Android适配器上下文

Question

Android Dev的新事物，并尝试在应用程序适配器中获得上下文，但我一直却获得了无异常。我尝试将URL字符串加载到Glide中，但glide.with(context)不起作用。该应用程序从sqlite中提取值（此部分正常），我现在正在尝试获取其中一个值（URL），并通过Glide将其设置为ImageView。XML具有所需的所有视图。

错误：您不能在com.bumptech.glide.manager.requestmanagerretriever.get

上启动null上下文上的负载

userdapter.java

public class UsersAdapter extends RecyclerView.Adapter<UsersAdapter.UserViewHolder> {
private ArrayList<User> mDataSet;
public UsersAdapter(ArrayList<User> mDataSet) {
    this.mDataSet = mDataSet;
}
@Override
public UserViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.activity_favorites2, parent, false);
    UserViewHolder userViewHolder = new UserViewHolder(v);
    return userViewHolder;
}
@Override
public void onBindViewHolder(UserViewHolder holder, int position) {
    holder.name_entry.setText(mDataSet.get(position).getName());
    holder.email_entry.setText(mDataSet.get(position).getEmail());
    holder.icon_entry.setText(""+mDataSet.get(position).getName().charAt(0));
    String name = mDataSet.get(position).getName();
    String url = mDataSet.get(position).getEmail();
    // load image into imageview using glide
    Glide.with(context)
            .load(url)
            .asBitmap()
            .placeholder(R.drawable.ic_blank)
            .error(R.drawable.ic_blank)
            .into(holder.ivFavorites);
}
@Override
public int getItemCount() {
    return mDataSet.size();
}
public class UserViewHolder extends RecyclerView.ViewHolder {
    CardView cardView;
    TextView name_entry, email_entry, icon_entry;
    ImageView ivFavorites;
    UserViewHolder(View itemView) {
        super(itemView);
        cardView = (CardView) itemView.findViewById(R.id.user_layout);
        name_entry = (TextView) itemView.findViewById(R.id.name_entry);
        email_entry = (TextView) itemView.findViewById(R.id.email_entry);
        icon_entry = (TextView) itemView.findViewById(R.id.icon_entry);
        ivFavorites = (ImageView) itemView.findViewById(R.id.ivFavorites);
    }
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
    super.onAttachedToRecyclerView(recyclerView);
}
}

阅读有关适配器和上下文的信息，我尝试了以下内容，但成功最少。

public class UsersAdapter extends      RecyclerView.Adapter<UsersAdapter.UserViewHolder> {
private ArrayList<User> mDataSet;
private Context context;
public UsersAdapter(ArrayList<User> mDataSet) {
    this.mDataSet = mDataSet;
}
public UsersAdapter(ArrayList<User> mDataSet, Context context) {
    this.context = context;
}

我的 fairite.java 活动从sqlite中拉出值并在cardView中显示它们（尽管我无法滑动来加载图像）：

>

公共类的收藏夹扩展了appCompatactivity {

private RecyclerView recyclerView;
private LinearLayoutManager layoutManager;
private UsersAdapter adapter;
private DBHandler dbHandler;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_favorites);
    recyclerView = (RecyclerView) findViewById(R.id.usersList);
    recyclerView.setHasFixedSize(true);
    layoutManager = new GridLayoutManager(this,2);
    recyclerView.setLayoutManager(layoutManager);
    dbHandler = new DBHandler(Favorites.this);
    Log.d("Reading: ", "reading contacts..");
    ArrayList<User> users = dbHandler.getAllUsers();
    adapter = new UsersAdapter(users);
    recyclerView.setAdapter(adapter);
    adapter.notifyDataSetChanged();
}

}

Answer 1

初始化适配器时通过上下文

adapter = new UsersAdapter(users,getApplicationContext());

在您的适配器中，实现等效构造函数

public UsersAdapter(ArrayList<User> mDataSet, Context context) {
    this.context = context;
    this.mDataSet = mDataSet;
}