在 RecyclerView 中膨胀两种类型的 .XML

Question

由于我遇到的一个问题，我感到非常沮丧：如何为 RecyclerView 中的不同对象扩展不同的 .XML 文件？我已经做了力所能及的事了，比如制作一个 ListItemType 对象：

public class ListItemType {
    public static int NOTE_VIEW = 0;
    public static int CATEGORY_VIEW = 1;
}

还有一个 ListViewItem 对象：

public class ListViewItem {
    private int mType;
    private Object mObject;

    public ListViewItem(int type, Object object) {
        mType = type;
        mObject = object;
    }

    public int getType() {
        return mType;
    }

    public void setType(int type) {
        mType = type;
    }

    public Object getObject() {
        return mObject;
    }

    public void setObject(Object object) {
        mObject = object;
    }
}

我不知道我从这里去哪里。

Answer 1

RecyclerView 实现

首先，您必须添加/创建到/您的Model 类型以指示您的Model 类型，并知道要膨胀哪个布局：

MyModel.java

public class MyModel {
    public enum ModelTypes {
        TYPE_1,
        TYPE_2
    }
    // your model members ^^^

    ModelTypes type;
}

现在你必须创建你的ViewHolder，我建议创建一个父ViewHolder 类并使用子类扩展你的模型类型。

MyHolder.java

public class MyHolder extends RecyclerView.ViewHolder {

    // must have the ViewHolder default constructor
    public MyHolder(View itemView) {
        super(itemView);
    }

    public static MyHolder inflateViewByType(MyModel.ModelTypes type, 
                                            LayoutInflater layoutInflater, ViewGroup parent) {
        View view;
        switch (type) {
            case TYPE_1:
                view = layoutInflater.inflate(R.layout.layout_type_1, parent, false);
                return new MyHolderType1(view);
            break;
            case TYPE_2:
                view = layoutInflater.inflate(R.layout.layout_type_2, parent, false);
                return new MyHolderType2(view);
            break;
        }
        // Model type not supported
        return null;
    }
}

创建您的 ViewHolder 类型，在我的示例中，我只有两种类型。

MyHolderType1.java

public class MyHolderType1 extends MyHolder {

    // layout members

    public MyHolderType1(View itemView) {
        super(itemView);
        // init your layout members by for layout_type_1 by itemView.findViewById(...)
    }
}

MyHolderType2.java

public class MyHolderType2 extends MyHolder {

    // layout members

    public MyHolderType2(View itemView) {
        super(itemView);
        // init your layout members by for layout_type_2 by itemView.findViewById(...)
    }
}

到目前为止，您只能创建 ViewHolder 类型来实现 RecyclerView。 RecyclerView 必须有一个扩展默认 RecyclerView.Adapter 的 Adapter，为此我们必须创建一个新类并使用我们的 ViewHolder 扩展 RecyclerView.Adapter。

MyRecyclerViewAdapter.java

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyHolder> {

    private List<MyModel> mData;

    public MyRecyclerViewAdapter(@NonNull List<MyModel> data) {
        mData = data;
    }

    @Override
    public MyHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        MyModel.ModelTypes type = MyModel.ModelTypes.values()[viewType];
        return MyHolder.inflateViewByType(type, layoutInflater, parent);
    }

    @Override
    public void onBindViewHolder(MyHolder holder, int position) {

        MyModel model = mData.get(position);
        switch (model.type) {
            case TYPE_1:
                setupViewType1((MyHolderType1) holder, model);
                break;
            case TYPE_2:
                setupViewType2((MyHolderType2) holder, model);
                break;
        }
    }

    // to update the adapter data without reinitialize it
    public void updateData(@NonNull List<MyModel> newData) {
        mData = newData;
        notifyDataSetChanged();
    }

    private void setupViewType1(MyHolderType1 holder, MyModel model) {

        // do what you want with your views in layout_type_1
    }

    private void setupViewType2(MyHolderType2 holder, MyModel model) {

        // do what you want with your views in layout_type_2
    }

    @Override
    public int getItemCount() {
        return mData.size();
    }

    @Override
    public int getItemViewType(int position) {
        return mData.get(position).type.ordinal();
    }
}

继续，我们差不多完成了。 现在我们必须在我们的活动中初始化RecyclerView，并将MyRecyclerViewAdapter 的实例设置为它。 为此我们通过调用findViewById(...)在和xml中找到RecyclerView，然后将LayoutManager设置为RecyclerView，毕竟我们用我们的数据设置了适配器。

MyActivity.java

public class MyActivity extends Activity{

    // ....

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_layout);


        // init your views
        RecyclerView recyclerView = findViewById(R.id.recycler_view);


        // here you can pull or generate your recycler view list data
        List<MyModel> data = getData();
        MyRecyclerViewAdapter adapter = new MyRecyclerViewAdapter(data);


        // set layout manager to the recycler view (Required)
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, 
                                                        LinearLayoutManager.VERTICAL, false);
        recyclerView.setLayoutManager(linearLayoutManager);

        // set the adapter to the recycler view (Required)
        recyclerView.setAdapter(adapter);
    }

    // ....
}