Question

我有一个listview，我从数据库填充。

列表视图需要一些时间（<300毫秒）来填充列表。

如果我在 onActivityCreated 函数上执行 smoothScrollToPosition ，它什么都不做。

在OnCreate函数上，我必须等待〜200ms才能调用smoothScrollToPosition，在此之前，即使ListView对象也没有初始化。

我可以使用如下的getViewTreeObserver运行正常，但它需要最小的sdk版本16.我试图让它适用于版本14~15。

mListView.getViewTreeObserver().addOnGlobalLayoutListener(
            new ViewTreeObserver.OnGlobalLayoutListener() {
                @Override
                public void onGlobalLayout() {
                    mListView.smoothScrollToPosition(adapter.getCount());
                    // unregister listener (this is important)
                    mListView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                }
            });

我正在使用的代码 -

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    list = new ArrayList<Chat>();

    db = new DBAdapter(getContext());
    adapter = new CustomChatAdapter(getContext(), list);

    Log.d("ListView1", "Value of f: " + f);


    thread=  new Thread(){
        @Override
        public void run(){
            try {
                synchronized(this){
                    wait(200);
                }
            }
            catch(InterruptedException ex){
                Log.d("ListView1", "Interrupted Exception: " +ex.toString());
            }
            Log.d("ListView1", "Adapter Count: " +adapter.getCount());
            mListView.smoothScrollToPosition(adapter.getCount());
        }
    };

    getMsg("1", getActivity().getIntent().getStringExtra("key"));
    thread.start();
    Log.d("ListView1", "Adapter Count: " +adapter.getCount());

    //mListView.smoothScrollToPosition(adapter.getCount());

}



public void getMsg(String myid, String friend_id) {
    list.clear();
    try {
        Cursor cur = db.get_friend_shouts(myid,friend_id);
        String img_id1 = "";
        String img_id2 ="";
        if (cur != null) {
            if (cur.moveToFirst()) {
                do {
                    img_id1 = cur.getString(cur.getColumnIndex("image_id"));
                    img_id1 = img_id1 == null ? "null" : img_id1;
                    img_id2 = cur.getString(cur.getColumnIndex("r_img_id"));
                    img_id2 = img_id2 == null ? "null" : img_id2;
                    list.add(new Chat( img_id1 , cur.getString(cur.getColumnIndex("firstname")) + " " + cur.getString(cur.getColumnIndex("lastname")), cur.getString(cur.getColumnIndex("user_id")),
                             cur.getString(cur.getColumnIndex("shout_msg")) ,
                            img_id2, cur.getString(cur.getColumnIndex("r_firstname")) + " " + cur.getString(cur.getColumnIndex("r_lastname")) , cur.getString(cur.getColumnIndex("r_user_id")) , cur.getString(cur.getColumnIndex("rec_time"))  ));
                    //Log.d("ListView1", "User details: " + cur.getString(cur.getColumnIndex("user_id")) + " " + cur.getString(cur.getColumnIndex("firstname")) + cur.getString(cur.getColumnIndex("lastname")) + " " + cur.getString(cur.getColumnIndex("image_id")));
                } while (cur.moveToNext());
            }
        }
        adapter.notifyDataSetChanged();

        if(mListView!=null)
            mListView.smoothScrollToPosition(adapter.getCount());
    } catch (Exception e) {
        Log.d("ListView1", "getMsg Error: " + e.toString());
    }
}

ArrayAdapter类 -

public class CustomChatAdapter extends ArrayAdapter<Chat> {

private final Context context;
private final List<Chat> list;

public CustomChatAdapter(Context context, ArrayList<Chat> presidents) {
    super(context, R.layout.chatrowlayout, presidents);
    this.context = context;
    this.list = presidents;
}

static class ViewContainer {        public ImageView imageView;        public TextView txtMsg;    public ImageView imageView1;   public TextView txtTime;     }


@Override
public View getView(int position, View view, ViewGroup parent) {
    ViewContainer viewContainer;
    View rowView = view;
    //---print the index of the row to examine---
    //Log.d("ListView1",String.valueOf(position));
    //if(rowView == null) {
    viewContainer = new ViewContainer();
    LayoutInflater inflater = LayoutInflater.from(context);
    rowView= inflater.inflate(R.layout.chatrowlayout, null, true);
    viewContainer.txtMsg = (TextView) rowView.findViewById(R.id.msgText);
    viewContainer.imageView = (ImageView) rowView.findViewById(R.id.icon1);
    viewContainer.imageView1 = (ImageView) rowView.findViewById(R.id.icon2);
    viewContainer.txtTime = (TextView) rowView.findViewById(R.id.timeText);
    rowView.setTag(viewContainer);
    /*} else {
        viewContainer = (ViewContainer) rowView.getTag();
    }*/
    viewContainer.txtMsg.setText(list.get(position).getMsg());
    viewContainer.txtTime.setText(list.get(position).getMsg_time());

    if(list.get(position).getS_id().equals("1")) {

        viewContainer.imageView.setImageBitmap(BitmapFactory.decodeFile(new Info().p + File.separator+ "image_" + list.get(position).getPic_id1() + ".jpeg" ));
        viewContainer.imageView1.setAlpha(0);
        viewContainer.txtMsg.setGravity(Gravity.LEFT);
    } else {

        viewContainer.imageView1.setImageBitmap(BitmapFactory.decodeFile(new Info().p + File.separator+ "image_" + list.get(position).getPic_id1() + ".jpeg" ));
        viewContainer.imageView.setAlpha(0);
        viewContainer.txtMsg.setGravity(Gravity.RIGHT);
    }
    return rowView;
}

}

Answer 1

对于SDK 16之前的

removeGlobalOnLayoutListerner，addOnGlobalLayout适用于16之前。

Answer 2

OnCreate太早了。

您应该等待布局膨胀。 onResume中的平滑滚动应该可以解决问题：

@Override
protected void onResume() {
   mListView.smoothScrollToPosition(adapter.getCount());
}

Ready或on Initialized监听器上的Android ListView

2 个答案: