Question

MainActivity类

我在将适配器设置为recyclerview时遇到错误在logcat中它显示调用空指针引用

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    RecyclerView recyclerView;

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

        recyclerView = (RecyclerView) findViewById(R.id.postList);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        //fetch data
        Call<PostList> postList = BloggerApi.getService().getPostList(url);
        postList.enqueue(new Callback<PostList>() {
            @Override
            public void onResponse(Call<PostList> call, Response<PostList> response) {
                PostList list = response.body();
                recyclerView.setAdapter(new PostAdapter(MainActivity.this, list.getItems()));
                Toast.makeText(MainActivity.this, "success", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onFailure(Call<PostList> call, Throwable t) {
                Toast.makeText(MainActivity.this, "Failed", Toast.LENGTH_SHORT).show();
            }
        });
    }

PostAdapter类

public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostViewHolder> {

    private Context context;
    private List<Item> items;

    public PostAdapter(Context context, List<Item> items) {
        this.context = context;
        this.items = items;
    }

    @Override
    public PostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.post_item, parent, false);
        return new PostViewHolder(view);
    }

    @Override
    public void onBindViewHolder(PostViewHolder holder, int position) {
        Item item = items.get(position);
        holder.postTitle.setText(item.getTitle());
        holder.postDescription.setText(item.getContent());
    }

    @Override
    public int getItemCount() {
        return items.size();
    }

    public class PostViewHolder extends RecyclerView.ViewHolder{

        ImageView postImage;
        TextView postTitle;
        TextView postDescription;

        public PostViewHolder(View itemView) {
            super(itemView);

            postImage = (ImageView) itemView.findViewById(R.id.postImage);
            postTitle = (TextView) itemView.findViewById(R.id.postTitle);
            postDescription = (TextView) itemView.findViewById(R.id.postDescription);

        }
    }
}

Answer 1

尝试

public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostViewHolder> {

我假设您现有的行刚刚被排除在代码格式标记之外。

尝试在空对象引用上调用虚方法

1 个答案: