我正在开发我的应用程序，其中存储引号。 有关我从服务器下载的报价的数据。 我想要用户下载10个引号（当时数据添加到本地数据库），如果他滚动这10个引号，将下载新数据（再次10）。 例如，在facebook磁带中（将数据添加到本地db）。 但我还需要将本地数据库与服务器数据库同步。 我不明白如何将这一切结合起来。
下载数据 - 在这里，我从服务器db的id传递要从中下载的id。
class DownloadAndParseJson extends AsyncTask<Integer, Void, ArrayList<QuoteObject>> {
interface AsyncResponse {
void processFinish(ArrayList<QuoteObject> output);
}
private AsyncResponse delegate = null;
DownloadAndParseJson(AsyncResponse delegate){
this.delegate = delegate;
}
private static final String TAG = "###" + "DownloadAndParseJson";
@Override
protected ArrayList<QuoteObject> doInBackground(Integer... params) {
Log.i(TAG, "Starting download quotes from " + params[0] + " id");
if (params.length == 0) {
return null;
}
int id = params[0];
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
String countriesJsonStr = null;
try {
final String BASIC_URL = "http://*******.com";
final String ID_PARAM = "id";
Uri builtUri = Uri.parse(BASIC_URL).buildUpon()
.appendQueryParameter(ID_PARAM, Integer.toString(id))
.build();
URL url = new URL(builtUri.toString());
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
return null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
buffer.append(line + "\n");
}
if (buffer.length() == 0) {
return null;
}
countriesJsonStr = buffer.toString();
Log.v(TAG, "download end");
} catch (IOException e) {
Log.e(TAG, "Error", e);
return null;
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e(TAG, "Error", e);
}
}
}
Log.i(TAG, "End download quotes");
return getArrayParsedJson(countriesJsonStr);
}
@Override
protected void onPostExecute(ArrayList<QuoteObject> result) {
Log.i(TAG, "Downloaded " + result.size() + " quotes");
delegate.processFinish(result);
}
private ArrayList<QuoteObject> getArrayParsedJson(String jsonStr){
Gson gson = new Gson();
Type collectionType = new TypeToken<ArrayList<QuoteObject>>(){}.getType();
return gson.fromJson(jsonStr, collectionType);
}
}
使用数据库 - 这里我存储引用对象
public class RealmHelper {
private static final String TAG = "###" + "RealmHelper";
Context context;
public RealmHelper(Context context) {
this.context = context;
}
public void write(ArrayList<QuoteObject> quoteObjectArrayList) {
Realm.init(context);
Realm realm = Realm.getDefaultInstance();
realm.beginTransaction();
for (QuoteObject quoteObject : quoteObjectArrayList){
realm.copyToRealm(quoteObject);
}
realm.commitTransaction();
}
public ArrayList<QuoteObject> read() {
Realm.init(context);
Realm realm = Realm.getDefaultInstance();
return new ArrayList<>(realm.where(QuoteObject.class).findAll());
}
public void delete() {
Realm.init(context);
Realm realm = Realm.getDefaultInstance();
final RealmResults<QuoteObject> countries = realm.where(QuoteObject.class).findAll();
realm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
countries.deleteAllFromRealm();
Log.i(TAG, "size = " + countries.size());
}
});
}
}
MainActivity
public class MainActivity extends AppCompatActivity
implements DownloadAndParseJson.AsyncResponse{
.
.
RVAdapter adapter;
private ArrayList<QuoteObject> quoteObjectArrayList;
.
.
protected void onCreate(){
.
.
.
