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我在TabLayout中使用帶有CardView的RecyclerView。如果我在滑動到另一個選項卡並返回第一個選項卡後上下滾動，RecyclerView將複製第一個選項卡上的卡片。我如何去防止重複？我將在帖子的評論中發佈pastebin鏈接到代碼的其餘部分。Android：使用RecyclerView和CardView重複項目 - 如何停止重複？
MyRecyclerViewAdapater.java：
package com.benrcarvergmail.cvhsmobileapplication;
import android.support.v7.widget.CardView;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
public class MyRecyclerViewAdapater extends RecyclerView.Adapter<MyRecyclerViewAdapater.MyViewHolder> {
private List<AnnouncementsFragment.Announcement> mDataset; // ArrayList implementation to hold data
private static final String TAG = "MyRecyclerViewAdapter";
// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public static class MyViewHolder extends RecyclerView.ViewHolder {
public CardView mCardView; // The CardView itself
public TextView mInfoTextView; // The announcement's text
public TextView mIntroTextView; // The announcement's intro text
public TextView mDateTextView; // The announcement's date
public TextView mTitleTextView; // The announcement's title
public ImageView mCardViewIcon; // The announcement's icon
private boolean isExpanded = false;
// References to all of the elements of the CardView
public MyViewHolder(View v) {
super(v); // Call the super() constructor
mCardView = (CardView) v.findViewById(R.id.card_view); // The CardView
mIntroTextView = (TextView) v.findViewById(R.id.intro_text_view); // The intro text
mInfoTextView = (TextView) v.findViewById(R.id.info_text_view); // The text
mTitleTextView = (TextView) v.findViewById(R.id.title_text_view); // The title
mDateTextView = (TextView) v.findViewById(R.id.date_text_view); // The date
mCardViewIcon = (ImageView) v.findViewById(R.id.card_view_icon); // The icon
v.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.i(TAG, "onClick() called!");
// If it is already expanded, collapse it. Otherwise, expand it.
if (isExpanded) {
// Collapses the CardView and sets isExpanded to false
Log.i(TAG, "isExpanded: " + isExpanded);
isExpanded = collapse(v); // returns false
} else {
// Expands the CardView and sets isExpanded to true
Log.i(TAG, "isExpanded: " + isExpanded);
isExpanded = expand(v); // returns True
}
}
});
}
// Expand the CardView
private boolean expand(View cardView) {
// Make the intro text invisible and make the full text visible
mIntroTextView.setVisibility(View.GONE);
mInfoTextView.setVisibility(View.VISIBLE);
return true;
}
// Collapse the CardView
private boolean collapse(View cardView) {
// Make the intro text visible and make the full text invisible
mInfoTextView.setVisibility(View.GONE);
mIntroTextView.setVisibility(View.VISIBLE);
return false;
}
}
// Provide a suitable constructor (depends on the kind of dataset)
public MyRecyclerViewAdapater(List<AnnouncementsFragment.Announcement> myDataset) {
mDataset = myDataset;
setHasStableIds(true);
}
// Sets a new Dataset to be our Dataset of Announcements
public void updateList(List<AnnouncementsFragment.Announcement> newData) {
mDataset = newData;
notifyDataSetChanged();
}
// Add an Announcement to our Dataset
public void addItem(int position, AnnouncementsFragment.Announcement newAnnouncement) {
mDataset.add(position, newAnnouncement);
notifyItemInserted(position);
}
// Remove an Announcement from our Dataset
public void removeItem(int position) {
mDataset.remove(position);
notifyItemRemoved(position);
}
// Create new views (invoked by the layout manager)
@Override
public MyRecyclerViewAdapater.MyViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
// create a new view
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.card_item, parent, false);
// set the view's size, margins, paddings and layout parameters
MyViewHolder vh = new MyViewHolder(v);
return vh;
}
@Override
/*
This method internally calls onBindViewHolder(ViewHolder, int) to update
the RecyclerView.ViewHolder contents with the item at the given position
and also sets up some private fields to be used by RecyclerView.
*/
public void onBindViewHolder(MyViewHolder holder, int position) {
/* Get the proper Announcement's intro text (generate it, it isn't already generated
upon or during instantiation) and assign it to the appropriate TextView. */
holder.mIntroTextView.setText(mDataset.get(position).generateIntro());
/* Get the proper Announcement's text and assign the
informational TextView's text to a shortened version of the
text. The full text will be displayed upon expansion of the CardView. */
holder.mInfoTextView.setText(mDataset.get(position).getText());
/* Get the proper Announcement's date and assign the
date TextView's text to the aforementioned date.toString() */
holder.mDateTextView.setText(mDataset.get(position).getAnnouncementDate().toString());
/* Get the proper Announcement's title and assign the
title TextView's text to the aforementioned title. */
holder.mTitleTextView.setText(mDataset.get(position).getTitle());
// Ensure that only the intro text is visible at first
holder.mInfoTextView.setVisibility(View.GONE);
holder.mIntroTextView.setVisibility(View.VISIBLE);
int imagePath = mDataset.get(position).getImageSource();
if(!(imagePath == Integer.MIN_VALUE)) {
/* When Image support is fully implemented, we'd assign the Image a source.
