文章目录
RecyclerView总结
概述
RecyclerView是谷歌官方推出的一个用于大量数据展示的新空间，可以说是一个增强的ListView，优化了ListView的不足之处，更加强大和灵活。
基本实现
列表布局
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(linearLayoutManager);
mAdapter = new FruitAdapter(this, mDatas);
recyclerView.setAdapter(mAdapter);
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private final Context mContext;
private final ArrayList<Fruit> mDatas;
private final LayoutInflater layoutInflater;
public FruitAdapter(Context context, ArrayList<Fruit> datas) {
mContext = context;
mDatas = datas;
layoutInflater = LayoutInflater.from(context);
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = layoutInflater.inflate(R.layout.item_linear_fruit, parent, false);
ViewHolder viewHolder = new ViewHolder(itemView);
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Fruit fruit = mDatas.get(position);
holder.name.setText(fruit.getName());
holder.img.setImageResource(fruit.getImg());
}
@Override
public int getItemCount() {
return mDatas.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
TextView name;
ImageView img;
public ViewHolder(@NonNull View itemView) {
super(itemView);
name = itemView.findViewById(R.id.name);
img = itemView.findViewById(R.id.img);
}
}
}
网格布局
GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 4);
recyclerView.setLayoutManager(gridLayoutManager);
FruitAdapter mAdapter = new FruitAdapter(this, mDatas);
recyclerView.setAdapter(mAdapter);
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private final Context mContext;
private final ArrayList<Fruit> mDatas;
private final LayoutInflater layoutInflater;
public FruitAdapter(Context context, ArrayList<Fruit> datas) {
mContext = context;
mDatas = datas;
layoutInflater = LayoutInflater.from(context);
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = layoutInflater.inflate(R.layout.item_grid_fruit, parent, false);
ViewHolder viewHolder = new ViewHolder(itemView);
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Fruit fruit = mDatas.get(position);
holder.name.setText(fruit.getName());
holder.img.setImageResource(fruit.getImg());
}
@Override
public int getItemCount() {
return mDatas.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
TextView name;
ImageView img;
public ViewHolder(@NonNull View itemView) {
super(itemView);
name = itemView.findViewById(R.id.name);
img = itemView.findViewById(R.id.img);
}
}
}
瀑布流布局
StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(staggeredGridLayoutManager);
FruitAdapter mAdapter = new FruitAdapter(this, mDatas);
recyclerView.setAdapter(mAdapter);
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private final Context mContext;
private final ArrayList<Fruit> mDatas;
private final LayoutInflater layoutInflater;
public FruitAdapter(Context context, ArrayList<Fruit> datas) {
mContext = context;
mDatas = datas;
layoutInflater = LayoutInflater.from(context);
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = layoutInflater.inflate(R.layout.item_fruit_desc, parent, false);
ViewHolder viewHolder = new ViewHolder(itemView);
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Fruit fruit = mDatas.get(position);
holder.name.setText(fruit.getName());
holder.img.setImageResource(fruit.getImg());
holder.desc.setText(fruit.getDesc());
}
@Override
public int getItemCount() {
return mDatas.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
TextView name;
ImageView img;
TextView desc;
public ViewHolder(@NonNull View itemView) {
super(itemView);
name = itemView.findViewById(R.id.name);
img = itemView.findViewById(R.id.img);
desc = itemView.findViewById(R.id.desc);
}
}
}
设置分割线
ItemDecoration类介绍
RecyclerView中的分割线通继承RecyclerView.ItemDecoration类实现，ItemDecoration中有3个方法：
- getItemOffsets(): 设置itemView的偏移量。
- onDraw(): 通过Canvas绘制分割线内容，ItemDecoration的
onDraw()早于itemView的onDraw()执行。 - onDrawOver(): 与
onDraw()类似，在itemView的onDraw()之后执行。
基本实现
列表布局中的分割线
public class LinearItemDecoration extends RecyclerView.ItemDecoration {
//RecyclerView布局方向
private int mOrientation = LinearLayoutManager.VERTICAL;
//分割线大小
private int mDividerSize = 1;
//分割线颜色
