写一个RecyclerView的notifyDataSetChanged()的例子
时间: 2024-03-07 08:49:35 浏览: 19
好的,以下是一个简单的 RecyclerView 的 `notifyDataSetChanged()` 的例子:
```java
// 假设已经有一个 RecyclerView 实例,名为 recyclerView
// 然后,我们创建一个 Adapter 实例,并将其设置到 RecyclerView 中
MyAdapter adapter = new MyAdapter(dataList);
recyclerView.setAdapter(adapter);
// 在某个时刻,我们需要更新数据,并通知 RecyclerView 刷新视图
// 首先更新数据
dataList.add(newData);
// 然后,调用 Adapter 的 notifyDataSetChanged() 方法
adapter.notifyDataSetChanged();
```
注意:在调用 `notifyDataSetChanged()` 方法之前,需要先修改数据,否则视图不会刷新。此外,如果只是修改了部分数据,可以考虑使用 `notifyItemChanged()`、`notifyItemInserted()`、`notifyItemRemoved()` 等方法,以获得更好的性能。
相关问题
写一个RecyclerView相册分组的例子
好的,以下是一个简单的RecyclerView相册分组的例子:
1. 首先,在你的布局文件中添加一个RecyclerView和一个TextView用于显示分组标题:
```xml
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="LinearLayoutManager"/>
<TextView
android:id="@+id/group_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="16dp"
android:textSize="18sp"
android:textAppearance="@style/TextAppearance.AppCompat.Headline"/>
```
2. 然后,创建一个相册数据模型类Album:
```java
public class Album {
private String title;
private List<Photo> photos;
public Album(String title, List<Photo> photos) {
this.title = title;
this.photos = photos;
}
public String getTitle() {
return title;
}
public List<Photo> getPhotos() {
return photos;
}
}
```
3. 接下来,创建一个照片数据模型类Photo:
```java
public class Photo {
private String title;
private int imageRes;
public Photo(String title, int imageRes) {
this.title = title;
this.imageRes = imageRes;
}
public String getTitle() {
return title;
}
public int getImageRes() {
return imageRes;
}
}
```
4. 然后,创建一个RecyclerView的Adapter类AlbumAdapter:
```java
public class AlbumAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private List<Album> albums;
public AlbumAdapter(List<Album> albums) {
this.albums = albums;
}
@Override
public int getItemCount() {
return albums.size();
}
@Override
public int getItemViewType(int position) {
return position;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_album, parent, false);
return new AlbumViewHolder(view);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
AlbumViewHolder albumViewHolder = (AlbumViewHolder) holder;
Album album = albums.get(position);
albumViewHolder.title.setText(album.getTitle());
albumViewHolder.photoAdapter.setPhotos(album.getPhotos());
}
private class AlbumViewHolder extends RecyclerView.ViewHolder {
private TextView title;
private RecyclerView photoRecyclerView;
private PhotoAdapter photoAdapter;
public AlbumViewHolder(View itemView) {
super(itemView);
title = itemView.findViewById(R.id.title);
photoRecyclerView = itemView.findViewById(R.id.photo_recycler_view);
photoRecyclerView.setLayoutManager(new GridLayoutManager(itemView.getContext(), 3));
photoAdapter = new PhotoAdapter();
photoRecyclerView.setAdapter(photoAdapter);
}
}
private class PhotoAdapter extends RecyclerView.Adapter<PhotoViewHolder> {
private List<Photo> photos = new ArrayList<>();
public void setPhotos(List<Photo> photos) {
this.photos = photos;
notifyDataSetChanged();
}
@Override
public int getItemCount() {
return photos.size();
}
@Override
public PhotoViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_photo, parent, false);
return new PhotoViewHolder(view);
}
@Override
public void onBindViewHolder(PhotoViewHolder holder, int position) {
Photo photo = photos.get(position);
holder.title.setText(photo.getTitle());
holder.image.setImageResource(photo.getImageRes());
}
}
private class PhotoViewHolder extends RecyclerView.ViewHolder {
private TextView title;
private ImageView image;
public PhotoViewHolder(View itemView) {
super(itemView);
title = itemView.findViewById(R.id.title);
image = itemView.findViewById(R.id.image);
}
}
}
```
5. 最后,在你的Activity或Fragment中设置RecyclerView的Adapter:
```java
List<Album> albums = new ArrayList<>();
// 初始化相册数据
AlbumAdapter adapter = new AlbumAdapter(albums);
recyclerView.setAdapter(adapter);
```
这样,你就可以创建一个简单的RecyclerView相册分组了。
写一个recyclerView类似相册支持多选删除的例子
好的,以下是一个简单的RecyclerView类似相册支持多选删除的例子,使用了Kotlin编写:
1. 首先,我们需要定义一个数据类来存储相册中的图片信息:
```kotlin
data class Photo(val id: Long, val uri: Uri)
```
2. 接着,我们需要创建一个RecyclerView的Adapter来显示相册中的图片列表:
```kotlin
class PhotoAdapter(private val context: Context, private val photos: List<Photo>) :
RecyclerView.Adapter<PhotoAdapter.ViewHolder>() {
private val selectedPhotos = mutableListOf<Photo>()
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val imageView: ImageView = itemView.findViewById(R.id.imageView)
private val checkBox: CheckBox = itemView.findViewById(R.id.checkBox)
fun bind(photo: Photo) {
Glide.with(context)
.load(photo.uri)
.into(imageView)
checkBox.isChecked = selectedPhotos.contains(photo)
itemView.setOnClickListener {
if (selectedPhotos.contains(photo)) {
selectedPhotos.remove(photo)
checkBox.isChecked = false
} else {
selectedPhotos.add(photo)
checkBox.isChecked = true
}
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view =
LayoutInflater.from(parent.context).inflate(R.layout.item_photo, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(photos[position])
}
override fun getItemCount(): Int {
return photos.size
}
fun getSelectedPhotos(): List<Photo> {
return selectedPhotos
}
}
```
在这个Adapter中,我们通过Glide库加载图片,并且通过CheckBox来表示用户是否选择了该图片。同时,我们在ViewHolder中添加了一个点击事件监听器,用于在用户点击图片时更新选中状态。
3. 接下来,我们需要在MainActivity中使用这个Adapter来显示相册中的图片列表:
```kotlin
class MainActivity : AppCompatActivity() {
private lateinit var recyclerView: RecyclerView
private lateinit var adapter: PhotoAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
recyclerView = findViewById(R.id.recyclerView)
recyclerView.layoutManager = GridLayoutManager(this, 3)
val photos = getPhotos()
adapter = PhotoAdapter(this, photos)
recyclerView.adapter = adapter
val deleteButton: Button = findViewById(R.id.deleteButton)
deleteButton.setOnClickListener {
val selectedPhotos = adapter.getSelectedPhotos()
for (photo in selectedPhotos) {
contentResolver.delete(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
"${MediaStore.Images.Media._ID} = ?", arrayOf(photo.id.toString()))
}
adapter.notifyDataSetChanged()
}
}
private fun getPhotos(): List<Photo> {
val photos = mutableListOf<Photo>()
val projection = arrayOf(MediaStore.Images.Media._ID, MediaStore.Images.Media.DATA)
val cursor = contentResolver.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
projection, null, null, "${MediaStore.Images.Media.DATE_ADDED} DESC")
cursor?.use {
val idColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media._ID)
val uriColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.DATA)
while (it.moveToNext()) {
val id = it.getLong(idColumn)
val uri = Uri.parse(it.getString(uriColumn))
photos.add(Photo(id, uri))
}
}
return photos
}
}
```
在这个MainActivity中,我们使用ContentResolver从相册中获取图片列表,并且将其传递给PhotoAdapter来显示。我们还在删除按钮上添加了一个点击事件监听器,以便在用户点击该按钮时删除选中的图片。
这样,我们就完成了一个RecyclerView类似相册支持多选删除的例子。当用户在相册中选中图片后,点击删除按钮即可删除选中的图片。