我有一个问题，我正在尝试解决。我创建了一个包含三个项目的列表，它还允许您按照本教程将图像添加到列表中......
在这里，按顺序，是我所做的。1. 我首先创建了一个名为"Item"的类来充当列表项的模型。
public class Item
{
public int Id;
public String IconFile;
public String Name;
public Item(int id, String iconFile, String name
{
Id = id;
IconFile = iconFile;
Name = name;
}
}
。阿拉伯数字。然后，我创建了一个名为"Model"的类，为我的项目提供 ArrayList。但是，我不是简单地将文本放在列表名称中，而是包含全局变量。
http://www.debugrelease.com/2013/06/24/android-listview-tutorial-with-images-and-text/
public class Model extends Globals
{
public static ArrayList<Item> Items;
public static void LoadModel()
{
Items = new ArrayList<Item>();
Items.add(new Item(1, "temperature_icon.png", "Temperature/Humidity" + temperature + "°C / " + humidity + "%"));
Items.add(new Item(2, "gas_icon.png", "LPG" + lpg +" ppm"));
Items.add(new Item(3, "alcohol_icon.png", "Alcohol" + alcohol + " ppm"));
}
public static Item GetbyId(int id)
{
for(Item item : Items)
{
if (item.Id == id)
{
return item;
}
}
return null;
}
}
3.（额外步骤）我添加了一个全局类来访问全局变量。
public abstract class Globals extends Activity
{
static int temperature;
static int humidity;
static int lpg;
static int alcohol;
}
4.将列表视图小部件添加到主活动布局。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/listView" />
</LinearLayout>
5.添加自定义布局，因为我显示的不仅仅是文本。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:minHeight="64dp">
<ImageView
android:id="@+id/imageView"
android:layout_width="32dp"
android:layout_height="32dp"
android:layout_alignParentLeft="true"
android:layout_marginLeft="9dp"
android:layout_alignParentTop="true"/>
<TextView
android:layout_alignBottom="@+id/imageView"
android:layout_width="97dp"
android:layout_height="32dp"
android:id="@+id/textView"
android:layout_alignParentLeft="true"
android:layout_marginLeft="66dp"
android:layout_alignParentRight="true"
android:gravity="center_vertical"/>
</RelativeLayout>
6.创建自定义适配器以显示数据
public class ItemAdapter extends ArrayAdapter<String> {
private final Context context;
private final String[] Ids;
private final int rowResourceId;
public ItemAdapter(Context context, int textViewResourceId, String[] objects) {
super(context, textViewResourceId, objects);
this.context = context;
this.Ids = objects;
this.rowResourceId = textViewResourceId;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(rowResourceId, parent, false);
ImageView imageView = (ImageView) rowView.findViewById(R.id.imageView);
TextView textView = (TextView) rowView.findViewById(R.id.textView);
int id = Integer.parseInt(Ids[position]);
String imageFile = Model.GetbyId(id).IconFile;
textView.setText(Model.GetbyId(id).Name);
// get input stream
InputStream ims = null;
try {
ims = context.getAssets().open(imageFile);
} catch (IOException e) {
e.printStackTrace();
}
// load image as Drawable
Drawable d = Drawable.createFromStream(ims, null);
// set image to ImageView
imageView.setImageDrawable(d);
return rowView;
}
}
7.加载模型，查找列表视图并在主活动中分配适配器。
public class MainActivity extends Globals
{
ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Model.LoadModel();
listView = (ListView) findViewById(R.id.listView);
String[] ids = new String[Model.Items.size()];
for (int i= 0; i < ids.length; i++)
{
ids[i] = Integer.toString(i+1);
}
ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids);
listView.setAdapter(adapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
.好的，现在你希望你明白我做了什么，我可以解释这个问题。我想根据我将通过 USB 接收的数据更新列表视图中的全局变量。但是，我似乎无法弄清楚如何做到这一点。我在主活动中尝试了以下代码，但它没有更新数据......
