2020年5月2日 14:52:30go评论85阅读模式

英文:

java.lang.NumberFormatException: null in onBindViewHolder

问题

这是我翻译的内容：

我正在制作一个聊天应用，但当我点击发送按钮时出现了这个错误...请问有人能解释一下 "null" 是什么意思，以及为什么会出现这个错误吗？因为这不是第一次发生了，这真的让我很烦恼...如果你能帮助我就请帮帮我吧。

public class AdapterChat extends RecyclerView.Adapter<AdapterChat.MyHolder> /* 这段代码是第二个错误 */
{
    private static final int MSG_TYPE_LEFT = 0;
    private static final int MSG_TYPE_RIGHT = 1;
    Context context;
    List<Modelchat> chatList;
    String imageUrl;
    FirebaseUser fUser;

    public AdapterChat(Context context, List<Modelchat> chatList, String imageUrl) {
        this.context = context;
        this.chatList = chatList;
        this.imageUrl = imageUrl;
    }

    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        if (i == MSG_TYPE_RIGHT) {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, viewGroup, false);
            return new MyHolder(view);
        } else {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, viewGroup, false);
            return new MyHolder(view);
        }
    }

    @Override
    public void onBindViewHolder(@NonNull MyHolder myHolder, int i) {
        String message = chatList.get(i).getMessage();
        String timeStamp = chatList.get(i).getTimestamp();

        Calendar cal = Calendar.getInstance(Locale.ENGLISH);
        cal.setTimeInMillis(Long.parseLong(timeStamp)); /* 这段代码是第一个错误 */
        String dataTime = android.text.format.DateFormat.format("dd/MM/yyyy hh:mm aa", cal).toString();

        myHolder.messageTv.setText(message);
        myHolder.timeTv.setText(dataTime);
        try {
            Picasso.get().load(imageUrl).into(myHolder.profileTv);
        } catch (Exception e) {

        }

        if (i == chatList.size()-1) {
            if (chatList.get(i).isSeen()) {
                myHolder.isSeenTv.setText("已查看");
            } else {
                myHolder.isSeenTv.setText("已送达");
            }
        } else {
            myHolder.isSeenTv.setVisibility(View.GONE);
        }
    }

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

    @Override
    public int getItemViewType(int position) {
        fUser = FirebaseAuth.getInstance().getCurrentUser();
        if (chatList.get(position).getSender().equals(fUser.getUid())) {
            return MSG_TYPE_RIGHT;
        } else {
            return MSG_TYPE_LEFT;
        }
    }

    class MyHolder extends RecyclerView.ViewHolder {

        ImageView profileTv;
        TextView messageTv, timeTv, isSeenTv;

        public MyHolder(@NonNull View itemView) {
            super(itemView);

            profileTv = itemView.findViewById(R.id.profileTv);
            messageTv = itemView.findViewById(R.id.messageTv);
            timeTv = itemView.findViewById(R.id.timeTv);
            isSeenTv = itemView.findViewById(R.id.isSeenTv);
        }
    }
}

错误信息：

java.lang.NumberFormatException: null

    at cm.example.learno.SocialApp.adapters.AdapterChat.onBindViewHolder(AdapterChat.java:56)
    at com.example.learno.SocialApp.adapters.AdapterChat.onBindViewHolder(AdapterChat.java:23)

我在错误的代码旁边添加了注释

英文:

I am making a chat app but when I click send button this error occur .. and please can any one explain to me what is meaning of null and why it happens ? because it is not first time and is is a really annoying to me .. please help me if you can..

 public class AdapterChat extends RecyclerView.Adapter&lt;AdapterChat.MyHolder&gt; /* this code is second error */
{
private static final int MSG_TYPE_LEFT = 0;
private static final int MSG_TYPE_RIGHT = 1;
Context context;
List&lt;Modelchat&gt; chatList;
String imageUrl;
FirebaseUser fUser;
public AdapterChat(Context context, List&lt;Modelchat&gt; chatList, String imageUrl) {
this.context = context;
this.chatList = chatList;
this.imageUrl = imageUrl;
}
@NonNull
@Override
public MyHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
if (i == MSG_TYPE_RIGHT) {
View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, viewGroup, false);
return new MyHolder(view);
} else {
View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, viewGroup, false);
return new MyHolder(view);
}
}
@Override
public void onBindViewHolder(@NonNull MyHolder myHolder, int i) {
String message = chatList.get(i).getMessage();
String timeStamp = chatList.get(i).getTimestamp();
Calendar cal = Calendar.getInstance(Locale.ENGLISH);
cal.setTimeInMillis(Long.parseLong(timeStamp)); /* this code is first error*/
String dataTime = android.text.format.DateFormat.format(&quot;dd/MM/yyyy hh:mm aa&quot;, cal).toString();
myHolder.messageTv.setText(message);
myHolder.timeTv.setText(dataTime);
try {
Picasso.get().load(imageUrl).into(myHolder.profileTv);
} catch (Exception e) {
}
if (i == chatList.size()-1) {
if (chatList.get(i).isSeen()) {
myHolder.isSeenTv.setText(&quot;Seen&quot;);
} else {
myHolder.isSeenTv.setText(&quot;Delivered&quot;);
}
} else {
myHolder.isSeenTv.setVisibility(View.GONE);
}
}
@Override
public int getItemCount() {
return chatList.size();
}
@Override
public int getItemViewType(int position) {
fUser = FirebaseAuth.getInstance().getCurrentUser();
if (chatList.get(position).getSender().equals(fUser.getUid())) {
return MSG_TYPE_RIGHT;
} else {
return MSG_TYPE_LEFT;
}
}
class MyHolder extends RecyclerView.ViewHolder {
ImageView profileTv;
TextView messageTv, timeTv, isSeenTv;
public MyHolder(@NonNull View itemView) {
super(itemView);
profileTv = itemView.findViewById(R.id.profileTv);
messageTv = itemView.findViewById(R.id.messageTv);
timeTv = itemView.findViewById(R.id.timeTv);
isSeenTv = itemView.findViewById(R.id.isSeenTv);
}
}
}

Error message

 java.lang.NumberFormatException: null
at cm.example.learno.SocialApp.adapters.AdapterChat.onBindViewHolder(AdapterChat.java:56)
at com.example.learno.SocialApp.adapters.AdapterChat.onBindViewHolder(AdapterChat.java:23)

i am made a comment beside the wrong code

答案1

得分: 3

尝试将

String timeStamp = chatList.get(i).getTimestamp();

更改为

String timeStamp = chatList.get(myHolder.getAdapterPosition()).getTimestamp();

您正在尝试解析空值时间戳 timeStamp 到

cal.setTimeInMillis(Long.parseLong(timeStamp));

至于什么是 null，请花些时间进行研究和阅读。您可以从这里开始。

英文:

try changing

String timeStamp = chatList.get(i).getTimestamp();

String timeStamp = chatList.get(myHolder.getAdapterPosition()).getTimestamp();

You are trying to parse null value timeStamp into

cal.setTimeInMillis(Long.parseLong(timeStamp));

As for what null is, please take the time to research and read on it. You can start here

答案2

得分: 0

使用 DateTimeFormatter 替代 DateFormat，如果您想要同时格式化日期和时间。
另一种修复方法是从格式化程序中移除时间，就像这样 dd/MM/yyyy。

英文:

Use DateTimeFormatter instead of DateFormat if you want to format date and time simultaneously.
Another way to fix that is remove time from formatter like this dd/MM/yyyy

通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。

java.lang.NumberFormatException: 在onBindViewHolder中为null

问题

答案1

答案2

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