Java 使用 Android 应用程序的自定义适配器将项目动态添加到列表视图

Dynamically add items to list view using custom adapter for Android app

提问by user1282637

So, right now I have a custom adapter class that takes in an array of Locations and adds them to a ListView. This is all fine and dandy, but I would like to add Locations to this listview after this initialization. For example, someone can "add a Location" and it will add it to this ListView. Here is my Main Activity:

所以，现在我有一个自定义适配器类，它接收一个位置数组并将它们添加到一个 ListView。这一切都很好，但我想在初始化后向这个列表视图添加位置。例如，有人可以“添加一个位置”，它会将它添加到这个 ListView。这是我的主要活动：

package com.example.listviewtest;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;

public class MainActivity extends Activity {

private ListView listView1;

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

    Location location_data[] = new Location[]
    {
        new Location(R.drawable.ic_launcher, "Location 1", "Fruit!", "2 miles", "8-4 mon-fri\nclosed sun"),
        new Location(R.drawable.ic_launcher, "Location 2", "Veggies!", "2 miles", "8-5"),
        new Location(R.drawable.ic_launcher, "Location 3", "Plants!", "2 miles", "8-5"),
        new Location(R.drawable.ic_launcher, "Location 4", "Flowers!", "2 miles", "8-5"),
        new Location(R.drawable.ic_launcher, "Location 5", "Baked Goods!", "2 miles", "8-5")
    };

   LocationAdapter adapter = new LocationAdapter(this, 
            R.layout.listview_item_row, location_data);

   //adapter.add(new Location(R.drawable.ic_launcher, "Location 6", "Veggies!", "2 miles", "8-5"));


    listView1 = (ListView)findViewById(R.id.listView1);

    View header = (View)getLayoutInflater().inflate(R.layout.listview_header_row, null);
    listView1.addHeaderView(header);

    listView1.setAdapter(adapter);
}
}

This works. I want to now do something like adapter.add(new Location(R.drawable.ic_launcher, "Location 6", "Veggies!", "2 miles", "8-5"));AFTER filling it with the array.

这有效。我现在想在adapter.add(new Location(R.drawable.ic_launcher, "Location 6", "Veggies!", "2 miles", "8-5"));用数组填充它之后做一些事情。

Here is my LocationAdapter class:

这是我的 LocationAdapter 类：

package com.example.listviewtest;

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 LocationAdapter extends ArrayAdapter<Location>{

Context context; 
int layoutResourceId;    
Location data[] = null;

public LocationAdapter(Context context, int layoutResourceId, Location[] data) {
    super(context, layoutResourceId, data);
    this.layoutResourceId = layoutResourceId;
    this.context = context;
    this.data = data;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    LocationHolder holder = null;

    if(row == null)
    {
        LayoutInflater inflater = ((Activity)context).getLayoutInflater();
        row = inflater.inflate(layoutResourceId, parent, false);

        holder = new LocationHolder();
        holder.imgIcon = (ImageView)row.findViewById(R.id.imgIcon);
        holder.txtTitle = (TextView)row.findViewById(R.id.txtTitle);
        holder.details = (TextView)row.findViewById(R.id.details);
        holder.distance = (TextView)row.findViewById(R.id.distance);
        holder.hours = (TextView)row.findViewById(R.id.hours);

        row.setTag(holder);
    }
    else
    {
        holder = (LocationHolder)row.getTag();
    }

    Location location = data[position];
    holder.txtTitle.setText(location.title);
    holder.imgIcon.setImageResource(location.icon);
    holder.details.setText(location.details);
    holder.distance.setText(location.distance);
    holder.hours.setText(location.hours);

    return row;
}

static class LocationHolder
{
    ImageView imgIcon;
    TextView txtTitle;
    TextView details;
    TextView distance;
    TextView hours;
}
}

Any ideas on how I can implement this? Thanks.

关于如何实现这一点的任何想法？谢谢。

采纳答案by LordRaydenMK

1. In your adapter change the Locations data[]from array to ArrayList<Location>and override the appropriate constructor
2. In your activity, make your variable dataa field (type ArrayList<Location>)
3. When you add a location you can use data.add(location)
4. Then you can call notifyDatasetChanged()on your adapter

1. 在您的适配器中，将Locations data[]from 数组更改为 ArrayList<Location>并覆盖相应的构造函数
2. 在您的活动中，让您的变量data成为一个字段（类型ArrayList<Location>）
3. 添加位置时，您可以使用 data.add(location)
4. 然后你可以调用notifyDatasetChanged()你的适配器

Example code.

示例代码。

回答by bstar55

In your main activity, I'd recommend using an ArrayList< Location > rather than Location[] to make it easier to add new Location elements. Then, rather than having LocationAdapter extend ArrayAdapter< Location >, have it extend ListAdapter< Location > so you can pass your ArrayList< Location > to it.

在您的主要活动中，我建议使用 ArrayList< Location > 而不是 Location[] 以便更轻松地添加新的 Location 元素。然后，与其让 LocationAdapter 扩展 ArrayAdapter< Location >，不如让它扩展 ListAdapter< Location > 以便您可以将 ArrayList< Location > 传递给它。

That said, all you need to do in your addLocation(Location l) method in your MainActivity, is add an element to either the Location[] or ArrayList< Location > data structure you passed to your adapter, and then call:

也就是说，您需要在 MainActivity 的 addLocation(Location l) 方法中做的就是向传递给适配器的 Location[] 或 ArrayList< Location > 数据结构添加一个元素，然后调用：

adapter.notifyDataSetChanged();

Note that you'll need to make your adapter a member variable in your MainActivity to allow access outside of your onCreate().

请注意，您需要将适配器设为 MainActivity 中的成员变量，以允许在 onCreate() 之外进行访问。

回答by Engineero

Store your data in an ArrayList<Location>instead of just Location[], and then make a public class in your list adapter:

将您的数据存储在一个ArrayList<Location>而不是 just 中Location[]，然后在您的列表适配器中创建一个公共类：

ArrayList<Location> data = new ArrayList<Location>();

@Override
public void add(Location location) {
    data.add(location);
    notifyDataSetChanged();
}

Then, when you want to add an item to the list, just call location_data.add(new_location).

然后，当您想向列表中添加项目时，只需调用location_data.add(new_location).

Edit:It looks like you have your pick from several mostly identical answers.

编辑：看起来您可以从几个几乎相同的答案中进行选择。

回答by sotrh

Looks like you need to override the add method in your LocationAdapter class to add the object to the internal list

看起来您需要覆盖 LocationAdapter 类中的 add 方法才能将对象添加到内部列表中

@Override
public void add(Location location)
{
    super.add(location);
    data.add(location);
}

This implementation requires that you change data to an ArrayList instead of just an array, otherwise you would have to code the array re-sizing yourself.

此实现要求您将数据更改为 ArrayList 而不仅仅是数组，否则您必须自己编写代码重新调整数组大小。

ArrayList<Location> data = null; // Alternatively use new ArrayList<Location>();

If you don't do this, the internal data will remain unchanged and a call to add will do not change the list. This is bad because you use the data variable to get the values for the views.

如果不这样做，内部数据将保持不变，调用 add 不会更改列表。这很糟糕，因为您使用数据变量来获取视图的值。