android使用BottomShee+RecycleView 实现抖音评论收起

要实现抖音评论收起功能，可以使用以下步骤：

1. 在布局文件中添加BottomSheet和RecycleView。

2. 创建一个Adapter类来处理RecycleView的数据和布局。

3. 在Adapter中，添加一个方法用于控制评论的展开和收起。

4. 在Activity中，将Adapter设置给RecycleView，并在点击收起按钮时调用Adapter中的方法。

5. 在BottomSheet的回调函数中，设置BottomSheet的高度为RecycleView的高度。

以下是示例代码：

1. 布局文件

<androidx.coordinatorlayout.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- 底部弹出的BottomSheet -->
    <com.google.android.material.bottomsheet.BottomSheetBehavior
        android:id="@+id/bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:behavior_hideable="true"
        app:behavior_peekHeight="0dp"
        app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </com.google.android.material.bottomsheet.BottomSheetBehavior>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

2. Adapter类

public class CommentAdapter extends RecyclerView.Adapter<CommentAdapter.CommentViewHolder> {

    private List<Comment> commentList;
    private boolean isExpanded = false;

    public CommentAdapter(List<Comment> commentList) {
        this.commentList = commentList;
    }

    @NonNull
    @Override
    public CommentViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_comment, parent, false);
        return new CommentViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull CommentViewHolder holder, int position) {
        Comment comment = commentList.get(position);
        holder.tvComment.setText(comment.getCommentText());
    }

    @Override
    public int getItemCount() {
        if (isExpanded) {
            return commentList.size();
        } else {
            return Math.min(commentList.size(), 2); // 只显示前两条评论
        }
    }

    public void expandComments() {
        isExpanded = true;
        notifyDataSetChanged();
    }

    static class CommentViewHolder extends RecyclerView.ViewHolder {

        TextView tvComment;

        CommentViewHolder(View itemView) {
            super(itemView);
            tvComment = itemView.findViewById(R.id.tv_comment);
        }
    }
}

3. Activity代码

public class MainActivity extends AppCompatActivity {

    private CommentAdapter commentAdapter;
    private BottomSheetBehavior bottomSheetBehavior;

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

        RecyclerView recyclerView = findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        List<Comment> commentList = generateDummyComments();
        commentAdapter = new CommentAdapter(commentList);
        recyclerView.setAdapter(commentAdapter);

        Button btnCollapse = findViewById(R.id.btn_collapse);
        btnCollapse.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                commentAdapter.expandComments();
            }
        });

        // 获取BottomSheetBehavior实例
        View bottomSheet = findViewById(R.id.bottom_sheet);
        bottomSheetBehavior = BottomSheetBehavior.from(bottomSheet);
        bottomSheetBehavior.setPeekHeight(0);
        bottomSheetBehavior.setHideable(true);
        bottomSheetBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
                if (newState == BottomSheetBehavior.STATE_HIDDEN) {
                    finish();
                }
            }

            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffset) {
                // 设置BottomSheet的高度为RecycleView的高度
                View recyclerView = bottomSheet.findViewById(R.id.recyclerView);
                ViewGroup.LayoutParams layoutParams = bottomSheet.getLayoutParams();
                layoutParams.height = (int) (recyclerView.getHeight() * (1 - slideOffset));
                bottomSheet.setLayoutParams(layoutParams);
            }
        });
    }

    private List<Comment> generateDummyComments() {
        List<Comment> commentList = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            Comment comment = new Comment("这是第" + (i + 1) + "条评论");
            commentList.add(comment);
        }
        return commentList;
    }
}

这样就可以实现抖音评论收起功能了。当点击收起按钮时，RecycleView会展开显示所有评论；当底部弹出的BottomSheet向上滑动时，会动态改变BottomSheet的高度，实现平滑的动画效果。