Android 探索Bottom sheets的使用

在Android Support Library 23.2版本推出之後，我們可以看到一些新的特性,例如AppCompat DayNight主題，BottomSheet等，其中BottomSheet控件用於從屏幕底部向上滑動，以顯示更多的內容。本篇文章是想總結一下我在學習BottomSheet過程中的一些筆記以及一些需要注意的地方。

首先我們來看一下效果圖

這個效果的實現很簡單，甚至基本不需要java代碼,我們只需要給這個可滑動的view添加BottomSheetBehavior 表現行為即可，把這個behaviZ喎?/kf/ware/vc/" target="_blank" class="keylink">vcta4tqjOqmFuZHJvaWQuc3VwcG9ydC5kZXNpZ24ud2lkZ2V0LkJvdHRvbVNoZWV0QmVoYXZpb3K+zb/J0tS077W91eLW1tCnufvBy6OswLS/tL+0tPrC67DJPC9wPg0KPHByZSBjbGFzcz0="brush:java;">

看到LinearLayout的behavior了吧，在這裡我們添加BottomSheetBehavior表現行為而已，其他的地方沒有任何特殊的。LinearLayout裡面的布局，至於定義成什麼樣就看你自己想怎麼寫啦。
雖說我們可以不需要任何java代碼就可以實現，不過這裡我們還是希望可以通過按鈕去控制它的一個顯示情況：

 public void fab(View view) {
        BottomSheetBehavior behavior = BottomSheetBehavior.from(findViewById(R.id.layout));
        if (behavior.getState() == BottomSheetBehavior.STATE_EXPANDED) {
            behavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
        } else {
            behavior.setState(BottomSheetBehavior.STATE_EXPANDED);
        }
    }

代碼也很簡單，首先我們通過BottomSheetBehavior.from()方法來獲取到它的Behavior，然後通過getState方法來判斷現在的狀態，如果是展開的狀態，我們就讓它收縮起來；反之，則展開。
其中BottomSheet 有這麼幾種狀態：

STATE_COLLAPSED ：被折疊的狀態 STATE_SETTING ：沉降，我的理解是視圖從脫離手指自由滑動到最終停下的這一小段時間 STATE_EXPANDED ：完全展開的狀態 STATE_HIDDEN ：被隱藏的狀態，默認是false，可通過app:behavior_hideable屬性設置 STATE_DRAGGING ：被拖拽的狀態

Support Library 23.2中還提供了BottomSheetDialog和BottomSheetDialogFragment。BottomSheetDialog的用法與普通的dialog差不多，顯示的內容可以是列表，也可以是簡單的對話，當顯示的內容一滑入屏幕時，屏幕的其余部分會變暗，以襯托Dialog重點。下面看下BottomSheetDialog的簡單使用：

 BottomSheetDialog dialog = new BottomSheetDialog(this);
        dialog.setContentView(R.layout.dialog_layout);
        dialog.show();

下面我們使用BottomSheetDialog結合RecyclerView來顯示一個含有一個列表的dialog，效果圖如下：

使用BottomSheetDialog的話，當我們點擊按鈕顯示的時候，它只會先出現一部分，我們拖動它的時候，它會占滿屏幕，現在我們就來看一下代碼

package per.lijuan.bottomsheetdome;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomSheetBehavior;
import android.support.design.widget.BottomSheetDialog;
import android.support.v4.view.ViewCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    public BottomSheetBehavior behavior;
    public RecyclerView recyclerView;
    public MyAdapter adapter;
    private BottomSheetDialog dialog;

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

    private void initView() {
        recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));

        adapter = new MyAdapter();
        adapter.setItemClickListener(new onItemClickListener(2));
        recyclerView.setAdapter(adapter);
        recyclerView.setVisibility(View.GONE);

        behavior = BottomSheetBehavior.from(recyclerView);
        behavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
                if (newState == BottomSheetBehavior.STATE_COLLAPSED || newState == BottomSheetBehavior.STATE_HIDDEN) {
                    recyclerView.setVisibility(View.GONE);
                }
            }

            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffset) {
                recyclerView.setVisibility(View.VISIBLE);
                ViewCompat.setAlpha(recyclerView, slideOffset);
            }
        });
    }

    public void fab(View view) {
        BottomSheetBehavior behavior = BottomSheetBehavior.from(findViewById(R.id.layout));
        if (behavior.getState() == BottomSheetBehavior.STATE_EXPANDED) {
            behavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
        } else {
            behavior.setState(BottomSheetBehavior.STATE_EXPANDED);
        }
    }

    public void onClick1(View view) {
        if (behavior.getState() == behavior.STATE_EXPANDED) {
            behavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
        } else {
            behavior.setState(BottomSheetBehavior.STATE_EXPANDED);
        }
    }

    public void onClick2(View view) {
        RecyclerView recyclerView = (RecyclerView) LayoutInflater.from(this)
                .inflate(R.layout.list, null);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
        MyAdapter adapter = new MyAdapter();
        recyclerView.setAdapter(adapter);

        dialog = new BottomSheetDialog(this);
        dialog.setContentView(recyclerView);
        dialog.show();
        adapter.setItemClickListener(new onItemClickListener(3));
    }

    public class onItemClickListener implements MyAdapter.ItemClickListener {
        private int index;

        public onItemClickListener(int index) {
            this.index = index;
        }

        @Override
        public void onItemClick(int position) {
            Toast.makeText(MainActivity.this, "您點擊了item" + position, Toast.LENGTH_LONG).show();
            if (index == 2) {
                behavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
            } else if (index == 3) {
                dialog.dismiss();
            }
        }
    }
}

MyAdapter.class

package per.lijuan.bottomsheetdome;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * 適配器
 * Created by lijuan on 2016/9/7.
 */
public class MyAdapter extends RecyclerView.Adapter {

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

    @Override
    public void onBindViewHolder(final ViewHolder holder, final int position) {
        holder.mTextView.setText("item");
        holder.mTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mItemClickListener.onItemClick(position);
            }
        });
    }

    @Override
    public int getItemCount() {
        return 8;
    }

    class ViewHolder extends RecyclerView.ViewHolder {

        public TextView mTextView;

        public ViewHolder(View view) {
            super(view);
            mTextView = (TextView) view.findViewById(R.id.textview);
        }
    }

    public interface ItemClickListener {
        void onItemClick(int position);
    }

    public ItemClickListener mItemClickListener;

    public void setItemClickListener(ItemClickListener listener) {
        mItemClickListener = listener;
    }
}

list.xml

list_item.xml

好了，本篇文章就這樣子啦，存在總結不到位的地方還望指導，感謝^_^