解决方案。
我自己找到了解决方案。我不需要访客模式。我刚刚实现了以下逻辑。
JsonPasrer。
此类仅从 JSON 文件中读取数据。
public class JsoinParser {
/**
* Reads a JSON file to a string
*
* @param fileName JSON file name
* @return null if reading failed
*/
private String readToString(String fileName) throws IOException {
StringBuilder resultBuilder = new StringBuilder();
String filePath = mContext.getExternalFilesDir(null).getAbsolutePath() + File.separatorChar + fileName;
BufferedReader bufferedReader = null;
try {
bufferedReader = new BufferedReader(new FileReader(filePath));
String line;
while ((line = bufferedReader.readLine()) != null) {
resultBuilder.append(line);
}
} finally {
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
Log.e("%s", "Failed to close the BufferedReader instance");
}
}
}
return resultBuilder.toString();
}
public List<Organization> readOrgs() throws JSONException, IOException {
JSONArray array = new JSONArray(readToString(FilesNames.ORGS));
List<Organization> list = new ArrayList<JsonParser.Organization>();
// TODO: read here and fill
return list;
}
public List<Continent> readContinents() throws JSONException, IOException {
JSONArray array = new JSONArray(readToString(FilesNames.CONTINENTS));
List<Continent> list = new ArrayList<JsonParser.Continent>();
for (int i = 0; i < array.length(); i++) {
JSONObject object = array.getJSONObject(i);
list.add(new Continent(object.getLong(ID), object.getString(NAME)));
}
return list;
}
public List<Country> readCountries() throws JSONException, IOException {
JSONArray array = new JSONArray(readToString(FilesNames.COUNTRIES));
List<Country> list = new ArrayList<JsonParser.Country>();
for (int i = 0; i < array.length(); i++) {
JSONObject object = array.getJSONObject(i);
long id = object.getLong(ID);
String name = object.getString(NAME);
List<Long> orgsIds = new ArrayList<Long>();
try {
JSONArray orgs = object.getJSONArray(ORGS_IDS);
orgsIds = new ArrayList<Long>();
for (int j = 0; j < orgs.length(); j++) {
orgsIds.add(orgs.getLong(j));
}
} catch (JSONException e) {
Log.v("%s", name + " is not a member of any international organizations");
}
long continentId = object.getLong(CONTINENT_ID);
list.add(new Country(id, name, orgsIds, continentId));
}
return list;
}
/**
* Common base class for all the entities read from JSON file. The entities are {@link Country},
* {@link Organization}, and {@link Continent}
*
* @author Red Planet
*
*/
abstract class BaseEntity {
String name;
long id;
List<ContentProviderOperation> operations = new ArrayList<ContentProviderOperation>();
private BaseEntity(long id, String name) {
this.id = id;
this.name = name;
}
public long getId() {
return id;
}
// Insert all the data within a transaction
abstract public List<ContentProviderOperation> getOperations();
public String getName() {
return name;
}
}
public class Country extends BaseEntity {
private List<Long> orgsIds;
private long continentId;
public Country(long id, String name, List<Long> orgsIds, long continentId) {
super(id, name);
this.orgsIds = new ArrayList<Long>();
this.orgsIds.addAll(orgsIds);
this.continentId = continentId;
}
@Override
public List<ContentProviderOperation> getOperations() {
ContentValues values = new ContentValues();
// TODO: fill ContentValues with the data which will be inserted
return operations;
}
}
public class Organization extends BaseEntity {
private Organization(long id, String name) {
super(id, name);
}
@Override
public List<ContentProviderOperation> getOperations() {
ContentValues values = new ContentValues();
// TODO: fill ContentValues with the data which will be inserted
return operations;
}
}
public class Continent extends BaseEntity {
private Continent(long id, String name) {
super(id, name);
}
@Override
public List<ContentProviderOperation> getOperations() {
ContentValues values = new ContentValues();
// TODO: fill ContentValues with the data which will be inserted
return operations;
}
}
}
JsonParserHelper。
此类获取由readX方法填充的数组并填充我的数据库。
public class JsonParserHelper {
public void insert(Context context, List<? extends BaseEntity> entities)
throws OperationApplicationException, RemoteException {
ArrayList<ContentProviderOperation> operations = new ArrayList<ContentProviderOperation>();
for (BaseEntity entity : entities) {
operations.addAll(entity.getOperations());
}
context.getContentResolver().applyBatch(DatabaseProvider.AUTHORITY, operations);
}
}