底部动作条

底部动作条(Bottom Sheets)是一个从屏幕底部边缘向上滑出的一个面板，使用这种方式向用户呈现一组功能。底部动作条呈现了简单、清晰、无需额外解释的一组操作。

使用环境

底部动作条(Bottom Sheets)特别适合有三个或者三个以上的操作需要提供给用户选择、并且不需要对操作有额外解释的情景。如果只有两个或者更少的操作，或者需要详加描述的，可以考虑使用菜单(Menu)或者对话框替代。

底部动作条(Bottom Sheets)可以是列表样式的也可以是宫格样式的。宫格布局可以增加视觉的清晰度。

你可以使用底部动作条(Bottom Sheets)展示和其 app 相关的操作，比如做为进入其他 app 的入口(通过 app 的 icon 进入)。

行为

显示底部动作条的时候，动画应该从屏幕底部边缘向上展开。根据上一步的内容，向用户展示用户上一步的操作之后能够继续操作的内容，并提供模态[1]的选择。点击其他区域会使得底部动作条伴随下滑的动画关闭掉。如果这个窗口包含的操作超出了默认的显示区域，这个窗口需要可以滑动。滑动操作应当向上拉起这个动作条的内容，甚至可以覆盖整个屏幕。当窗口覆盖整个屏幕的时候，需要在上部的标题栏左侧增加一个收起按钮。

添加依赖：

compile 'com.android.support:design:24.2.0'

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:onClick="click"
        android:text="BottomSheet" />

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_behavior="@string/bottom_sheet_behavior">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:gravity="center"
            android:orientation="vertical">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:minHeight="50dp"
                android:gravity="center_vertical"
                android:drawableLeft="@mipmap/ic_launcher"
                android:text="BottomSheet布局" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:minHeight="50dp"
                android:drawableLeft="@mipmap/ic_launcher"
                android:text="BottomSheet布局" />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:minHeight="50dp"
                android:drawableLeft="@mipmap/ic_launcher"
                android:text="BottomSheet布局" />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:minHeight="50dp"
                android:drawableLeft="@mipmap/ic_launcher"
                android:text="BottomSheet布局" />
        </LinearLayout>

    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>

public class MainActivity extends AppCompatActivity {

    private BottomSheetBehavior<View> bottomSheet;

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

        init();
    }

    private void init() {
        bottomSheet.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
                //newState 有四个状态 ：
                //展开 BottomSheetBehavior.STATE_EXPANDED
                //收起 BottomSheetBehavior.STATE_COLLAPSED
                //拖动 BottomSheetBehavior.STATE_DRAGGING
                //下滑 BottomSheetBehavior.STATE_SETTLING
            }

            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffset) {
            //这里是拖拽中的回调，slideOffset为0-1 完全收起为0 完全展开为1
            }
        });
    }
}

BottomSheetDialog

public class BottomSheetDialogActivity extends AppCompatActivity{
    private List<String> mList;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bottomsheet);
        initData();
    }

    private void initData() {
        mList = new ArrayList<>();
        for(int i=0; i<20; i++){
            mList.add("item "+i);
        }
    }

    public void click1(View view){
        final BottomSheetDialog bottomSheetDialog = new BottomSheetDialog(this);
        //创建recyclerView
        RecyclerView recyclerView = new RecyclerView(this);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);
        RecyclerAdapter recyclerAdapter = new RecyclerAdapter(mList,this);
        recyclerView.setAdapter(recyclerAdapter);
        recyclerAdapter.setOnItemClickListener(new RecyclerAdapter.OnItemClickListener() {
            @Override
            public void onItemClickListener(View item, int position) {
                Toast.makeText(BottomSheetDialogActivity.this, "item "+position, Toast.LENGTH_SHORT).show();
                bottomSheetDialog.dismiss();
            }
        });

        bottomSheetDialog.setContentView(recyclerView);
        bottomSheetDialog.show();
    }
}

public class RecyclerAdapter  extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder>{

    private List<String> list;
    private Context mContext;
    private OnItemClickListener onItemClickListener;

    public RecyclerAdapter(List<String> list, Context mContext) {
        this.list = list;
        this.mContext = mContext;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View inflate = LayoutInflater.from(mContext).inflate(R.layout.item_layou, parent, false);
        return new ViewHolder(inflate);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, final int position) {
        holder.tv.setText(list.get(position));
        holder.tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(onItemClickListener!=null){
                    onItemClickListener.onItemClickListener(v,position);
                }
            }
        });
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder{
        TextView tv;
        public ViewHolder(View itemView) {
            super(itemView);
            tv = (TextView) itemView.findViewById(R.id.item_tv);
        }
    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    public interface OnItemClickListener{
        void onItemClickListener(View item, int position);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:orientation="vertical">

    <TextView
        android:id="@+id/item_tv"
        android:layout_width="match_parent"
        android:layout_height="50dp" />
</LinearLayout>