Question

我正在尝试创建一个无限的图像列表，每次滚动到底部时都会加载5个项目。首先，我看了Mark Mooibroeks的代码。它基本上是一个日期列表。但是我希望每次向下滚动而不是文本时都会加载图像的效果（因为每日更新，它会从mysql数据库中获取它们的链接）。

package com.pxr.tutorials.neverendinglist;

import java.util.ArrayList;
import java.util.Calendar;

import android.app.ListActivity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ArrayAdapter;


public class NeverEndingList extends ListActivity {

    //how many to load on reaching the bottom
    int itemsPerPage = 5;
    boolean loadingMore = false;




    ArrayList<String> myListItems;
    ArrayAdapter<String> adapter;

    //For test data :-)
    Calendar d = Calendar.getInstance();


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {       
        super.onCreate(savedInstanceState);

        //Remove title bar
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);

        //Remove notification bar
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.listplaceholder);


        //This will hold the new items
        myListItems = new ArrayList<String>();
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myListItems);




        //add the footer before adding the adapter, else the footer will nod load!
        View footerView = ((LayoutInflater)this.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listfooter, null, false);
        this.getListView().addFooterView(footerView);

        //Set the adapter
        this.setListAdapter(adapter);


        //Here is where the magic happens
        this.getListView().setOnScrollListener(new OnScrollListener(){

            //useless here, skip!
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {}

            //dumdumdum         
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {


                //what is the bottom iten that is visible
                int lastInScreen = firstVisibleItem + visibleItemCount;             

                //is the bottom item visible & not loading more already ? Load more !
                if((lastInScreen == totalItemCount) && !(loadingMore)){                 
                    Thread thread =  new Thread(null, loadMoreListItems);
                    thread.start();
                }
            }
        });


        //Load the first 15 items
        Thread thread =  new Thread(null, loadMoreListItems);
        thread.start();

    }


    //Runnable to load the items 
    private Runnable loadMoreListItems = new Runnable() {           
        @Override
        public void run() {
            //Set flag so we cant load new items 2 at the same time
            loadingMore = true;

            //Reset the array that holds the new items
            myListItems = new ArrayList<String>();

            //Simulate a delay, delete this on a production environment!
            try { Thread.sleep(1000);
            } catch (InterruptedException e) {}

            //Get 15 new listitems
            for (int i = 0; i < itemsPerPage; i++) {        

                //Fill the item with some bogus information
                myListItems.add("Date: " + (d.get(Calendar.MONTH)+ 1) + "/" + d.get(Calendar.DATE) + "/" + d.get(Calendar.YEAR) + "http://www.test.com/" + i );             

                // +1 day :-D
                d.add(Calendar.DATE, 1);

            }

            //Done! now continue on the UI thread
            runOnUiThread(returnRes);

        }
    };  


    //Since we cant update our UI from a thread this Runnable takes care of that! 
    private Runnable returnRes = new Runnable() {
        @Override
        public void run() {

            //Loop thru the new items and add them to the adapter
            if(myListItems != null && myListItems.size() > 0){
                for(int i=0;i<myListItems.size();i++)
                    adapter.add(myListItems.get(i));
            }

            //Update the Application title
            setTitle("Neverending List with " + String.valueOf(adapter.getCount()) + " items");

            //Tell to the adapter that changes have been made, this will cause the list to refresh
            adapter.notifyDataSetChanged();

            //Done loading more.
            loadingMore = false;
        }
    };
}

Answer 1

您必须实现自己的自定义适配器，而不是ArrayAdapter<String> adapter。搜索android custom adapter您将找到大量关于它的信息/教程。

无尽的列表中的图像而不是字符串

1 个答案: