ListView Activity，动态插入列表项

Question

我试图动态地将列表项插入到列表视图中。当列表视图被创建并显示在屏幕上时，现在假设我从服务器或某个地方获得了一个项目，现在我想在同一个列表视图中添加此项目。怎么做 ？？有没有什么方法可以在显示的列表视图中动态插入项目，而无需再次创建列表agtain。有什么方法可以改变列表项的状态，这意味着我们可以在显示时进行交互？你的答复将不胜感激。 Thnx提前！

Answer 1

任何你想要添加到正在使用你的Adapter，然后调用notifiyDataSetChanged()您Adapter

与常规ArrayAdapter这将是数据结构（指List）是这样的：

MyAdapter adapter = new MyAdapter(this, R.layout.row, myList); 
listView.setAdapter(adapter); 
... 
//make a bunch of changes to data 
list.add(foo); 
listView.getAdapter().notifyDataSetChanged(); 

我也可以提供一个更复杂的示例，其中包含BaseAdapter。

编辑

我创建了一个小样本，因为这个问题似乎是很常见的。

在我的示例中，我在一个类中做了所有事情，只是为了让它更容易在一个地方跟踪它。

最后，这是一个非常模型 - 视图 - 控制器类型的情况。你甚至可以从这里克隆它运行实际的项目：https://github.com/levinotik/Android-Frequently-Asked-Questions

它的本质是这样的：

/** 
* This Activity answers the frequently asked question 
* of how to change items on the fly in a ListView. 
* 
* In my own project, some of the elements (inner classes, etc) 
* might be extracted into separate classes, but for clarity 
* purposes, I'm doing everything inline. 
* 
* The example here is very, very basic. But if you understand 
* the concept, it can scale to anything. You have complex 
* views bound to complex data wit complex conditions. 
* You could model a facebook user and update the ListView 
* based on changes to that user's data that's represented in 
* your model. 
*/ 
public class DynamicListViewActivity extends Activity { 

    MyCustomAdapter mAdapter; 

    @Override 
    public void onCreate(Bundle state) { 
     super.onCreate(state); 
     ListView listView = new ListView(this); 
     setContentView(listView); 

     /** 
     * Obviously, this will typically some from somewhere else, 
     * as opposed to be creating manually, one by one. 
     */ 

     ArrayList<MyObject> myListOfObjects = new ArrayList<MyObject>(); 

     MyObject object1 = new MyObject("I love Android", "ListViews are cool"); 
     myListOfObjects.add(object1); 
     MyObject object2 = new MyObject("Broccoli is healthy", "Pizza tastes good"); 
     myListOfObjects.add(object2); 
     MyObject object3 = new MyObject("bla bla bla", "random string"); 
     myListOfObjects.add(object3); 

     //Instantiate your custom adapter and hand it your listOfObjects 
     mAdapter = new MyCustomAdapter(this, myListOfObjects); 
     listView.setAdapter(mAdapter); 

     /** 
     * Now you are free to do whatever the hell you want to your ListView. 
     * You can add to the List, change an object in it, whatever. 
     * Just let your Adapter know that that the data has changed so it 
     * can refresh itself and the Views in the ListView. 
     */ 

     /**Here's an example. Set object2's condition to true. 
     If everyting worked right, then the background color 
     of that row will change to blue 
     Obviously you would do this based on some later event. 
     */ 
     object2.setSomeCondition(true); 
     mAdapter.notifyDataSetChanged(); 



    } 


    /** 
    * 
    * An Adapter is bridge between your data 
    * and the views that make up the ListView. 
    * You provide some data and the adapter 
    * helps to place them into the rows 
    * of the ListView. 
    * 
    * Subclassing BaseAdapter gives you the most 
    * flexibility. You'll have to override some 
    * methods to get it working. 
    */ 
    class MyCustomAdapter extends BaseAdapter { 

     private List<MyObject> mObjects; 
     private Context mContext; 

     /** 
     * Create a constructor that takes a List 
     * of some Objects to use as the Adapter's 
     * data 
     */ 
     public MyCustomAdapter(Context context, List<MyObject> objects) { 
      mObjects = objects; 
      mContext = context; 
     } 

     /** 
     * Tell the Adapter how many items are in your data. 
     * Here, we can just return the size of mObjects! 
     */ 
     @Override 
     public int getCount() { 
      return mObjects.size(); 
     } 

     /** 
     * Tell your the Adapter how to get an 
     * item as the specified position in the list. 
     */ 
     @Override 
     public Object getItem(int position) { 
      return mObjects.get(position); 
     } 

     /** 
     * If you want the id of the item 
     * to be something else, do something fancy here. 
     * Rarely any need for that. 
     */ 
     @Override 
     public long getItemId(int position) { 
      return position; 
     } 

     /** 
     * Here's where the real work takes place. 
     * Here you tell the Adapter what View to show 
     * for the rows in the ListView. 
     * 
     * ListViews try to recycle views, so the "convertView" 
     * is provided for you to reuse, but you need to check if 
     * it's null before trying to reuse it. 
     * @param position 
     * @param convertView 
     * @param parent 
     * @return 
     */ 
     @Override 
     public View getView(int position, View convertView, ViewGroup parent) { 
      MyView view; 
      if(convertView == null){ 
       view = new MyView(mContext); 
      } else { 
       view = (MyView) convertView; 
      } 
      /**Here's where we utilize the method we exposed 
      in order to change the view based on the data 
      So right before you return the View for the ListView 
      to use, you just call that method. 
      */ 
      view.configure(mObjects.get(position)); 

      return view; 
     } 
    } 


    /** 
    * Very simple layout to use in the ListView. 
    * Just shows some text in the center of the View 
    */ 
    public class MyView extends RelativeLayout { 

     private TextView someText; 

     public MyView(Context context) { 
      super(context); 

      LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); 
      params.addRule(CENTER_IN_PARENT); 
      someText = new TextView(context); 
      someText.setTextSize(20); 
      someText.setTextColor(Color.BLACK); 
      someText.setLayoutParams(params); 
      addView(someText); 
     } 

     /** 
     * Remember, your View is an regular object like any other. 
     * You can add whatever methods you want and expose it to the world! 
     * We have the method take a "MyObject" and do things to the View 
     * based on it. 
     */ 

     public void configure(MyObject object) { 

      someText.setText(object.bar); 
      //Check if the condition is true, if it is, set background of view to Blue. 
      if(object.isSomeCondition()) { 
       this.setBackgroundColor(Color.BLUE); 
      } else { //You probably need this else, because when views are recycled, it may just use Blue even when the condition isn't true. 
       this.setBackgroundColor(Color.WHITE); 
      } 
     } 
    } 

    /** 
    * This can be anything you want. Usually, 
    * it's some object that makes sense according 
    * to your business logic/domain. 
    * 
    * I'm purposely keeping this class as simple 
    * as possible to demonstrate the point. 
    */ 
    class MyObject { 
     private String foo; 
     private String bar; 
     private boolean someCondition; 


     public boolean isSomeCondition() { 
      return someCondition; 
     } 


     MyObject(String foo, String bar) { 
      this.foo = foo; 
      this.bar = bar; 
     } 

     public void setSomeCondition(boolean b) { 
      someCondition = b; 
     } 
    } 

} 

如果您在此处把握的概念，你应该能够适应（没有双关语意）这ArrayAdapters等

Answer 2

是，通过一个适配器，您在ListView填充，更新项目需要时，增加新项目等

如果你过网拉取数据，你可以首先使用普通的ArrayAdapter（通常通过继承和重写getView()方法来构建您的布局），然后添加和删除它提供的列表中的项目。如果将项目添加到列表中，则向下滚动时会显示在列表的末尾（如果您位于最下面，则立即显示）。如果您修改一个项目，该列表将立即在屏幕上更新。

如果您在模型对象上使用setter，那么适配器将不会知道这一点，但您可以拨打notifyDataSetChanged()。如果您想一次对列表进行多处更改而不会导致屏幕闪烁，您可能还需要查看setNotifyOnChange()方法。

Answer 3

使用notifyDataSetChanged()方法。