Android Bottom Sheet

Google introduced material design was a revolution in the Android design which was announced during the 2014 Google I/O conference. To maintain the official trend, Google brought the Design support library on the 2015 Google I/O conference. This design library has a set of material design based UI components & it's continuously improving. Meanwhile, in the 23.2 release of the library there is a new component was added namely Bottom-Sheet. Bottom sheet is an UI component that slides up from bottom of the screen to bring more content.

This article describes how to implement a bottom sheet in the Android projects.

Step - 1: Add the dependencies in the application's gradle file:

dependencies {
    compile 'com.android.support:appcompat-v7:25.1.1'
    compile 'com.android.support:design:25.1.0'
}

Step - 2: Create the XML layout file (activity_main.xml):

<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"
    android:fitsSystemWindows="true">
 
     <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Show Bottom Sheet"
        android:padding="16dp"
        android:layout_margin="8dp"
        android:textColor="@android:color/white"
        android:background="@android:color/holo_green_dark"/>
    
    <android.support.v4.widget.NestedScrollView
        android:id="@+id/bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:clipToPadding="true"
        android:background="@android:color/holo_orange_light"
        app:layout_behavior="android.support.design.widget.BottomSheetBehavior">
 
        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Hello! I am a bottom sheet."
            android:padding="16dp"
            android:textSize="16sp"/>
 
    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>

You must need to use a CoordinatorLayout container for the views to get the bottom sheet component. In the bottom of the XML file, you can see that there is a NestedScrollView containing a TextView. While any container view can be used in a bottom sheet, scrolling can only properly occur if you use a container that supports nested scrolling, such as the NestedScrollView or a RecyclerView.

For a container to be recognized by the Design support library as a bottom sheet container, you need to include the layout_behavior attribute with a value of android.support.design.widget.BottomSheetBehavior.

Step - 3: Write Java functionality (MainActivity.java):

public class MainActivity extends AppCompatActivity implements OnClickListener {
  private BottomSheetBehavior mBottomSheetBehavior;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    setContentView(R.layout.activity_user);
    
    View bottomSheet = findViewById( R.id.bottom_sheet );
    Button button = (Button) findViewById( R.id.button );
    button.setOnClickListener(this);
    mBottomSheetBehavior = BottomSheetBehavior.from(bottomSheet);
    mBottomSheetBehavior.setPeekHeight(0);  // 0 if you don't want to show the bottom sheet on the starting activity.
  }
  
  public void onClick(View v) {
      switch (v.getId()) {
                case R.id.button:
                   mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
                  break;
    }
}

There are 03 states on the BottomSheetBehavior and you can handle these states via the setState(...) method:

1. STATE_EXPANDED: To fully expand the bottom sheet.
2. STATE_HIDE: To fully hide the bottom sheet.
3. STATE_COLLAPSED: To set the bottom sheet height with the value set on the peekHeight attribute.

That's all about a basic bottom sheet. Now, while the button is clicked, then a bottom sheet will be seen from the bottom edge.

References:

• http://www.hidroh.com/2016/06/17/bottom-sheet-everything/?utm_source=androiddevdigest
• https://material.io/guidelines/components/bottom-sheets.html