文章目錄

RecyclerView總結
- 概述
- 基本實作
- - 串列布局
  - 網格布局
  - 瀑布流布局
- 設定分割線
- - ItemDecoration類介紹
  - 基本實作
  - - 串列布局中的分割線
    - 網格布局中的分割線
- 資料增刪改操作
- DiffUtil的使用
- 代碼下載

RecyclerView總結

概述

RecyclerView是谷歌官方推出的一個用于大量資料展示的新空間，可以說是一個增強的ListView，優化了ListView的不足之處，更加強大和靈活，

基本實作

串列布局

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);
        }
    }
}

網格布局

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);
        }
    }
}

設定分割線

ItemDecoration類介紹

RecyclerView中的分割線通繼承RecyclerView.ItemDecoration類實作，ItemDecoration中有3個方法：

getItemOffsets(): 設定itemView的偏移量，
onDraw(): 通過Canvas繪制分割線內容，ItemDecoration的onDraw()早于itemView的onDraw()執行，
onDrawOver(): 與onDraw()類似，在itemView的onDraw()之后執行，

基本實作

串列布局中的分割線

public class LinearItemDecoration extends RecyclerView.ItemDecoration {
    //RecyclerView布局方向
    private int mOrientation = LinearLayoutManager.VERTICAL;
    //分割線大小
    private int mDividerSize = 1;
    //分割線顏色
    private int mColor = Color.RED;
    //Drawable分割線
    private Drawable mDividerDrawable;

    private Paint mPaint;
    private final Context mContext;

    /**
     * @param context
     * @param orientation 串列方向
     * @param color       顏色
     * @param dividerSize 分割線大小
     */
    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();
    }

    //設定分割線顏色
    public void setColor(int color) {
        mPaint.setColor(color);
    }

    //設定分割線大小
    public void setDividerSize(int size) {
        mDividerSize = size;
    }

    /**
     * 設定分割線大小
     */
    @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);
        }
    }

    /**
     * 繪制分割線
     */
    @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);
        }
    }

    /**
     * 垂直方向分割線繪制
     */
    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);
            }
        }
    }

    /**
     * 水平方向分割線繪制
     */
    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);

網格布局中的分割線

與串列布局中的分割線基本類似

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);
    }

    /**
     * 獲取RecyclerView列數
     */
    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;
        }
    }

    /**
     * 設定分割線大小
     */
    @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)) {
            //最后一行不繪制底部
            outRect.set(0, 0, mDividerSize, 0);
        } else if (isLastColumn(parent, position, spanCount, childCount)) {
            //最后一列不繪制右邊
            outRect.set(0, 0, 0, mDividerSize);
        } else {
            outRect.set(0, 0, mDividerSize, mDividerSize);
        }
    }

    /**
     * 繪制分割線
     */
    @Override
    public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        drawVertical(c, parent);
        drawHorizontal(c, parent);
    }

    /**
     * 繪制垂直分割線
     */
    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);
        }
    }

    /**
     * 繪制水平分割線
     */
    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));

資料增刪改操作

//增加資料
//指定位置添加一個資料
void notifyItemInserted(int position)
//指定位置添加多個資料
void notifyItemRangeInserted(int positionStart, int itemCount)

//洗掉資料
//洗掉指定位置的一個資料
void notifyItemRemoved(int position)
//洗掉指定位置的多個資料
void notifyItemRangeRemoved(int positionStart, int itemCount) 

//修改資料
//修改指定位置的資料
void notifyItemChanged(int position) 
//修改指定位置的多個資料
void notifyItemRangeChanged(int positionStart, int itemCount)

//重繪串列
void void notifyDataSetChanged()

DiffUtil的使用

在實際開發中，可能需要修改多個資料源，這是需要直接呼叫notifyDataSetChanged()更新串列，但使用notifyDataSetChanged()存在一些缺點，如：不會觸發影片、性能偏低，這時可以借助DiffUtil，

DiffUtil適用于比較兩個資料源，計算它們之間的差值，然后進行定制操作，

基本實作

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();
    }

    /**
     * 判斷是否同一個item
     */
    @Override
    public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
        return mOldList.get(oldItemPosition).getId() == mNewList.get(newItemPosition).getId();
    }

    /**
     * 比較兩個item的內容是否相同
     */
    @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);
        //更新資料源，必須放在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);

代碼下載

https://github.com/xiangxiongfly/RecyclerViewDemo

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Android RecyclerView總結

文章目錄

RecyclerView總結

概述

基本實作

串列布局

網格布局

瀑布流布局

設定分割線

ItemDecoration類介紹

基本實作

串列布局中的分割線

網格布局中的分割線

資料增刪改操作

DiffUtil的使用

代碼下載