Dragging panel with ViewDragHelper

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white">

    <Button
        android:id="@+id/hidden_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hidden button"
        android:textSize="64sp" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Some text"
        android:layout_below="@id/hidden_button"
        android:padding="10dp"
        android:textSize="20sp"/>

    <com.whiterabbit.dragqueen.DraggingPanel
        android:id="@+id/outer_layout"
        android:layout_width="match_parent"
        android:layout_height="350dp"
        android:layout_alignParentBottom="true">

        <LinearLayout
            android:id="@+id/main_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:clickable="true"
            android:background="#1E90FF"
            android:orientation="vertical">

            <LinearLayout
                android:id="@+id/queen_button"
                android:layout_width="match_parent"
                android:layout_height="50dp"
                android:layout_marginTop="10dp"
                android:orientation="horizontal"
                android:weightSum="3">

                <EditText
                    android:id="@+id/resolverComentar"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="5dp"
                    android:layout_weight="2.5"
                    android:ems="10"
                    android:inputType="textMultiLine"
                    android:padding="10dp"
                    android:scrollbars="vertical" />

                <Button
                    android:id="@+id/sendMessage"
                    android:layout_width="50dp"
                    android:layout_height="50dp"
                    android:layout_gravity="center"
                    android:layout_marginEnd="5dp"
                    android:layout_weight="0.5"
                    android:background="@android:drawable/ic_menu_send"
                    android:enabled="false"
                    android:textSize="16sp"
                    android:textStyle="bold" />
            </LinearLayout>

            <LinearLayout
                android:id="@+id/buttonsLayout"
                android:layout_width="match_parent"
                android:layout_height="60dp"
                android:background="?android:colorBackground"
                android:orientation="horizontal"
                android:weightSum="2">

                <Button
                    android:id="@+id/button1"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout_margin="5dp"
                    android:layout_weight="1"
                    android:gravity="center"
                    android:background="#ADFF2F"
                    android:text="Accept"
                    android:textAllCaps="false"
                    android:textSize="20sp" />

                <Button
                    android:id="@+id/button2"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout_margin="5dp"
                    android:layout_weight="1"
                    android:gravity="center"
                    android:padding="10dp"
                    android:text="Decline"
                    android:background="#FF4500"
                    android:textAllCaps="false"
                    android:textSize="20sp" />
            </LinearLayout>

            <WebView
                android:id="@+id/webview"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </LinearLayout>
    </com.whiterabbit.dragqueen.DraggingPanel>
</RelativeLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.whiterabbit.dragqueen" >

    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:windowSoftInputMode="adjustPan">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

DraggingPanel.java

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

public class DraggingPanel extends RelativeLayout {
    private final double AUTO_OPEN_SPEED_LIMIT = 800.0;
    private int mDraggingState = 0;
    private LinearLayout mQueenButton;
    private ViewDragHelper mDragHelper;
    private int mDraggingBorder;
    private int mVerticalRange;
    private boolean mIsOpen;


    public class DragHelperCallback extends ViewDragHelper.Callback {
        @Override
        public void onViewDragStateChanged(int state) {
            if (state == mDraggingState) { // no change
                return;
            }
            if ((mDraggingState == ViewDragHelper.STATE_DRAGGING || mDraggingState == ViewDragHelper.STATE_SETTLING) &&
                 state == ViewDragHelper.STATE_IDLE) {
                // the view stopped from moving.

                if (mDraggingBorder == 0) {
                    onStopDraggingToClosed();
                } else if (mDraggingBorder == mVerticalRange) {
                    mIsOpen = true;
                }
            }
            if (state == ViewDragHelper.STATE_DRAGGING) {
                onStartDragging();
            }
            mDraggingState = state;
        }

        @Override
        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
            mDraggingBorder = top;
        }

        public int getViewVerticalDragRange(View child) {
            return mVerticalRange;
        }

        @Override
        public boolean tryCaptureView(View view, int i) {
            return (view.getId() == R.id.main_layout);
        }

        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            final int topBound = getPaddingTop();
            final int bottomBound = mVerticalRange;
            return Math.min(Math.max(top, topBound), bottomBound);
        }

