Question

编辑：解决了......大部分时间。在getView（）中调用Lod.g（...）仍然没有出现在LogCat中，但一切似乎都在工作。以下代码已更新为工作版本。

我的ArrayAdapter类：

public class PostAdapter extends ArrayAdapter<Post> {

//fields
private LayoutInflater inflater;
private ArrayList<Post> posts;

//constructor
public PostAdapter(Context context, ArrayList<Post> posts) {
    super(context, R.layout.post_layout, R.id.title, posts);
    this.inflater = LayoutInflater.from(context);
    this.posts = posts;
}

//methods
@Override
public View getView(int position, View convertView, ViewGroup parent) {
    //get data item for this position
    Post post = (Post)getItem(position);
    //check if existing view is being reused, otherwise inflate the view
    if(convertView == null) {
        convertView = inflater.inflate(R.layout.post_layout, parent, false);
    }
    //Populate views with data
    TextView title = (TextView) convertView.findViewById(R.id.title);
    title.setText(post.getTitle());
    TextView subTitle = (TextView) convertView.findViewById(R.id.subTitle);
    subTitle.setText(post.getDescription());

    //return completed view to render on screen
    return convertView;
}

@Override
public int getCount() {
    return posts.size();
}

}

我创建ArrayAdapter的代码：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_screen);

    //Initializing feed variables
    posts = new ArrayList<>();
    postAdapter = new PostAdapter(this, posts);
    list = (ListView) findViewById(R.id.list);

    //attaching Adapter to ListView
    list.setAdapter(postAdapter);

    DatabaseReference p = database.getReference("posts");
    p.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            //get reference to post
            HashMap<Object, Object> entry = (HashMap<Object, Object>) dataSnapshot.getValue();

            //convert to Post.class datatype
            Post post = new Post();
            if (entry.get("category") != null) { post.setCategory(entry.get("category").toString()); }
            if (entry.get("title") != null) { post.setTitle(entry.get("title").toString()); }
            if (entry.get("description") != null) { post.setDescription(entry.get("description").toString()); }
            if (entry.get("hasImg") != null) { post.setImg((boolean)entry.get("hasImg")); }
            if (entry.get("postKey") != null) { post.setPostKey(entry.get("postKey").toString()); }
            if (entry.get("posterID") != null) { post.setPosterID(entry.get("posterID").toString()); }
            if (entry.get("schoolID") != null) { post.setSchoolID(entry.get("schoolID").toString()); }
            if (entry.get("flagged") != null) { post.setFlagged((long)entry.get("flagged")); }
            if (entry.get("time") != null) { post.setTime((long)entry.get("time")); };

            //add to ArrayList
            posts.add(post);
            postAdapter.notifyDataSetChanged();

            Log.d("LIST", "Post Added: Posts: " + postAdapter.getCount());
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

Answer 1

#List adapter is getting initialized with zero posts elements.
#list.setAdapter(postAdapter) : put into childAdded listener.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_screen);

    //retrieve post data from firebase
    posts = new ArrayList<>();

    //ListView and PostAdapter
    list = (ListView) findViewById(R.id.list);
    postAdapter = new PostAdapter(this, posts);

    DatabaseReference p = database.getReference("posts");
    p.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            //get reference to post
            HashMap<Object, Object> entry = (HashMap<Object, Object>) dataSnapshot.getValue();

            //convert to Post.class datatype
            Post post = new Post();
            if (entry.get("category") != null) { post.setCategory(entry.get("category").toString()); }
            if (entry.get("title") != null) { post.setTitle(entry.get("title").toString()); }
            if (entry.get("description") != null) { post.setDescription(entry.get("description").toString()); }
            if (entry.get("hasImg") != null) { post.setImg((boolean)entry.get("hasImg")); }
            if (entry.get("postKey") != null) { post.setPostKey(entry.get("postKey").toString()); }
            if (entry.get("posterID") != null) { post.setPosterID(entry.get("posterID").toString()); }
            if (entry.get("schoolID") != null) { post.setSchoolID(entry.get("schoolID").toString()); }
            if (entry.get("flagged") != null) { post.setFlagged((long)entry.get("flagged")); }
            if (entry.get("time") != null) { post.setTime((long)entry.get("time")); };

            //add to ArrayList
            posts.add(post);
            postAdapter.add(post);

             //attaching Adapter to ListView
            list.setAdapter(postAdapter);
            Log.d("LIST", "Item count: " + postAdapter.getCount());

            postAdapter.notifyDataSetChanged();
            Log.d("LIST", "Post Added: Posts: " + postAdapter.getCount());

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    }
}

Answer 2

事实证明问题与我正在使用的ContraintLayout有关。对格式和列表进行了一些调整。我已更新代码以反映我现在的工作实现。有趣的是，我在getView（）内部的Log.d（...）调用仍然没有出现，即使一切正常，getView 必须被调用。仍然不确定如何解释那个。

Android 2.3自定义ArrayAdapter getView方法未被调用

2 个答案: