动画数据更改
如果使用除“notifyDataSetChanged”之外的任何通知方法，RecyclerView 将执行相关动画; 这包括 notifyItemChanged，notifyItemInserted，notifyItemMoved，notifyItemRemoved 等。
适配器应该扩展此类而不是 RecyclerView.Adapter。
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import java.util.List;
public abstract class AnimatedRecyclerAdapter<T, VH extends RecyclerView.ViewHolder>
extends RecyclerView.Adapter<VH> {
protected List<T> models;
protected AnimatedRecyclerAdapter(@NonNull List<T> models) {
this.models = models;
}
//Set new models.
public void setModels(@NonNull final List<T> models) {
applyAndAnimateRemovals(models);
applyAndAnimateAdditions(models);
applyAndAnimateMovedItems(models);
}
//Remove an item at position and notify changes.
private T removeItem(int position) {
final T model = models.remove(position);
notifyItemRemoved(position);
return model;
}
//Add an item at position and notify changes.
private void addItem(int position, T model) {
models.add(position, model);
notifyItemInserted(position);
}
//Move an item at fromPosition to toPosition and notify changes.
private void moveItem(int fromPosition, int toPosition) {
final T model = models.remove(fromPosition);
models.add(toPosition, model);
notifyItemMoved(fromPosition, toPosition);
}
//Remove items that no longer exist in the new models.
private void applyAndAnimateRemovals(@NonNull final List<T> newTs) {
for (int i = models.size() - 1; i >= 0; i--) {
final T model = models.get(i);
if (!newTs.contains(model)) {
removeItem(i);
}
}
}
//Add items that do not exist in the old models.
private void applyAndAnimateAdditions(@NonNull final List<T> newTs) {
for (int i = 0, count = newTs.size(); i < count; i++) {
final T model = newTs.get(i);
if (!models.contains(model)) {
addItem(i, model);
}
}
}
//Move items that have changed their position.
private void applyAndAnimateMovedItems(@NonNull final List<T> newTs) {
for (int toPosition = newTs.size() - 1; toPosition >= 0; toPosition--) {
final T model = newTs.get(toPosition);
final int fromPosition = models.indexOf(model);
if (fromPosition >= 0 && fromPosition != toPosition) {
moveItem(fromPosition, toPosition);
}
}
}
}
你应不使用相同的
List在适配器setModels和List。
你将 models 声明为全局变量。DataModel 只是一个虚拟类。
private List<DataModel> models;
private YourAdapter adapter;
在将 models 传递给适配器之前初始化 models。YourAdapter 是 AnimatedRecyclerAdapter 的实施。
models = new ArrayList<>();
//Add models
models.add(new DataModel());
//Do NOT pass the models directly. Otherwise, when you modify global models,
//you will also modify models in adapter.
//adapter = new YourAdapter(models); <- This is wrong.
adapter = new YourAdapter(new ArrayList(models));
更新全局 models 后调用此方法。
adapter.setModels(new ArrayList(models));
如果你不覆盖
equals，则通过引用比较所有比较。
使用 SortedList 的示例
在介绍了 RecyclerView 之后，Android 很快推出了 SortedList 类。此类处理对 RecyclerView.Adapter 的所有 notify 方法调用以确保正确的动画，甚至允许批量处理多个更改，因此动画不会抖动。
import android.support.v7.util.SortedList;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.util.SortedListAdapterCallback;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private SortedList<DataModel> mSortedList;
class ViewHolder extends RecyclerView.ViewHolder {
TextView text;
CheckBox checkBox;
ViewHolder(View itemView){
super(itemView);
//Initiate your code here...
}
void setDataModel(DataModel model) {
//Update your UI with the data model passed here...
text.setText(modle.getText());
checkBox.setChecked(model.isChecked());
}
}
public MyAdapter() {
mSortedList = new SortedList<>(DataModel.class, new SortedListAdapterCallback<DataModel>(this) {
@Override
public int compare(DataModel o1, DataModel o2) {
//This gets called to find the ordering between objects in the array.
if (o1.someValue() < o2.someValue()) {
return -1;
} else if (o1.someValue() > o2.someValue()) {
return 1;
} else {
return 0;
}
}
@Override
public boolean areContentsTheSame(DataModel oldItem, DataModel newItem) {
//This is to see of the content of this object has changed. These items are only considered equal if areItemsTheSame() returned true.
//If this returns false, onBindViewHolder() is called with the holder containing the item, and the item's position.
return oldItem.getText().equals(newItem.getText()) && oldItem.isChecked() == newItem.isChecked();
}
@Override
public boolean areItemsTheSame(DataModel item1, DataModel item2) {
//Checks to see if these two items are the same. If not, it is added to the list, otherwise, check if content has changed.
return item1.equals(item2);
}
});
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = //Initiate your item view here.
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
//Just update the holder with the object in the sorted list from the given position
DataModel model = mSortedList.get(position);
if (model != null) {
holder.setDataModel(model);
}
}
@Override
public int getItemCount() {
return mSortedList.size();
}
public void resetList(List<DataModel> models) {
//If you are performing multiple changes, use the batching methods to ensure proper animation.
mSortedList.beginBatchedUpdates();
mSortedList.clear();
mSortedList.addAll(models);
mSortedList.endBatchedUpdates();
}
//The following methods each modify the data set and automatically handles calling the appropriate 'notify' method on the adapter.
public void addModel(DataModel model) {
mSortedList.add(model);
}
public void addModels(List<DataModel> models) {
mSortedList.addAll(models);
}
public void clear() {
mSortedList.clear();
}
public void removeModel(DataModel model) {
mSortedList.remove(model);
}
public void removeModelAt(int i) {
mSortedList.removeItemAt(i);
}
}