Android适配器RecyclerView.Adapter和ArrayAdapter的使用

适配器有什么用？

简单来说就是连接View和数据的桥梁。

如果用MVC模式来理解的话，可以这么理解：

Model(我们的数据) ---> Controller(适配器Adapter)---> View(Android用户界面)

RecyclerView.Adapter（RecyclerView）

Android 5.0时提供了RecyclerView这个列表元件，作为ListView的强化版，它提供更好的效能表现、更高的灵活性，博客有文章将其称为艺术般的元件。

RecyclerView要求必须使用ViewHolder模式，一般我们在使用过程中，都需要去建立一个新的ViewHolder然后作为泛型传入Adapter。

简单的Demo

先写一个MenuProgressAdapter的RecyclerView适配器：

public class MenuProgressAdapter extends RecyclerView.Adapter<MenuProgressAdapter.ViewHolder> {    private Context context;    private List<MenuProgress> data;    private DebugTaskModel debugTask;    public MenuProgressAdapter(Context context, List<MenuProgress> data, DebugTaskModel debugTask) {        this.context = context;        this.data = data;        this.debugTask = debugTask;    }    @Override    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext())                .inflate(R.layout.common_item_list, parent, false);        return new ViewHolder(view);    }    @Override    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {        MenuProgress menuProgress = data.get(position);        holder.menuProgressItem = menuProgress;        holder.itemId.setText(data.get(position).getId());        holder.itemName.setText(data.get(position).getTitle());        if (menuProgress.isFinish()) {            holder.testFinish.setVisibility(View.VISIBLE);            holder.testTodo.setVisibility(View.GONE);        } else {            holder.testFinish.setVisibility(View.GONE);            holder.testTodo.setVisibility(View.VISIBLE);        }        // 为每个Item添加点击事件        holder.itemView.setOnClickListener(v -> {            if (DoubleClickUtil.doubleClick()) {                Toast.makeText(context, DOUBLE_CLICK_PROMPT, Toast.LENGTH_LONG).show();                return;            }            // 获取被点击之后的MenuProgress            MenuProgress item = data.get(position);            // 点击之后的业务逻辑...        });    }    @Override    public int getItemCount() {        if (data == null) {            return 0;        }        return data.size();    }    public void clear() {        if (data != null) {            data.clear();        }        notifyDataSetChanged();    }    public class ViewHolder extends RecyclerView.ViewHolder {        public final View mView;        public final ImageView testFinish;        public final ImageView testTodo;        public final TextView itemId;        public final TextView itemName;        public MenuProgress menuProgressItem;        public ViewHolder(View view) {            super(view);            this.mView = view;            this.testFinish = itemView.findViewById(R.id.testFinish);            this.testTodo = itemView.findViewById(R.id.testTodo);            this.itemId = itemView.findViewById(R.id.itemId);            this.itemName = itemView.findViewById(R.id.itemName);        }        @Override        public String toString() {            return "ViewHolder{" +                    "mView=" + mView +                    ", itemId=" + itemId +                    ", itemName=" + itemName +                    ", menuProgressItem=" + menuProgressItem +                    '}';        }    }}

private MenuProgressAdapter adapter;

// 通过构造器将我们的数据t.getData()和debugTaskData设置进去adapter = new MenuProgressAdapter(this, t.getData(), debugTaskData);// 设置LayoutManagerbinding.debugTaskList.setLayoutManager(new LinearLayoutManager(this));// 为debugTaskList视图设置适配器binding.debugTaskList.setAdapter(adapter);

ArrayAdapter

ArrayAdapter数组适配器用于绑定格式单一的数据，数据源可以是集合或者数组列表视图(ListView)以垂直的形式列出需要显示的列表项。

ArrayAdapter比较简单，通常会和ListView一起使用，但是现在我们已经很少使用ListView了，被废弃了，现在用的是RecyclerView。

简单的Demo（ListView）

定义CommonMenu的适配器ItemListAdapter：

@Data@Builder@AllArgsConstructor@NoArgsConstructorpublic class CommonMenu {    private String id;    private String title;    // 是否完成此试验数据填写    private boolean finish;}

public class ItemListAdapter extends ArrayAdapter<CommonMenu> {    private int resourceId;    public ItemListAdapter(@NonNull Context context, int resource, @NonNull List<CommonMenu> objects) {        super(context, resource, objects);        resourceId = resource;    }    @NonNull    @Override    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {        CommonMenu item = getItem(position);        View view;        if (convertView == null) {            view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);        } else {            view = convertView;        }        TextView itemId = view.findViewById(R.id.itemId);        TextView itemName = view.findViewById(R.id.itemName);        itemId.setText(item.getId());        itemName.setText(item.getTitle());        return view;    }}

使用ItemListAdapter适配器：

private List<CommonMenu> menuList = new ArrayList<>();

// 在此之前，将从数据库中查询出来的menuList放置到适配器中。ItemListAdapter itemListAdapter = new ItemListAdapter(this, R.layout.common_item_list, menuList);// 将此ListView的View拿到ListView itemListView = findViewById(R.id.tap_switch_item_list_view);// 为ListView设置适配器itemListAdapteritemListView.setAdapter(itemListAdapter);// 为每个item设置监听器itemListView.setOnItemClickListener((parent, view, position, id) -> {    // parent：被点击的AdapterView    // view：被点击的View    // position：适配器中被点击的View的位置，可以通过menuList.get(position)可以获取到被点击的CommonMenu数据    // id：id单击的项目的行ID    // 点击某个item之后的业务逻辑...});

获取被点击的item数据，我举个例子，我先添加一个数据：

menuList.add(CommonMenu.builder()             .id("123456789")             .title("示例1")             .finish(true)             .build());

itemListView.setOnItemClickListener((parent, view, position, id) -> {    // 被点击的CommonMenu数据    CommonMenu commonMenu = menuList.get(position);});

OnItemClickListener的源码：

/** * Interface definition for a callback to be invoked when an item in this * AdapterView has been clicked. */public interface OnItemClickListener {    /**     * Callback method to be invoked when an item in this AdapterView has     * been clicked.     * <p>     * Implementers can call getItemAtPosition(position) if they need     * to access the data associated with the selected item.     *     * @param parent The AdapterView where the click happened.     * @param view The view within the AdapterView that was clicked (this     *            will be a view provided by the adapter)     * @param position The position of the view in the adapter.     * @param id The row id of the item that was clicked.     */    void onItemClick(AdapterView<?> parent, View view, int position, long id);}