Android实现炫酷背景图垂直循环滚动效果

public class AutoPollRecyclerView extends RecyclerView {    private static final long TIME_AUTO_POLL = 16;    AutoPollTask autoPollTask;    private boolean running; //标示是否正在自动轮询    private boolean canRun;//标示是否可以自动轮询,可在不需要的是否置false
    public AutoPollRecyclerView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        autoPollTask = new AutoPollTask(this);    }
    static class AutoPollTask implements Runnable {        private final WeakReference<AutoPollRecyclerView> mReference;
        //使用弱引用持有外部类引用->防止内存泄漏        public AutoPollTask(AutoPollRecyclerView reference) {            this.mReference = new WeakReference<AutoPollRecyclerView>(reference);        }
        @Override        public void run() {            AutoPollRecyclerView recyclerView = mReference.get();            if (recyclerView != null && recyclerView.running && recyclerView.canRun) {                recyclerView.scrollBy(2, 2);                recyclerView.postDelayed(recyclerView.autoPollTask, recyclerView.TIME_AUTO_POLL);            }        }    }
    //开启:如果正在运行,先停止->再开启    public void start() {        if (running)            stop();        canRun = true;        running = true;        postDelayed(autoPollTask, TIME_AUTO_POLL);    }
    public void stop() {        running = false;        removeCallbacks(autoPollTask);    }
    @Override    public boolean onTouchEvent(MotionEvent e) {        switch (e.getAction()) {            case MotionEvent.ACTION_DOWN:                if (running)                    stop();                break;            case MotionEvent.ACTION_UP:            case MotionEvent.ACTION_CANCEL:            case MotionEvent.ACTION_OUTSIDE:                if (canRun)                    start();                break;        }        //return  false，注释掉onTouchEvent()方法里面的stop和start方法，则列表自动滚动且不可触摸        return super.onTouchEvent(e);}}

public class AutoPollAdapter extends RecyclerView.Adapter<AutoPollAdapter.BaseViewHolder> {    private final Context mContext;

    public AutoPollAdapter(Context context) {        this.mContext = context;    }
    @Override    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View view = LayoutInflater.from(mContext).inflate(R.layout.auto_list_item, parent, false);        BaseViewHolder holder = new BaseViewHolder(view);        return holder;    }
    @Override    public void onBindViewHolder(BaseViewHolder holder, int position) {
    }
    @Override    public int getItemCount() {        return Integer.MAX_VALUE;    }
    class BaseViewHolder extends RecyclerView.ViewHolder {        ImageView imageView;
        public BaseViewHolder(View itemView) {            super(itemView);            imageView = itemView.findViewById(R.id.iv_login_bg);        }    }}

<?xml version="1.0" encoding="utf-8"?><ImageView xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/iv_login_bg"    android:layout_width="480dp"    android:layout_height="2065dp"    android:scaleType="matrix"    android:adjustViewBounds="true"    android:background="@drawable/login_bg01"/>

public class LoginActivity extends AppCompatActivity {    private AutoPollRecyclerView recyclerView;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_login);        recyclerView = findViewById(R.id.recyclerview);
        recyclerView.setLayoutManager(                new LinearLayoutManager(                        this,                        //设置LinearLayoutManager.HORIZONTAL  则水平滚动                        LinearLayoutManager.VERTICAL, false));
            AutoPollAdapter autoPollAdapter = new AutoPollAdapter(getApplicationContext());            recyclerView.setAdapter(autoPollAdapter);            //启动滚动            recyclerView.start();    }}

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent">

    <com.imooc.guessmusic.view.AutoPollRecyclerView        android:id="@+id/recyclerview"        android:layout_width="match_parent"        android:layout_height="wrap_content"        tools:ignore="MissingConstraints" />
    <ImageView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:scaleType="fitXY"        android:src="@drawable/login_dark" />
    <ImageView        android:layout_width="120dp"        android:layout_height="120dp"        android:layout_gravity="center_horizontal"        android:layout_marginTop="120dp"        android:src="@drawable/login_logo" />
    <TextView        android:layout_width="400dp"        android:layout_height="60dp"        android:layout_marginTop="60dp"        android:layout_gravity="center"        android:background="@drawable/btn_c"        android:gravity="center"        android:textSize="22sp"        android:textStyle="bold"        android:textColor="@color/black"        android:text="微信登录" />    <TextView        android:layout_width="400dp"        android:layout_height="60dp"        android:layout_marginTop="150dp"        android:layout_gravity="center"        android:background="@drawable/btn_c_b"        android:gravity="center"        android:textSize="22sp"        android:textColor="@color/text_white"        android:text="手机号码快捷登录" /></FrameLayout>