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
adapter = new RVAdapter(this, quoteObjectArrayList);
recyclerView.setAdapter(adapter);
}
@Override
public void processFinish(ArrayList<QuoteObject> output) {
if (output.size() != 0) {
quoteObjectArrayList = output;
Log.i(TAG, "processFinish() returned outputArray size " + output.size());
} else
Toast.makeText(this, "Not found quotes", Toast.LENGTH_SHORT).show();
}
RecyclerView.Adapter - 使用卡片视图显示引号。
class RVAdapter extends RecyclerView.Adapter<RVAdapter.PersonViewHolder>
implements DownloadAndParseJson.AsyncResponse{
private static final String TAG = "###" + "RVAdapter";
private Context context;
private boolean hasMoreItems;
private ArrayList<QuoteObject> quoteObjectArrayList;
RVAdapter(Context context, ArrayList<QuoteObject> quoteObjectArrayList){
this.context = context;
this.hasMoreItems = true;
this.quoteObjectArrayList = quoteObjectArrayList;
Log.i(TAG, "quoteObjectArrayList = " + quoteObjectArrayList.size());
}
private void notifyNoMoreItems(){
hasMoreItems = false;
Toast.makeText(context, "No More Items", Toast.LENGTH_SHORT).show();
}
@Override
public RVAdapter.PersonViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
View view = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.card_of_quote, viewGroup, false);
return new PersonViewHolder(view);
}
@Override
public void onBindViewHolder(final RVAdapter.PersonViewHolder holder, int position) {
Log.i(TAG, "Card position = " + position);
if (position == quoteObjectArrayList.size() && hasMoreItems){
new DownloadAndParseJson(this).execute(Integer.parseInt(quoteObjectArrayList.get(position).getId()));
}
holder.contentOfQuote.setText(quoteObjectArrayList.get(position).getQuote());
holder.authorQuote.setText(quoteObjectArrayList.get(position).getAuthor());
holder.ratingBar.setOnRatingChangeListener(new MaterialRatingBar.OnRatingChangeListener() {
@Override
public void onRatingChanged(MaterialRatingBar ratingBar, float rating) {
//ratingBar.setRight(Integer.parseInt(quoteObjectArrayList.get(position).getId()));
}
});
holder.btnShareQuote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, holder.contentOfQuote.getText()
+ "\n" + holder.authorQuote.getText() );
sendIntent.setType("text/plain");
context.startActivity(sendIntent);
}
});
holder.btnViewComment.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//View Comments
}
});
}
@Override
public int getItemCount() {
return quoteObjectArrayList.size();
}
@Override
public void processFinish(ArrayList<QuoteObject> output) {
if (output.size() != 0) {
quoteObjectArrayList.addAll(output);
Log.i(TAG, "Total quoteArray Size = " + quoteObjectArrayList.size());
new RealmHelper(context).write(output); // NEED separate throw
} else notifyNoMoreItems();
}
static class PersonViewHolder extends RecyclerView.ViewHolder {
CardView cardView;
TextView contentOfQuote, authorQuote;
MaterialRatingBar ratingBar;
ImageButton btnViewComment, btnShareQuote;
TextView rating;
public PersonViewHolder(View itemView) {
super(itemView);
this.cardView = (CardView) itemView.findViewById(R.id.cardView);
this.contentOfQuote = (TextView) itemView.findViewById(R.id.contentOfQuote);
this.authorQuote = (TextView) itemView.findViewById(R.id.authorQuote);
this.btnViewComment = (ImageButton) itemView.findViewById(R.id.btnViewComment);
this.btnShareQuote = (ImageButton) itemView.findViewById(R.id.btnShareQuote);
this.ratingBar = (MaterialRatingBar) itemView.findViewById(R.id.ratingBar);
this.rating = (TextView) itemView.findViewById(R.id.txtRating);
}
}
}
现在我需要将所有这些结合起来。
结果应该是：
请帮帮我。
感谢。
答案 0 :(得分：1)
如果您将RealmResults与RealmChangeListener和Realm的通知系统一起使用，那么这将更加容易。请参阅official documentation。
Button btn = new Button(this);
btn.SetBackgroundResource(Resource.Drawable.RoundedButton);
和
class DownloadAndParseJson extends AsyncTask<Integer, Void, Void> {
DownloadAndParseJson(){
}
private static final String TAG = "###" + "DownloadAndParseJson";
@Override
protected Void doInBackground(Integer... params) {
Log.i(TAG, "Starting download quotes from " + params[0] + " id");
if (params.length == 0) {
return null;
}
int id = params[0];
try {
final List<QuoteObject> quotes = retrofitService.getQuotes(id).execute().body();
if(quotes == null) {
throw new RuntimeException("Download failed");
}
try(Realm realm = Realm.getDefaultInstance()) {
realm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.insert(quotes);
}
});
}
} catch (Exception e) {
Log.e(TAG, "Error", e);
return null;
}
Log.i(TAG, "End download quotes");
return null;
}
@Override
protected void onPostExecute(Void ignored) {
}
}
和
class RVAdapter extends RealmRecyclerViewAdapter<QuoteObject, RVAdapter.PersonViewHolder> {
private static final String TAG = "###" + "RVAdapter";
RVAdapter(OrderedRealmCollection<QuoteObject> quotes) {
super(quotes, true);
}
// onCreateViewHolder
// onBindViewHolder
// view holder
}
和一些“确实下载了所有”的逻辑，虽然这需要更聪明的错误处理;并且“正在下载数据”，这样当您向下滚动时就不会发出垃圾邮件请求。