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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