private int mColor = Color.RED;
//Drawable分割线
private Drawable mDividerDrawable;
private Paint mPaint;
private final Context mContext;
/**
* @param context
* @param orientation 列表方向
* @param color 颜色
* @param dividerSize 分割线大小
*/
public LinearItemDecoration(Context context, int orientation, int color, int dividerSize) {
mContext = context;
mOrientation = orientation;
mColor = color;
mDividerSize = dividerSize;
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(mColor);
mPaint.setStyle(Paint.Style.FILL);
}
public LinearItemDecoration(Context context, int orientation, int drawableId) {
mContext = context;
mOrientation = orientation;
mDividerDrawable = ContextCompat.getDrawable(context, drawableId);
mDividerSize = mDividerDrawable.getIntrinsicHeight();
}
//设置分割线颜色
public void setColor(int color) {
mPaint.setColor(color);
}
//设置分割线大小
public void setDividerSize(int size) {
mDividerSize = size;
}
/**
* 设置分割线大小
*/
@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
if (mOrientation == LinearLayout.VERTICAL) {
outRect.set(0, 0, 0, mDividerSize);
} else {
outRect.set(0, 0, mDividerSize, 0);
}
}
/**
* 绘制分割线
*/
@Override
public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
if (mOrientation == LinearLayout.VERTICAL) {
drawVertical(c, parent);
} else {
drawHorizontal(c, parent);
}
}
/**
* 垂直方向分割线绘制
*/
private void drawVertical(@NonNull Canvas c, @NonNull RecyclerView parent) {
final int left = parent.getPaddingLeft();
final int right = parent.getMeasuredWidth() - parent.getPaddingRight();
final int childSize = parent.getChildCount();
for (int i = 0; i < childSize; i++) {
final View childView = parent.getChildAt(i);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) childView.getLayoutParams();
final int top = childView.getBottom() + layoutParams.bottomMargin;
final int bottom = top + mDividerSize;
if (mDividerDrawable == null) {
c.drawRect(left, top, right, bottom, mPaint);
} else {
mDividerDrawable.setBounds(left, top, right, bottom);
mDividerDrawable.draw(c);
}
}
}
/**
* 水平方向分割线绘制
*/
private void drawHorizontal(@NonNull Canvas c, @NonNull RecyclerView parent) {
final int top = parent.getPaddingTop();
final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();
final int childSize = parent.getChildCount();
for (int i = 0; i < childSize; i++) {
final View childView = parent.getChildAt(i);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) childView.getLayoutParams();
final int left = childView.getRight() + layoutParams.rightMargin;
final int right = left + mDividerSize;
if (mDividerDrawable == null) {
c.drawRect(left, top, right, bottom, mPaint);
} else {
mDividerDrawable.setBounds(left, top, right, bottom);
mDividerDrawable.draw(c);
}
}
}
}
//LinearItemDecoration linearItemDecoration = new LinearItemDecoration(this, LinearLayoutManager.VERTICAL, Color.BLACK, 1);
//或
LinearItemDecoration linearItemDecoration = new LinearItemDecoration(this, LinearLayoutManager.VERTICAL, R.drawable.shap_divider);
recyclerView.addItemDecoration(linearItemDecoration);
网格布局中的分割线
与列表布局中的分割线基本类似
public class GridItemDecoration extends RecyclerView.ItemDecoration {
private int mDividerSize = 10;
private Paint mPaint;
private final Context mContext;
public GridItemDecoration(Context context) {
mContext = context;
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(Color.RED);
mPaint.setStyle(Paint.Style.FILL);
}
public void setColor(int color) {
mPaint.setColor(color);
}
/**
* 获取RecyclerView列数
*/
private int getSpanCount(RecyclerView parent) {
int spanCount = -1;
GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
spanCount = layoutManager.getSpanCount();
return spanCount;
}
/**
* 是否最后一列
*/
private boolean isLastColumn(RecyclerView parent, int position, int spanCount, int childCount) {
if ((position + 1) % spanCount == 0) {
return true;
} else {
return false;
}
}
/**
* 是否最后一行
*/
private boolean isLastRow(RecyclerView parent, int position, int spanCount, int childCount) {
childCount = childCount - childCount % spanCount;
if (position >= childCount) {
return true;
} else {
return false;
}
}
/**
* 设置分割线大小
*/