temperature = 5;
adapter.notifyDataSetChanged();
任何帮助将不胜感激。谢谢你的时间。
更新
因此，我创建了一个新的 ArrayList，其中包含要在 ListView 中显示的新数据。然后，我填充列表视图，将列表视图设置为适配器，然后调用 notifyDataSetChanged。但是，我的代码似乎仍然没有更新。非常欢迎任何建议！
public class MainActivity extends Activity
{
public static int temperature;
public static int humidity;
public static int lpg;
public static int alcohol;
ListView listView;
ListView listView1;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Model.LoadModel();
listView = (ListView) findViewById(R.id.listView);
String[] ids = new String[Model.Items.size()];
for (int i= 0; i < ids.length; i++)
{
ids[i] = Integer.toString(i+1);
}
ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids);
listView.setAdapter(adapter);
//Simulate updated data that will come from USB
temperature = 1; humidity = 60; lpg = 5000; alcohol = 500;
//Create new ArrayList with updated data
ArrayList<Item> Items1;
Items1 = new ArrayList<Item>();
Items1.add(new Item(1, "temperature_icon.png", "Temperature/Humidity" + temperature + "°C / " + humidity + "%"));
Items1.add(new Item(2, "gas_icon.png", "LPG" + lpg +" ppm"));
Items1.add(new Item(3, "alcohol_icon.png", "Alcohol" + alcohol + " ppm"));
//Populate ListView
listView1 = (ListView) findViewById(R.id.listView);
String[] ids1 = new String[Items1.size()];
for (int i= 0; i < ids1.length; i++)
{
ids1[i] = Integer.toString(i+1);
}
//Bind new ListView to Adapter
listView1.setAdapter(adapter);
adapter.notifyDataSetChanged();
listView1.invalidateViews();
}
更新#2
现在，我既创建了一个新的列表视图来显示更新的数据，又创建了一个可以将列表视图附加到的新适配器。但是，当我调用通知数据集更改（）;不显示新数据;我仍然看到原始数据。
public class MainActivity extends Activity
{
public static int temperature;
public static int humidity;
public static int lpg;
public static int alcohol;
ListView listView;
ListView listView_new;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Model.LoadModel();
listView = (ListView) findViewById(R.id.listView);
String[] ids = new String[Model.Items.size()];
for (int i= 0; i < ids.length; i++)
{
ids[i] = Integer.toString(i+1);
}
ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids);
listView.setAdapter(adapter);
//--Simulate new data--//
temperature = 1; humidity = 60; lpg = 5000; alcohol = 500;
//Create new ArrayList with updated data
ArrayList<Item> Items_new;
Items_new = new ArrayList<Item>();
Items_new.add(new Item(1, "temperature_icon.png", "Temperature/Humidity " + temperature + "°C / " + humidity + "%"));
Items_new.add(new Item(2, "gas_icon.png", "LPG " + lpg +" ppm"));
Items_new.add(new Item(3, "alcohol_icon.png", "Alcohol " + alcohol + " ppm"));
//Populate ListView
listView_new = (ListView) findViewById(R.id.listView);
String[] ids_new = new String[Items_new.size()];
for (int j= 0; j < ids_new.length; j++)
{
ids_new[j] = Integer.toString(j+1);
}
//Create new adapter
ItemAdapter adapter_new = new ItemAdapter (this,R.layout.row, ids_new);
//Bind new ListView to Adapter
listView_new.setAdapter(adapter_new);
//listView_new.invalidateViews();
adapter_new.notifyDataSetChanged();
}
我认为您的主要活动更新代码不需要那么复杂;我让这个为我工作。它给了我一个包含更新的全局变量值的列表......
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Model.LoadModel();
listView = (ListView) findViewById(R.id.listView);
String[] ids = new String[Model.Items.size()];
for (int i= 0; i < ids.length; i++)
{
ids[i] = Integer.toString(i+1);
}
ItemAdapter adapter = new ItemAdapter(this,R.layout.row, Model.Items);
listView.setAdapter(adapter);
temperature = 1; humidity = 60; lpg = 5000; alcohol = 500;
Model.LoadModel();
ItemAdapter adapter2 = new ItemAdapter(this,R.layout.row, Model.Items);
listView.setAdapter(adapter2);
}
通过适配器将数据从数组馈送到列表视图。要更改列表视图的数据，您需要将新数据设置为适配器，然后在适配器上调用通知数据更改。
像这样：
mAdapter.setListData(mSubMenu1);
mAdapter.notifyDataSetChanged();
更新值后，创建已更新对象的新列表，并使用已更新项的新列表设置新适配器。您必须通过您将创建的"onClick"方法来执行此操作。
更新：
public class MainActivity extends ListActivity {
public static int temperature;
public static int humidity;
public static int lpg;
public static int alcohol;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
temperature = 4;
humidity = 20;
String item1 = "Temperature/Humidity" + temperature + "°C / " + humidity + "%";
List myList = new ArrayList();
myList.add(item1);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myList);
setListAdapter(adapter);
}
public void onClick(View v) {
temperature = 10;
humidity = 30;
String item1 = "Temperature/Humidity" + temperature + "°C / " + humidity + "%";
List myList = new ArrayList();
myList.add(item1);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myList);
setListAdapter(adapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
将以下内容放入垂直方向的线性布局中...
<Button
android:id="@+id/updateList"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Update List"
android:onClick="onClick"/>
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>