Question

我有一个相对布局的Listview。如何从扩展Activity的ManActivity向ListView添加数据。如果我使用了扩展ListActivity的类，我可以使用adapter.notifyDataSetChanged（）。我猜。有什么建议？提前致谢

Message msg[] = new Message[]
                {
                    new Message(1, "Hello World", "Thank You"), new Message(1, "Hello World 2", "Thank You 2")
                };
adapter = new MyAdapter(context, R.layout.row, msg);
listview.setAdapter(adapter);

添加此选项会使我的应用崩溃

adapter.add(new Message(1, "Hello World3", "Thank You3"));

Logcat文字

07-07 20:22:53.680: E/AndroidRuntime(1512): FATAL EXCEPTION: AsyncTask #3
07-07 20:22:53.680: E/AndroidRuntime(1512): java.lang.RuntimeException: An error occured while executing doInBackground()
07-07 20:22:53.680: E/AndroidRuntime(1512):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.lang.Thread.run(Thread.java:856)
07-07 20:22:53.680: E/AndroidRuntime(1512): Caused by: java.lang.UnsupportedOperationException
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.AbstractList.add(AbstractList.java:404)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.AbstractList.add(AbstractList.java:425)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at android.widget.ArrayAdapter.add(ArrayAdapter.java:179)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at com.abhishek.ally2.chat.doInBackground(chat.java:28)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at com.abhishek.ally2.chat.doInBackground(chat.java:1)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-07 20:22:53.680: E/AndroidRuntime(1512):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-07 20:22:53.680: E/AndroidRuntime(1512):     ... 4 more

MyAdapter.java

package com.abhishek.ally2;

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyAdapter extends ArrayAdapter<Message>{
    private final Context context;
    private final Message data[];
    int layoutResourceId;

    public MyAdapter(Context context, int layoutResourceId, Message[] values) {
        // TODO Auto-generated constructor stub
        super(context, layoutResourceId, values);
        this.context = context;
        this.data = values;
        this.layoutResourceId = layoutResourceId;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        View row = convertView;
        MessageHolder holder = null;
        if(row == null)
        {
            LayoutInflater inflator = ((Activity)context).getLayoutInflater();
            row = inflator.inflate(layoutResourceId, parent, false);
            holder = new MessageHolder();
            holder.pic = (ImageView)row.findViewById(R.id.pic);
            holder.msg = (TextView)row.findViewById(R.id.msg);
            holder.time = (TextView)row.findViewById(R.id.time);
            row.setTag(holder);

        }
        else
        {
            holder = (MessageHolder)row.getTag();
        }
            Message message = data[position];
            holder.msg.setText(message.msg);
            holder.time.setText(message.time);

        return row;

    }


    static class MessageHolder {
        ImageView pic;
        TextView msg;
        TextView time;
    }
}

Answer 1

要将数据添加到列表视图，您需要向数据集添加数据，然后通过调用adapter.notifyDataSetChanged()来告知适配器数据集，如上所述。因此，要使列表工作，您需要数据集（即数组）listview（在布局中）和绑定这两个togeter的适配器（即ArrayAdapter）。您还需要通过调用list.setAdapter()告诉list其适配器的位置。 ListActivity只是一个帮助类，而不是一个要求，没有它，ListView的工作完全正常。

Answer 2

另外，对于marcins的回答，您可以通过已设置的适配器管理数据，方法是使用adapter.add(item)等直接向适配器添加/删除数据，以及用于创建适配器的基础列表（如果您使用过的话）将更新为，您无需担心通知。如果您向适配器添加任何观察者，notifyDataSetChanged()会更有意义。

修改

我无法对您的帖子发表评论，之后您又编辑了您的示例代码。因为您尝试从AsyncTask更新列表（据我所知，从堆栈跟踪），您必须调用runOnUiThread(Runnable r)

runOnUiThread(new Runnable() { @Override public void run() { adapter.add(new Message(1, "Hello World3", "Thank You3")); } });

<强> EDIT2：

您不需要在适配器中拥有值的成员，因为这些值已经是扩展arrayadapter的成员。要访问getView中的一条特定邮件，您可以致电getItem(position)。这样您就不需要覆盖listAdapter.add(T item)

Answer 3

这是一个例子：

Years years = readYearsList(); // return the Years array.

ListView listYears = (ListView)findViewById(R.id.list);
YearAdapter yearAdapter = new YearAdapter(MainActivity.this, R.layout.rowyears, years); // YearAdapter extends ArrayAdapter<Years>
listYears.setAdapter(yearAdapter);

在扩展Activity而不是ListActivity的类中向ListView添加数据

3 个答案: