Bottom Sheet does not EXPANDED or COLLAPSED

问题

I have created very simple Bottom Sheet at my tested project flowing this page .First i created my layout :

<?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"
    android:id="@+id/mainContent"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:paddingTop="24dp">

            <Button
                android:id="@+id/btn_1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Button 1"
                android:padding="16dp"
                android:layout_margin="8dp"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_green_dark"/>
        </LinearLayout>

    </ScrollView>

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="350dp"
        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="Bottom Sheets"
            android:paddingTop="16dp"
            android:textSize="16sp"/>

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

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

In MainActivity i've written these codes:

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private BottomSheetBehavior mBottomSheetBehavior;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        View bottomSheet = findViewById(R.id.bottom_sheet);

        Button btn1 = findViewById(R.id.btn_1);
        btn1.setOnClickListener(this);

        mBottomSheetBehavior = BottomSheetBehavior.from(bottomSheet);
        mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);

    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn_1:
                mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
                break;
        }
    }
}

But when i run app on emulator BottomSheetBehavior is EXPANDED!!!When i changed my code to this:

switch (view.getId()) {
    case R.id.btn_1:
        mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
        break;

And press btn_1 BottomSheetBehavior does not collapsed? What is the problem? This is my gradle:

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:28.0.0-alpha3'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    implementation 'com.android.support:design:28.0.0-alpha3'
}

回答1:

You have to Add this two lines in your bottom sheet layout file

app:behavior_peekHeight="0dp"
app:layout_behavior="android.support.design.widget.BottomSheetBehavior"

layout_behavior - to apply the bottom sheet collapse and expand behavior to up and down the layout peekHeight - the height of layout you want to show initial when an activity launch , you can change it according to view height

if this is already added then can you please share your main activity xml file where you have include the bottom sheet layout

来源：https://stackoverflow.com/questions/51017935/bottom-sheet-does-not-expanded-or-collapsed