java - 使横幅图像自动滚动 - Android-Java

Question

我有一组横幅图像，当用户滑动它时可以滑动，并且触摸图像将重定向到某个网站。我想向横幅图像添加自动滚动，但我不太确定该怎么做，有人可以帮我看一下下面的代码吗？

public class MyAdapter extends InfinitePagerAdapter {
    BannerPagerAdapter pagerAdapter;
    AutoScrollViewPager viewPager;
    public static ArrayList<HashMap<String,String>> bannerAry = new ArrayList<HashMap<String,String>>();

public void onCreate(Bundle savedInstanceState) {
    // Home header banner
    LayoutInflater inflater = getLayoutInflater();
    header = inflater.inflate(R.layout.home_banner, null);
    if (homeBanner.equalsIgnoreCase("enable") && bannerAry.size() > 0){
        gridView.addHeaderView(header);
    }

    viewPager = (AutoScrollViewPager) header.findViewById(R.id.view_pager);
    pageIndicator = (LinePageIndicator) header.findViewById(R.id.indicator);

    display = this.getWindowManager().getDefaultDisplay();

    float scale = (float) display.getWidth() / Constants.HOME_BANNER_WIDTH;
    int newHeight = (int) Math.round(Constants.HOME_BANNER_HEIGHT * scale);
    viewPager.getLayoutParams().height = newHeight;
    pagerAdapter = new BannerPagerAdapter(this, bannerAry);
    viewPager.setAdapter(pagerAdapter);
    pageIndicator.setViewPager(viewPager);
    viewPager.addOnPageChangeListener(mOnPageChangeListener);

class BannerPagerAdapter extends PagerAdapter {
    Context context;
    LayoutInflater inflater;
    ArrayList<HashMap<String,String>> data;


    public BannerPagerAdapter(Context act, ArrayList<HashMap<String,String>> newary) {
        this.data = newary;
        this.context = act;
    }

    public int getCount() {
        return data.size();
    }

    public Object instantiateItem(ViewGroup collection, final int position) {
        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View itemView = inflater.inflate(R.layout.banner_image,
                collection, false);

        ImageView image = (ImageView) itemView.findViewById(R.id.image);
        String img = data.get(position).get("image");
        Log.v("banner img", "img="+img);
        if (!img.equals("")){
            Picasso.with(FragmentMainActivity.this).load(img).into(image);
        }

        image.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (Patterns.WEB_URL.matcher(data.get(position).get("url")).matches()) {
                    Intent b = new Intent(Intent.ACTION_VIEW, Uri.parse(data.get(position).get("url")));
                    startActivity(b);
                } else {
                    Toast.makeText(FragmentMainActivity.this, getString(R.string.url_invalid), Toast.LENGTH_SHORT).show();
                }
            }
        });

        ((ViewPager) collection).addView(itemView, 0);

        return itemView;

    }

    @Override
    public void destroyItem(View arg0, int arg1, Object arg2) {
        ((ViewPager) arg0).removeView((View) arg2);
    }

    @Override
    public boolean isViewFromObject(View arg0, Object arg1) {
        return arg0 == ((View) arg1);

    }

    @Override
    public Parcelable saveState() {
        return null;
    }
}

ViewPager.OnPageChangeListener mOnPageChangeListener = new ViewPager.OnPageChangeListener() {

    @Override
    public void onPageScrollStateChanged(int state) {
        enableDisableSwipeRefresh( state == ViewPager.SCROLL_STATE_IDLE );

    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {

    }

    @Override
    public void onPageSelected(int position) {

    }
};

private void enableDisableSwipeRefresh(boolean enabled){
    if (enabled) {
        swipeLayout.setEnabled(true);
    } else {
        swipeLayout.setEnabled(false);
    }
}

Answer 1

您可以通过使用 TimerTask 来做到这一点，您可以在其中安排具有一定持续时间间隔的滚动事件，您需要在初始化 viewPager 和 pagerAdapter 后调用此方法，代码如下:

private void startAutoScrolling() {

    stopAutoScrolling();
    TimerTask task = new TimerTask() {
        @Override
        public void run() {
          if(activityContext!=null)
                activityContext.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        int position = (viewPager.getCurrentItem() + 1) % pagerAdapter.getCount();
                        viewPager.setCurrentItem(position);
                    }
                });

        }
    };

    timer = new Timer();
    timer.scheduleAtFixedRate(task, 3000, 3000);
}

这里使用 stopAutoScrolling() 方法来确保停止之前运行的 TimerTask 进行自动滚动，如果用户在按下主页按钮或接听电话后返回到应用程序，可能会出现这种情况。

    public void stopAutoScrolling() {
    Log.i(TAG, "stop auto scroll of viewpager");
    if (timer != null)
        timer.cancel();
}