP OData offline庫實作Android應用的離線(offline)模式

打開Android studio，在工程的build.gradle裡加入下面的依賴，導入SAP OData offline庫：

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

點選Sync now：

建立一個java檔案：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注釋掉，改為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;
}           

建立LogonActivity.java，調用之前實作的sapServiceManager.openODataStore:

第一次運作應用，會發現offline OData store的初始化日志：

現在可以測試離線模式了，打開移動裝置的飛行模式：

選擇存儲于OData offline store上的某個客戶，點選編輯按鈕：

修改city字段：

關閉該應用，關閉裝置的飛行模式，再啟動該應用，在logcat裡能觀察到之前處于離線模式修改的資料已經自動同步到了背景online store裡：

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