Effect in gallery with android studio

Well folks I'm having a problem that I'm not finding the answer, how can I create a gallery with this effect: CurrentlyIonlyhavethestructureoftheappready,I'mstartingtoencodetheeffectsbutIpackeditinthejavaphotogalleryofactivitycurrent:

protectedvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.selecionar_fotos);DisplayMetricsdm=newDisplayMetrics();getWindowManager().getDefaultDisplay().getMetrics(dm);intwidth=dm.widthPixels;intheight=dm.heightPixels;getWindow().setLayout(width,height);botao=findViewById(R.id.btn_fechar_escolher_molduras);botao.setOnClickListener(newView.OnClickListener(){@OverridepublicvoidonClick(Viewv){finish();//Finalizaessaactivityevoltaparaanterior}});

mainactivitycode:

protectedvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);ToolbarmToolbar=(Toolbar)findViewById(R.id.toolbar);setSupportActionBar(mToolbar);Buttonbtn=(Button)findViewById(R.id.btn_mandar_foto);btn.setOnClickListener(newView.OnClickListener(){@OverridepublicvoidonClick(Viewview){startActivity(newIntent(MainActivity.this,Pop.class));}});}

XMLcode:

<LinearLayoutandroid:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:orientation="horizontal">

                <Button
                    android:id="@+id/btn_seta_esq"
                    android:layout_width="80dp"
                    android:layout_height="50dp"
                    android:layout_gravity="center"
                    android:layout_marginLeft="10dp"
                    android:layout_weight="1"
                    android:background="@drawable/btn_seta_esq"
                    android:clickable="true"
                    />

                <FrameLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_marginTop="10dp"
                    android:layout_weight="1">

                    <LinearLayout
                        android:layout_width="160dp"
                        android:layout_height="240dp"
                        android:layout_marginLeft="90dp"
                        android:background="@color/ic_launcher_background"
                        android:orientation="horizontal"></LinearLayout>

                    <LinearLayout
                        android:layout_width="160dp"
                        android:layout_height="240dp"
                        android:layout_marginLeft="55dp"
                        android:layout_marginTop="15dp"
                        android:background="@color/colorPrimary"
                        android:orientation="horizontal"></LinearLayout>

                    <LinearLayout
                        android:layout_width="160dp"
                        android:layout_height="240dp"
                        android:layout_marginLeft="20dp"
                        android:layout_marginTop="35dp"
                        android:background="@color/colorAccent"
                        android:orientation="horizontal">
                    </LinearLayout>

                </FrameLayout>

                <Button
                    android:id="@+id/btn_seta_dir"
                    android:layout_width="80dp"
                    android:layout_height="50dp"
                    android:layout_gravity="center"
                    android:layout_marginRight="10dp"
                    android:layout_weight="1"
                    android:background="@drawable/btn_seta_dir"
                    android:clickable="true"
                    />

            </LinearLayout>