For now, however, nothing happens except we print that an Image was specified. */
Log.i(TAG, "An image ID was specified for the Announcement "
+ mDataset.get(position).getTitle()); // We could use .toString() instead of .getTitle()
}
Log.i(TAG, "onBindViewHolder() called");
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
// Returns number of elements in the mDataset List
public int getItemCount() {
if (mDataset == null) {
return -1;
} else {
return mDataset.size();
}
}
}
AnnouncementsFragment.java：
package com.benrcarvergmail.cvhsmobileapplication;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;;
import java.util.ArrayList;
import java.util.Date;
/**
* The type Announcements fragment.
*/
public class AnnouncementsFragment extends Fragment {
private ArrayList<Announcement> data;
private static final String TAG = "AnnouncementsFragment";
/**
* Instantiates a new Announcements fragment.
*/
public AnnouncementsFragment() {
// Instantiate the data ArrayList so we may populate it during onCreateView()
data = new ArrayList<Announcement>();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_announcements, container, false);
// Create object reference to the RecyclerView created in fragment_announcements.xml
RecyclerView rv = (RecyclerView) rootView.findViewById(R.id.rv_recycler_view);
// Ensure that its size is fixed (unchanging)
rv.setHasFixedSize(true);
// Populate the data ArrayList. We currently do not utilize the boolean return type
populateData();
// Create an adapter for the RecyclerView, passing the ArrayList of text we want displayed
MyRecyclerViewAdapater adapter = new MyRecyclerViewAdapater(data);
// Set the RecyclerView's adapater to the one we just created
rv.setAdapter(adapter);
// A LinearLayoutManager is a A RecyclerView.LayoutManager
// implementation which provides similar functionality to ListView.
LinearLayoutManager llm = new LinearLayoutManager(getActivity());
rv.setLayoutManager(llm);
return rootView;
}
// This will populate the data ArrayList with the data we want to display. This may
// eventually get more complicated (if we require lots of different data other than
// text to be shown. Additionally, this will eventually grab the information from a server.
private boolean populateData() {
// This text was generated with an Android Studio plugin known as Insert Dummy Text. That
// fact is completely useless but nevertheless, it's a good plugin and I recommend it. I
// add a new line (+ "\n" to each String to ensure it doesn't get cut off. This may mess
// things up of the String is only one line though, so we'll see what happens.
// Add each new announcement to the ArrayList. We are creating the Announcements when we pass them.
data.add(new Announcement("Test Announcement #1",
"Chilled celery can be made melted by seasoning with white wine. " +
"Turkey mousse has to have a delicious, sour pickles component." + "\n",
Integer.MIN_VALUE,
new Date()));
data.add(new Announcement("Test Announcement #2",
"Cook iced lettuces in a bottle with soy sauce for about an hour to increase their viscosity." +
"Remember: scraped melon tastes best when peeled in a frying pan varnished with dill." + "\n",
Integer.MIN_VALUE,
new Date()));
data.add(new Announcement("Test Announcement #3",
"After warming the chickpeas, enamel avocado, rhubarb and maple syrup " +
"with it in a plastic bag. Toast two chocolates, rice, and marmalade in a large " +
"frying pan over medium heat, cook for a dozen minutes and soak with some " +
"zucchini."+ "\n",
Integer.MIN_VALUE,
new Date()));
data.add(new Announcement("Test Announcement #4",
"All children like pressed raspberries in peanut sauce and woodruff." +
"Try draining paste rinseed with gold tequila, enameled with corn syrup."+ "\n",
Integer.MIN_VALUE,
new Date()));
data.add(new Announcement("Test Announcement #5",
"Mash peanut butter quickly, then mix with whiskey and serve thoroughly in pan." +
"Mash margarine smoothly, then mix with kefir and serve fairly in bottle." + "\n",
Integer.MIN_VALUE,
new Date()));
return true; // May eventually return false if unable to pull data from server
}
/**
* Announcement class to store all data pertaining to what might be
* displayed or associated with any given announcement. This implementation
* is subject to change at any point, as a better methodology may be discovered.
*
* There are a lot of possible future features to announcements. The possibilities
* include: customisable icon, Announcement type (club, sports, general, weather, etc.),
* Announcement caster (dedicated field pertaining to whom the announcement is from), etc.
*/
class Announcement {
private String title; // The announcement's title
private String text; // The announcement's textual information
private int imageSource; // In the format R.id.XYZ
private Date announcementDate; // The date the announcement was posted.
/**
* Instantiates a new Announcement with a title, text, an image, and a date.
*
* @param title the announcement's title
* @param text the text-based information for the Announcement
* @param source the source for the (optional) image in the format R.id.XYZ
* @param date the date of the announcement
*/
public Announcement(String title, String text, int source, Date date) {
this.title = title;
this.text = text;
imageSource = source;
announcementDate = date;
}
/**
* Instantiates a new Announcement with a title, text, and a date.
* This also will assign imageSource to Integer.MIN_VALUE so it will
* be something that we can check for and that won't be used automatically by accident.
