https://github.com/codepath/fb-recyclerview-demo
Proposed RecyclerView Demo changes
https://github.com/codepath/fb-recyclerview-demo
Last synced: 8 months ago
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Proposed RecyclerView Demo changes
- Host: GitHub
- URL: https://github.com/codepath/fb-recyclerview-demo
- Owner: codepath
- Created: 2015-08-07T19:14:15.000Z (over 10 years ago)
- Default Branch: master
- Last Pushed: 2018-05-25T19:52:38.000Z (over 7 years ago)
- Last Synced: 2023-05-10T14:13:28.404Z (over 2 years ago)
- Language: Java
- Size: 858 KB
- Stars: 8
- Watchers: 14
- Forks: 9
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# RecyclerView Demo
This is a simple contacts app to demonstrate how to display a list of objects using a `RecyclerView`.
## Contact Model
Ask students to copy the following `Contact` model:
```
public class Contact {
private String mName;
private boolean mOnline;
public Contact(String name, boolean online) {
mName = name;
mOnline = online;
}
public String getName() {
return mName;
}
public boolean isOnline() {
return mOnline;
}
private static int lastContactId = 0;
public static List createContactsList(int numContacts) {
List contacts = new ArrayList<>();
for (int i = 1; i <= numContacts; i++) {
contacts.add(new Contact("Person " + ++lastContactId, i <= numContacts / 2));
}
return contacts;
}
}
```
## Key Demonstration Points
### Recycled items
Without re-enabling the button on each call to `onBindViewHolder`, the button will retain the state from the last contact that was displayed in its `ViewHolder`.
This can be demonstrated by scrolling to the bottom of the list and back up. Enabled buttons at the top of the list will now be disabled.
```java
// In Contact.java
@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {
Contact contact = mContacts.get(position);
TextView textView = viewHolder.nameTextView;
textView.setText(contact.getName());
Button button = viewHolder.messageButton;
if (contact.isOnline()) {
button.setText("Message");
// OMIT to show that rows are recycled.
//
// Scrolling past the midpoint of the list (when contacts are listed as offline)
// and scrolling back up should result in some buttons being inadvertently disabled.
button.setEnabled(true);
}
else {
button.setText("Offline");
button.setEnabled(false);
}
}
```
### Notifying the adapter that the UI must be updated due to dataset changes
Without the call to `notifyItemRangeInserted`, the UI will not reflect the additional contacts that have been appended to the contact list.
```java
// In Contact.java
public void addMoreContacts(List newContacts) {
int insertionPosition = mContacts.size();
mContacts.addAll(newContacts);
// OMIT to illustrate how the UI is independent from the dataset
// and does not update automatically.
notifyItemRangeInserted(insertionPosition, newContacts.size());
}
```
