custom_dialog.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_margin="@dimen/space_8">

    <TextView
        android:id="@+id/textView"
        style="@style/big_title.black"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:padding="@dimen/space_8"
        android:text="@string/label_report"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/edt_comment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"        
        android:hint="@string/label_type_your_comment"
        android:inputType="textMultiLine|text"
        android:padding="@dimen/space_8"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <Button
        android:id="@+id/buttonSubmit"        
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/label_submit"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/edt_comment" />

    <Button
        android:id="@+id/buttonCancel"        
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="@string/label_cancel"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/edt_comment" />


</android.support.constraint.ConstraintLayout>

CustomDialog.java

final AlertDialog dialogBuilder = new AlertDialog.Builder(this).create();
        LayoutInflater inflater = this.getLayoutInflater();
        View dialogView = inflater.inflate(R.layout.custom_dialog, null);

        final EditText editText = (EditText) dialogView.findViewById(R.id.edt_comment);
        Button button1 = (Button) dialogView.findViewById(R.id.buttonSubmit);
        Button button2 = (Button) dialogView.findViewById(R.id.buttonCancel);

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                dialogBuilder.dismiss();
            }
        });
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // DO SOMETHINGS
                dialogBuilder.dismiss();
            }
        });

        dialogBuilder.setView(dialogView);
        dialogBuilder.show();

Great Thanks.