*
* @param title the announcement's title
* @param text the text-based information for the Announcement
* @param date the date of the announcement
*/
public Announcement(String title, String text, Date date) {
this.title = title;
this.text = text;
imageSource = Integer.MIN_VALUE;
announcementDate = date;
}
/**
* Instantiates a new Announcement with text, an image, and a date.
*
* @param text the text-based information for the Announcement
* @param source the source for the (optional) image in the format R.id.XYZ
* @param date the date of the announcement
*/
public Announcement(String text, int source, Date date) {
this.text = text;
imageSource = source;
announcementDate = date;
}
/**
* Instantiates a new Announcement with just the text and a date.
* This also will assign imageSource to Integer.MIN_VALUE so it will
* be something that we can check for and that won't be used automatically by accident.
* @param text the text-based information for the Announcement
* @param date the date of the announcement
*/
public Announcement(String text, Date date) {
this.text = text;
announcementDate = date;
imageSource = Integer.MIN_VALUE;
}
/**
* Instantiates a new Announcement with just an image and a date.
*
* @param source the source for the (optional) image in the format R.id.XYZ
* @param date the date of the announcement
*/
public Announcement(int source, Date date) {
imageSource = source;
announcementDate = date;
}
/**
* Instantiates a new Announcement with just an image. The date is
* automatically assigned to the date and time of the method call.
*
* @param source the source for the (optional) image in the format R.id.XYZ
*/
public Announcement(int source) {
imageSource = source;
announcementDate = new Date();
}
/**
* Instantiates a new Announcement with just text. The date is
* automatically assigned to the date and time of the method call.
* This also will assign imageSource to Integer.MIN_VALUE so it will
* be something that we can check for and that won't be used automatically by accident.
* @param text the text for the Announcement.
*/
public Announcement(String text) {
this.text = text;
imageSource = Integer.MIN_VALUE;
announcementDate = new Date();
}
/**
* Gets announcement date.
*
* @return the announcement date
*/
public Date getAnnouncementDate() {
return announcementDate;
}
/**
* Sets announcement date.
*
* @param announcementDate the new announcement date
*/
public void setAnnouncementDate(Date announcementDate) {
this.announcementDate = announcementDate;
}
/**
* Gets image source.
*
* @return the Announcement's image source
*/
public int getImageSource() {
return imageSource;
}
/**
* Sets image source.
*
* @param imageSource the new image source in the form R.id.XYZ
*/
public void setImageSource(int imageSource) {
this.imageSource = imageSource;
}
/**
* Gets text.
*
* @return the Announcement's text
*/
public String getText() {
return text;
}
/**
* Sets text.
*
* @param text the new text value
*/
public void setText(String text) {
this.text = text;
}
/**
* Gets title.
*
* @return the Announcement's title
*/
public String getTitle() {
return title;
}
/**
* Sets title.
*
* @param title the new Announcement title
*/
public void setTitle(String title) {
this.title = title;
}
@Override
public boolean equals(Object obj) {
// If obj is null, return false
if (obj == null) {
return false;
}
// clazz.isAssignableFrom(Foo.class) returns true if the
// clazz object is a superclass or superinterface of Foo
if (!Announcement.class.isAssignableFrom(obj.getClass())) {
return false;
}
// Check to see if all necessary variables are equal or not
final Announcement objPerson = (Announcement) obj;
if ((this.announcementDate == null) ? (objPerson.announcementDate != null) : !this.announcementDate.equals(objPerson.announcementDate)) {
return false;
}
if (this.imageSource != objPerson.imageSource) {
return false;
}
if ((this.text == null) ? (objPerson.text != null) : !this.text.equals(objPerson.text)) {
return false;
}
if ((this.title == null) ? (objPerson.title != null) : !this.title.equals(objPerson.title)) {
return false;
}
return true;
}
/**
* Converts Announcement to String form in the format
* Announcement: ANNOUNCEMENT_TITLE, ANNOUNCEMENT_TEXT, ANNOUNCEMENT_DATE, ANNOUNCEMENT_IMAGE_SOURCE
*/
@Override
public String toString() {
return "Announcement: " + title + ", " + text + ", " + announcementDate.toString() + ", " + imageSource;
}
/**
* This method creates a substring from the announcement's text to be used as a intro of
* sorts. Basically, this generated String can be used to display on each CardView when
* the CardView isn't expanded. Upon expansion, the CardView will display the full text
* of the announcement.
*
* @return a substring of the announcement
*/
public String generateIntro() {
Log.i(TAG, "generateIntro() called!");
if (text.length() == 0) {
return "...";
} else {
// Ensure that the text is long to generate an 80-character substring
if (text.length() >= 80) {
String toReturn = text.substring(0, 80) + "...";
// Log.i(TAG, "Returning: " + toReturn + "\n for String: " + text);
return toReturn;
} else {
// Log.i(TAG, "Returning full String for String: \n" + text);
return text; // The text is already short enough.
}
}
}
}
}
MainActi vity.java http://pastebin.com/YsiL7yfn card_item.xml http://pastebin.com/wxFni7vq – Scusemua