底部弹窗BottomSheetBehavior

//引用依赖

compile 'com.android.support:design:27.1.1'
//代码

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final BottomSheetBehavior bottomSheetBehavior=BottomSheetBehavior.from(findViewById(R.id.design_bottom_sheet1));
        //设置默认先隐藏
        bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //根据状态不同显示隐藏
                if (bottomSheetBehavior.getState() == BottomSheetBehavior.STATE_HIDDEN) {
                    bottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
                } else if (bottomSheetBehavior.getState() == BottomSheetBehavior.STATE_COLLAPSED) {
                    bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
                }
            }
        });
        //设置监听事件
        bottomSheetBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
                //拖动
            }

            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffset) {
                //状态变化
            }
        });
    }
}
//布局

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:orientation="vertical"
        android:layout_height="match_parent">
        //按钮要使用布局包裹否则会浮在BottomSheetBehavior之上
        <Button
            android:layout_width="wrap_content"
            android:text="打开"
            android:id="@+id/bt"
            android:layout_height="wrap_content" />
    </LinearLayout>
    <LinearLayout
        android:id="@+id/design_bottom_sheet1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" //这个高度决定了BottomSheetBehavior的总高度
        android:background="@color/colorAccent"
        app:behavior_hideable="true" //可以隐藏
        app:behavior_peekHeight="300dp" //设置弹出时的高度
        android:orientation="vertical"
        app:elevation="6dp"
        app:layout_behavior="@string/bottom_sheet_behavior" //这一句固定要加>
        <ImageView
            android:layout_width="wrap_content"
            android:layout_gravity="center"
            android:src="@mipmap/ic_launcher"
            android:layout_marginTop="20dp"
            android:layout_height="wrap_content" />
    </LinearLayout>
</android.support.design.widget.CoordinatorLayout>