通用ExpandableListViewAdapter封装

本文介绍了一种针对ExpandableListView的通用BaseAdapter封装方法，通过这种方式，开发者可以在不直接继承BaseExpandableListView或重写其方法的情况下，轻松创建适配器。这种方法不仅简化了代码，还提高了组件的复用性，支持ExpandableListView和普通的ListView。

项目源码已托管在GitHub上，链接如下：

https://github.com/crook3/ExpandableListviewAdapter

使用方法:

在项目的build.gradle文件中添加依赖：

implementation 'com.tranwon:expandablelistview:1.0.1'

在Android应用开发中，ListView是使用频率较高的控件之一。通常情况下，为了实现ListView的功能，开发者需要自定义BaseAdapter，并重写其中的方法。当一个应用中包含多个ListView时，这种重复的工作量会显著增加，导致代码冗余。为此，许多开发者选择封装通用的BaseAdapter，以减少重复劳动。

例如：https://github.com/hongyangAndroid/baseAdapter

基于类似的需求，当应用中需要使用到ExpandableListView（一种支持二级列表显示的控件）时，我们可以自定义一个BaseExpandableListViewAdapter，避免多次重复编写相同的方法。这个封装后的适配器，可以让开发者只需几行代码就能完成配置，极大地简化了工作流程。

原理简介

1. 封装ViewHolder

public class MyViewHolderExpandbleListView {
    private SparseArray mViews;
    private int mPosition;
    private View mConvertView;

    public MyViewHolderExpandbleListView(Context context, ViewGroup parent, int layoutId, int position) {
        this.mPosition = position;
        this.mViews = new SparseArray<>();
        mCOnvertView= LayoutInflater.from(context).inflate(layoutId, parent, false);
        mConvertView.setTag(this);
    }

    public static MyViewHolderExpandbleListView get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {
        if (cOnvertView== null) {
            return new MyViewHolderExpandbleListView(context, parent, layoutId, position);
        } else {
            MyViewHolderExpandbleListView holder = (MyViewHolderExpandbleListView) convertView.getTag();
            holder.mPosition = position;
            return holder;
        }
    }
    public  T getView(int viewId) {
        View view = mViews.get(viewId);
        if (view == null) {
            view = mConvertView.findViewById(viewId);
            mViews.put(viewId, view);
        }
        return (T) view;
    }
    public View getConvertView() {
        return mConvertView;
    }
}

2. 继承BaseExpandableListAdapter进行封装

protected Context mContext;
protected List mDatasParent;
protected List mDatasChild;
protected LayoutInflater mInflater;
private int mLayoutIdParent;
private int mLayoutIdChild;

public MyBaseAdapterExpandbleListview(Context context, List datasParent, List datasChild, int layoutIdParent, int layoutIdChild) {
    this.mCOntext= context;
    mInflater = LayoutInflater.from(context);
    this.mDatasParent = datasParent;
    this.mDatasChild = datasChild;
    this.mLayoutIdParent = layoutIdParent;
    this.mLayoutIdChild = layoutIdChild;
}

@Override
public int getGroupCount() {
    return mDatasParent.size();
}

@Override
public int getChildrenCount(int groupPosition) {
    return 1;
}

@Override
public T getGroup(int groupPosition) {
    return mDatasParent.get(groupPosition);
}

@Override
public T getChild(int groupPosition, int childPosition) {
    return mDatasChild.get(childPosition);
}

@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}

@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
    MyViewHolderExpandbleListView holder = MyViewHolderExpandbleListView.get(mContext, convertView, parent, mLayoutIdParent, groupPosition);
    convertParent(holder, getGroup(groupPosition));
    return holder.getConvertView();
}

@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
    MyViewHolderExpandbleListView holder = MyViewHolderExpandbleListView.get(mContext, convertView, parent, mLayoutIdChild, childPosition);
    convertChild(holder, getChild(groupPosition, childPosition));
    return holder.getConvertView();
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return false;
}

public abstract void convertParent(MyViewHolderExpandbleListView holder, T item);
public abstract void convertChild(MyViewHolderExpandbleListView holder, T item);

3. 使用示例

通过继承CommonAdapter并覆写convert方法，可以非常方便地使用这个适配器。例如，对于ExpandableListView的使用，可以参考以下代码：

MyBaseAdapterExpandbleListview adapter = new MyBaseAdapterExpandbleListview<>(
            getApplicationContext(),
            mListParentData,
            mListChildData,
            R.layout.item_parent,
            R.layout.item_child) {
        @Override
        public void convertParent(MyViewHolderExpandbleListView holder, String item, int parentPosition) {
            TextView tv = holder.getView(R.id.tv1);
            tv.setText(item);
        }

        @Override
        public void convertChild(MyViewHolderExpandbleListView holder, String item, int parentPosition, int childPosition) {
            TextView tv = holder.getView(R.id.tv1);
            tv.setText(item);
        }
    };

对于ListView的使用，可以参考以下代码：

MyBaseAdapterListview adapter = new MyBaseAdapterListview<>(
            getApplicationContext(),
            mListData,
            R.layout.listview_item) {
        @Override
        public void convert(MyViewHolderExpandbleListView holder, String item) {
            TextView tv = holder.getView(R.id.tv1);
            tv.setText(item);
            ImageView im = holder.getView(R.id.image);
            im.setImageResource(R.mipmap.ic_launcher);
        }
    };