@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
int spanCount = getSpanCount(parent);
int childCount = parent.getAdapter().getItemCount();
int position = parent.getChildAdapterPosition(view);
if (isLastRow(parent, position, spanCount, childCount)) {
//最后一行不绘制底部
outRect.set(0, 0, mDividerSize, 0);
} else if (isLastColumn(parent, position, spanCount, childCount)) {
//最后一列不绘制右边
outRect.set(0, 0, 0, mDividerSize);
} else {
outRect.set(0, 0, mDividerSize, mDividerSize);
}
}
/**
* 绘制分割线
*/
@Override
public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
drawVertical(c, parent);
drawHorizontal(c, parent);
}
/**
* 绘制垂直分割线
*/
private void drawVertical(@NonNull Canvas c, @NonNull RecyclerView parent) {
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View childView = parent.getChildAt(i);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) childView.getLayoutParams();
final int left = childView.getRight() + layoutParams.rightMargin;
final int top = childView.getTop() - layoutParams.topMargin;
final int right = left + mDividerSize;
final int bottom = childView.getBottom() + layoutParams.bottomMargin;
c.drawRect(left, top, right, bottom, mPaint);
}
}
/**
* 绘制水平分割线
*/
private void drawHorizontal(@NonNull Canvas c, @NonNull RecyclerView parent) {
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View childView = parent.getChildAt(i);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) childView.getLayoutParams();
fnal int left = childView.getLeft() - layoutParams.leftMargin;
final int top = childView.getBottom() + layoutParams.bottomMargin;
final int right = childView.getRight() + layoutParams.rightMargin + mDividerSize;
final int bottom = top + mDividerSize;
c.drawRect(left, top, right, bottom, mPaint);
}
}
}
recyclerView.addItemDecoration(new GridItemDecoration(this));
数据增删改操作
//增加数据
//指定位置添加一个数据
void notifyItemInserted(int position)
//指定位置添加多个数据
void notifyItemRangeInserted(int positionStart, int itemCount)
//删除数据
//删除指定位置的一个数据
void notifyItemRemoved(int position)
//删除指定位置的多个数据
void notifyItemRangeRemoved(int positionStart, int itemCount)
//修改数据
//修改指定位置的数据
void notifyItemChanged(int position)
//修改指定位置的多个数据
void notifyItemRangeChanged(int positionStart, int itemCount)
//刷新列表
void void notifyDataSetChanged()
DiffUtil的使用
在实际开发中，可能需要修改多个数据源，这是需要直接调用notifyDataSetChanged()更新列表，但使用notifyDataSetChanged()存在一些缺点，如：不会触发动画、性能偏低，这时可以借助DiffUtil。
DiffUtil适用于比较两个数据源，计算它们之间的差值，然后进行定制操作。
基本实现
public class AdapterDiffCallback extends DiffUtil.Callback {
private ArrayList<User> mOldList;
private ArrayList<User> mNewList;
public AdapterDiffCallback(ArrayList<User> oldList, ArrayList<User> newList) {
mOldList = oldList;
mNewList = newList;
}
@Override
public int getOldListSize() {
return mOldList.size();
}
@Override
public int getNewListSize() {
return mNewList.size();
}
/**
* 判断是否同一个item
*/
@Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return mOldList.get(oldItemPosition).getId() == mNewList.get(newItemPosition).getId();
}
/**
* 比较两个item的内容是否相同
*/
@Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
String oldName = mOldList.get(oldItemPosition).getName();
String oldAddress = mOldList.get(oldItemPosition).getAddress();
int oldAge = mOldList.get(oldItemPosition).getAge();
String newName = mNewList.get(newItemPosition).getName();
String newAddress = mNewList.get(newItemPosition).getAddress();
int newAge = mNewList.get(newItemPosition).getAge();
return oldAddress.equals(newAddress) && oldName.equals(newName) && oldAge == newAge;
}
}
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
public void setDatas(ArrayList<User> datas) {
DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new AdapterDiffCallback(mDatas, datas), true);
diffResult.dispatchUpdatesTo(this);
//更新数据源，必须放在dispatchUpdatesTo之后
mDatas = datas;
}
}
使用
ArrayList<User> newDatas = new ArrayList<>();
for (User user : mDatas) {
newDatas.add(user.clone());
}
newDatas.get(3).setAge(333333);
newDatas.get(3).setAddress("6666666");
newDatas.remove(0);
newDatas.add(new User(18, "新姓名18", 18, "新地址18"));
mAdapter.setDatas(newDatas);