Android Gallery Crash

[BDany]

Salve a tutti, stavo facendo una piccola app su android studio e mentre provavo a fare una gallery, solo che quando la provo l'app mi va in crash, vi posto il codice, se qualcuno ha voglia e tempo di dargli un occhiata e dirmi dove sbaglio, sarebbe molto gentile! Grazie a tutti!

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#225ED6">


    <ImageView
        android:id="@+id/selected"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_above="@+id/gallery_relative_layout"
        android:layout_marginLeft="30dip"
        android:layout_marginRight="30dip"
        android:layout_marginTop="30dip" />


    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:layout_above="@+id/gallery_relative_layout"
        android:layout_marginTop="300dp"
        android:background="#000000" />


    <RelativeLayout
        android:id="@+id/gallery_relative_layout"
        android:layout_width="fill_parent"
        android:layout_height="200dip"
        android:layout_alignParentBottom="true"
        android:orientation="horizontal"
        android:paddingTop="20dp" >


        <HorizontalScrollView
            android:id="@+id/hor_scroll_view"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >


            <LinearLayout
                android:id="@+id/gallery"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="horizontal" >


                <ImageView
                    android:id="@+id/pdma"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdma" />


                <ImageView
                    android:id="@+id/pdmb"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdmb" />


                <ImageView
                    android:id="@+id/pdmc"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdmc" />


                <ImageView
                    android:id="@+id/pdmd"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdmd" />


                <ImageView
                    android:id="@+id/pdmf"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdmf" />


                <ImageView
                    android:id="@+id/pdmg"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:onClick="biggerView"
                    android:src="@drawable/pdmg" />




            </LinearLayout>
        </HorizontalScrollView>
    </RelativeLayout>




</RelativeLayout>

JAVA

    ImageView im;






    public void biggerView(View v)
    {
        im=(ImageView)findViewById(R.id.selected);


        switch (v.getId())
        {
            case R.id.pdma: im.setImageResource(R.drawable.pdma);
                break;
            case R.id.pdmb: im.setImageResource(R.drawable.pdmb);
                break;
            case R.id.pdmc: im.setImageResource(R.drawable.pdmc);
                break;
            case R.id.pdmd: im.setImageResource(R.drawable.pdmd);
                break;
            case R.id.pdmf: im.setImageResource(R.drawable.pdmf);
                break;
            case R.id.pdmg: im.setImageResource(R.drawable.pdmg);
                break;




        }
    }