FloatingActionButton在用户向下滚动或添加新视图时向下滚动

Question

我目前正在开设一个大学应用，其中1个UI线程负责添加学期按钮。当应用程序旋转并单击FloatingActionButton以添加视图时，在视图位于屏幕下方后，按钮会在每次单击时向下滚动按钮。我试图调整我的XML但不幸的是没有发生任何事情。我的问题是当用户上下滚动时，如何在屏幕上的同一位置保持我的FAB？

这是我的UI线程：

public class MainActivity extends AppCompatActivity {

    int counter = 0;

    FloatingActionButton addingSemester;
    Button semesterButton;
    LinearLayout semesterLayout;
    RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
            AppBarLayout.LayoutParams.MATCH_PARENT,
            AppBarLayout.LayoutParams.WRAP_CONTENT);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        addingSemester = (FloatingActionButton) findViewById(R.id.addActionButton);
        semesterLayout = (LinearLayout) findViewById(R.id.main_layout);
        semesterButton = new Button(MainActivity.this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.delete) {
            new AlertDialog.Builder(MainActivity.this)
            .setTitle("Delete entry")
                    .setMessage("Are you sure you want to delete everything?")
                    .setCancelable(true)
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            semesterLayout.removeAllViews();
                            counter = 0;
                        }
                    })
                    .setNegativeButton("No", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.cancel();
                        }
                    })
                    .show();
            return true;
        }

        return super.onOptionsItemSelected(item);

    }

    public void onFloatActionButtonClick(View view) {
        semesterButton = new Button(MainActivity.this);
        if (counter < 8) {
            semesterButton.setId(counter + 1);
            semesterButton.setText("Semester " + (counter + 1));
            semesterButton.setBackgroundColor(getColor(R.color.colorPrimary));
            semesterButton.setTextColor(Color.WHITE);
            lp.setMargins(24, 24, 24, 24);
            semesterButton.setLayoutParams(lp);
            semesterLayout.addView(semesterButton);
            counter++;
            semesterButton.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    final Button b = (Button) v;
                    b.setTag(b.getText().toString());
                    b.setBackgroundColor(Color.RED);
                    b.setText("Delete");

                    new AlertDialog.Builder(MainActivity.this)
                            .setTitle("Delete entry")
                            .setMessage("Are you sure you want to delete this entry?")
                            .setCancelable(true)
                            .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog, int which) {
                                    semesterLayout.removeView(b);
                                    counter--;
                                    for (int i = 0; i < semesterLayout.getChildCount(); i++) {
                                        ((Button) semesterLayout.getChildAt(i)).setText("Semester " + (i + 1));
                                    }
                                }
                            })
                            .setNegativeButton("No", new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog, int which) {
                                    b.cancelLongPress();
                                    b.setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
                                    b.setText(b.getTag().toString());
                                    dialog.cancel();

                                }
                            })
                            .show();
                    return true;
                }
            });

        } else if (counter == 8) {
            Toast.makeText(MainActivity.this, "You cannot add more than 8 semesters", Toast.LENGTH_SHORT).show();
        }
    }
}

这是我的XML

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout
    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="wrap_content"
    android:background="#FFFFFF"
    tools:context="myapp.onur.journeygpacalculator.MainActivity">

    <ScrollView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true"
        >
        <LinearLayout
            android:id="@+id/main_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:padding="6dp">
        </LinearLayout>
    </ScrollView>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/addActionButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_margin="16dp"
        android:clickable="true"
        android:longClickable="true"
        android:onClick="onFloatActionButtonClick"
        android:src="@drawable/ic_add_black_48dp"
        android:tint="@color/colorWhite"
        app:backgroundTint="@color/colorPrimary"
        app:layout_behavior="com.myapp.onur.journeygpacalculator.ScrollingFABBehavior"
        android:elevation="6dp"
        app:borderWidth="0dp"/>
</RelativeLayout>