Android 中 RecyclerView 4级嵌套
时间: 2023-11-16 21:40:09 浏览: 37
在 Android 中,RecyclerView 支持嵌套使用,但是四级嵌套可能会导致性能问题,建议尽量避免这种情况。
如果确实需要四级嵌套,可以考虑以下几点优化:
1. 确认是否真的需要四级嵌套,能否通过其他方式实现同样的效果。
2. 尽量避免使用 wrap_content,因为这会导致测量过程变得复杂,可以使用具体的尺寸或者 match_parent。
3. 使用 RecyclerView.ViewHolder 的缓存机制来提高性能。
4. 注意 RecyclerView 的 item 复用机制,确保重复使用 item,而不是每次都创建新的 item。
5. 如果 RecyclerView 中的 item 也是 RecyclerView,可以重写 RecyclerView.RecycledViewPool 来进行缓存。
相关问题
Android 中 RecyclerView 4级嵌套例程
在 Android 中,RecyclerView 的嵌套使用也是比较常见的,可以实现复杂的列表布局。下面是一个四级嵌套的例程:
1. 创建四个不同的 RecyclerView.Adapter
首先,我们需要创建四个不同的 RecyclerView.Adapter,分别是最外层、第二层、第三层和最内层的 Adapter。
最外层Adapter的代码示例:
```java
public class OuterAdapter extends RecyclerView.Adapter<OuterAdapter.OuterViewHolder> {
private List<SecondAdapter> mSecondAdapters;
public OuterAdapter(List<SecondAdapter> secondAdapters) {
mSecondAdapters = secondAdapters;
}
@NonNull
@Override
public OuterViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_outer, parent, false);
return new OuterViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull OuterViewHolder holder, int position) {
holder.bind(mSecondAdapters.get(position));
}
@Override
public int getItemCount() {
return mSecondAdapters.size();
}
static class OuterViewHolder extends RecyclerView.ViewHolder {
private RecyclerView mSecondRecyclerView;
OuterViewHolder(@NonNull View itemView) {
super(itemView);
mSecondRecyclerView = itemView.findViewById(R.id.second_recycler_view);
mSecondRecyclerView.setLayoutManager(new LinearLayoutManager(itemView.getContext()));
}
void bind(SecondAdapter adapter) {
mSecondRecyclerView.setAdapter(adapter);
}
}
}
```
第二层、第三层和最内层的 Adapter 代码类似,只需要根据对应的布局和数据类型进行修改即可。
2. 在最外层 RecyclerView 中设置第二层 Adapter
在最外层 RecyclerView 中,我们需要将第二层的 Adapter 设置到对应的 ViewHolder 中。
最外层 RecyclerView 的代码示例:
```java
public class MainActivity extends AppCompatActivity {
private RecyclerView mOuterRecyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mOuterRecyclerView = findViewById(R.id.outer_recycler_view);
mOuterRecyclerView.setLayoutManager(new LinearLayoutManager(this));
List<SecondAdapter> secondAdapters = new ArrayList<>();
for (int i = 0; i < 10; i++) {
SecondAdapter secondAdapter = new SecondAdapter();
secondAdapters.add(secondAdapter);
}
OuterAdapter outerAdapter = new OuterAdapter(secondAdapters);
mOuterRecyclerView.setAdapter(outerAdapter);
}
}
```
3. 在第二层 RecyclerView 中设置第三层 Adapter
在第二层 RecyclerView 中,我们需要将第三层的 Adapter 设置到对应的 ViewHolder 中。同样地,在第三层 RecyclerView 中设置最内层的 Adapter。
第二层 RecyclerView 的代码示例:
```java
public class SecondAdapter extends RecyclerView.Adapter<SecondAdapter.SecondViewHolder> {
private List<ThirdAdapter> mThirdAdapters;
public SecondAdapter() {
mThirdAdapters = new ArrayList<>();
for (int i = 0; i < 5; i++) {
ThirdAdapter thirdAdapter = new ThirdAdapter();
mThirdAdapters.add(thirdAdapter);
}
}
@NonNull
@Override
public SecondViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_second, parent, false);
return new SecondViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull SecondViewHolder holder, int position) {
holder.bind(mThirdAdapters.get(position));
}
@Override
public int getItemCount() {
return mThirdAdapters.size();
}
static class SecondViewHolder extends RecyclerView.ViewHolder {
private RecyclerView mThirdRecyclerView;
SecondViewHolder(@NonNull View itemView) {
super(itemView);
mThirdRecyclerView = itemView.findViewById(R.id.third_recycler_view);
mThirdRecyclerView.setLayoutManager(new LinearLayoutManager(itemView.getContext()));
}
void bind(ThirdAdapter adapter) {
mThirdRecyclerView.setAdapter(adapter);
}
}
}
```
4. 在第三层 RecyclerView 中设置最内层 Adapter
第三层 RecyclerView 的代码示例:
```java
public class ThirdAdapter extends RecyclerView.Adapter<ThirdAdapter.ThirdViewHolder> {
private List<String> mItems;
public ThirdAdapter() {
mItems = new ArrayList<>();
for (int i = 0; i < 3; i++) {
mItems.add("Item " + i);
}
}
@NonNull
@Override
public ThirdViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_third, parent, false);
return new ThirdViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull ThirdViewHolder holder, int position) {
holder.bind(mItems.get(position));
}
@Override
public int getItemCount() {
return mItems.size();
}
static class ThirdViewHolder extends RecyclerView.ViewHolder {
private TextView mTextView;
ThirdViewHolder(@NonNull View itemView) {
super(itemView);
mTextView = itemView.findViewById(R.id.text_view);
}
void bind(String item) {
mTextView.setText(item);
}
}
}
```
以上就是 RecyclerView 四级嵌套的例程,如果需要更多嵌套层级,可以按照同样的方式进行扩展。
Android 中 RecyclerView 3级嵌套例程
RecyclerView 的三级嵌套可以使用多个 RecyclerView 来实现,每个 RecyclerView 对应一个嵌套的层级。
示例代码如下:
1. 定义三个 RecyclerView,分别对应三级嵌套的层级。
```
private RecyclerView recyclerView1;
private RecyclerView recyclerView2;
private RecyclerView recyclerView3;
```
2. 初始化 RecyclerView,设置布局管理器和适配器。
```
recyclerView1 = findViewById(R.id.recyclerView1);
recyclerView1.setLayoutManager(new LinearLayoutManager(this));
recyclerView1.setAdapter(new MyAdapter1());
recyclerView2 = findViewById(R.id.recyclerView2);
recyclerView2.setLayoutManager(new LinearLayoutManager(this));
recyclerView2.setAdapter(new MyAdapter2());
recyclerView3 = findViewById(R.id.recyclerView3);
recyclerView3.setLayoutManager(new LinearLayoutManager(this));
recyclerView3.setAdapter(new MyAdapter3());
```
3. 实现每个 RecyclerView 的适配器。
```
private class MyAdapter1 extends RecyclerView.Adapter<MyViewHolder1> {
@NonNull
@Override
public MyViewHolder1 onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_level1, parent, false);
return new MyViewHolder1(view);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder1 holder, int position) {
// 绑定数据
}
@Override
public int getItemCount() {
return 10;
}
}
private class MyViewHolder1 extends RecyclerView.ViewHolder {
public MyViewHolder1(@NonNull View itemView) {
super(itemView);
}
}
private class MyAdapter2 extends RecyclerView.Adapter<MyViewHolder2> {
@NonNull
@Override
public MyViewHolder2 onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_level2, parent, false);
return new MyViewHolder2(view);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder2 holder, int position) {
// 绑定数据
}
@Override
public int getItemCount() {
return 5;
}
}
private class MyViewHolder2 extends RecyclerView.ViewHolder {
public MyViewHolder2(@NonNull View itemView) {
super(itemView);
}
}
private class MyAdapter3 extends RecyclerView.Adapter<MyViewHolder3> {
@NonNull
@Override
public MyViewHolder3 onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_level3, parent, false);
return new MyViewHolder3(view);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder3 holder, int position) {
// 绑定数据
}
@Override
public int getItemCount() {
return 3;
}
}
private class MyViewHolder3 extends RecyclerView.ViewHolder {
public MyViewHolder3(@NonNull View itemView) {
super(itemView);
}
}
```
4. 在前一个 RecyclerView 的适配器中,给每个 item 添加点击事件,根据点击的位置切换到下一个 RecyclerView。
```
private class MyAdapter1 extends RecyclerView.Adapter<MyViewHolder1> {
...
@Override
public void onBindViewHolder(@NonNull MyViewHolder1 holder, int position) {
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
recyclerView1.setVisibility(View.GONE);
recyclerView2.setVisibility(View.VISIBLE);
}
});
}
}
private class MyAdapter2 extends RecyclerView.Adapter<MyViewHolder2> {
...
@Override
public void onBindViewHolder(@NonNull MyViewHolder2 holder, int position) {
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
recyclerView2.setVisibility(View.GONE);
recyclerView3.setVisibility(View.VISIBLE);
}
});
}
}
private class MyAdapter3 extends RecyclerView.Adapter<MyViewHolder3> {
...
@Override
public void onBindViewHolder(@NonNull MyViewHolder3 holder, int position) {
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// 最后一级嵌套,不需要切换到下一个 RecyclerView
}
});
}
}
```
以上示例代码仅供参考,具体实现需要根据项目需求进行调整。