        @Override
        public void onViewReleased(View releasedChild, float xvel, float yvel) {
            final float rangeToCheck = mVerticalRange;
            if (mDraggingBorder == 0) {
                mIsOpen = false;
                return;
            }
            if (mDraggingBorder == rangeToCheck) {
                mIsOpen = true;
                return;
            }
            boolean settleToOpen = false;
            if (yvel > AUTO_OPEN_SPEED_LIMIT) { // speed has priority over position
                settleToOpen = true;
            } else if (yvel < -AUTO_OPEN_SPEED_LIMIT) {
                settleToOpen = false;
            } else if (mDraggingBorder > rangeToCheck / 2) {
                settleToOpen = true;
            } else if (mDraggingBorder < rangeToCheck / 2) {
                settleToOpen = false;
            }

            final int settleDestY = settleToOpen ? mVerticalRange : 0;

            if(mDragHelper.settleCapturedViewAt(0, settleDestY)) {
                ViewCompat.postInvalidateOnAnimation(DraggingPanel.this);
            }
        }
    }

    public DraggingPanel(Context context, AttributeSet attrs) {
        super(context, attrs);
        mIsOpen = false;
    }

    @Override
    protected void onFinishInflate() {
        mQueenButton  = findViewById(R.id.queen_button);
        mDragHelper = ViewDragHelper.create(this, 1.0f, new DragHelperCallback());
        mIsOpen = false;
        super.onFinishInflate();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        mVerticalRange = (int) (h * 0.84);
        super.onSizeChanged(w, h, oldw, oldh);
    }

    private void onStopDraggingToClosed() {
        // To be implemented
    }

    private void onStartDragging() {

    }

    private boolean isQueenTarget(MotionEvent event) {
        int[] queenLocation = new int[2];
        mQueenButton.getLocationOnScreen(queenLocation);
        int upperLimit = queenLocation[1] + mQueenButton.getMeasuredHeight();
        int lowerLimit = queenLocation[1];
        int y = (int) event.getRawY();
        return (y > lowerLimit && y < upperLimit);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (isQueenTarget(event) && mDragHelper.shouldInterceptTouchEvent(event)) {
                return true;
        } else {
            return false;
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (isQueenTarget(event) || isMoving()) {
            mDragHelper.processTouchEvent(event);
            return true;
        } else {
            return super.onTouchEvent(event);
        }
    }

    @Override
    public void computeScroll() { // needed for automatic settling.
        if (mDragHelper.continueSettling(true)) {
            ViewCompat.postInvalidateOnAnimation(this);
        }
    }

    public boolean isMoving() {
        return (mDraggingState == ViewDragHelper.STATE_DRAGGING ||
                mDraggingState == ViewDragHelper.STATE_SETTLING);
    }

    public boolean isOpen() {
        return mIsOpen;
    }
}

MainActivity.java

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;


public class MainActivity extends Activity implements View.OnClickListener {
    private LinearLayout mQueen;
    private Button mHidden, accept, decline;
    private OuterLayout mOuterLayout;
    private LinearLayout mMainLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mOuterLayout = findViewById(R.id.outer_layout);
        mMainLayout = findViewById(R.id.main_layout);
        mHidden = findViewById(R.id.hidden_button);
        accept = findViewById(R.id.button1);
        accept.setOnClickListener(this);
        decline = findViewById(R.id.button2);
        decline.setOnClickListener(this);
        mHidden.setOnClickListener(this);
        mQueen = findViewById(R.id.queen_button);
        mQueen.setOnClickListener(this);
        mMainLayout.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
            @Override
            public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
                if (mOuterLayout.isMoving()) {
                    v.setTop(oldTop);
                    v.setBottom(oldBottom);
                    v.setLeft(oldLeft);
                    v.setRight(oldRight);
                }
            }
        });
    }

    @Override
    public void onClick(View v) {
        Button b = (Button) v;
        Toast t = Toast.makeText(this, b.getText() + " clicked", Toast.LENGTH_SHORT);
        t.show();
    }
}