我们都知道网络取数据是耗时操作，如果我们一次性请求所有数据，假如数据量不多那还可以接受，但是如果数据量特别多，那么带来的后果就是用户的愤怒（用户是很没有耐心的），所以这时候我们就需要动态的加载数据，分批加载我们所需的数据，提升用户体验，先上图。
一般如果一个Activity集成越多的功能，代码量也会随之增多，看起来让人烦，我们可以考虑自定义控件将一些操作集成进去。
自定义ListView
1 package com.example.listviewdynamicloading;
2
3 import android.content.Context;
4 import android.util.AttributeSet;
5 import android.view.LayoutInflater;
6 import android.view.View;
7 import android.widget.AbsListView;
8 import android.widget.AbsListView.OnScrollListener;
9 import android.widget.ListView;
10
11 public class ZdyListView extends ListView implements OnScrollListener {
12 private int totalItemCount;// 总数量；
13 private int lastVisibleItem;// 最后一个可见的item；
14 private boolean isLoading;
15 private View footer;
16 private LayoutInflater inflater;
17 public RefleshDatas refleshDatas;
18
19 public ZdyListView(Context context) {
20 super(context);
21 initView(context);
22 }
23
24 public ZdyListView(Context context, AttributeSet attrs) {
25 super(context, attrs);
26 initView(context);
27 }
28
29 public ZdyListView(Context context, AttributeSet attrs, int defStyle) {
30 super(context, attrs, defStyle);
31 initView(context);
32 }
33
34 private void initView(Context context) {
35 footer=inflater.from(context).inflate(R.layout.layout_util_footer, null);
36 this.setOnScrollListener(this);
37 this.addFooterView(footer);
38 this.removeFooterView(footer);
39 }
40
41 @Override
42 public void onScroll(AbsListView view, int firstVisibleItem,
43 int visibleItemCount, int totalItemCount) {
44 this.lastVisibleItem = firstVisibleItem + visibleItemCount;
45 this.totalItemCount = totalItemCount;
46 }
47
48 @Override
49 public void onScrollStateChanged(AbsListView view, int scrollState) {
50 //listview item总数量等于最后一个可见的item并且ListView停下不动了
51 if (totalItemCount == lastVisibleItem&& scrollState == SCROLL_STATE_IDLE) {
52 if (!isLoading) {
53 isLoading = true;
54 this.addFooterView(footer);
55 if (refleshDatas != null) {
56 //回调执行向服务器端请求数据
57 refleshDatas.onLoading();
58 }
59 }
60 }
61 };
62 public void loadComplete() {
63 isLoading = false;
64 this.removeFooterView(footer);//加载完毕，移除footView；
65 }
66 public void setInterface(RefleshDatas refleshDatas) {
67 this.refleshDatas = refleshDatas;
68 }
69 public interface RefleshDatas{
70 public void onLoading();
71 }
72 }
MainActivity
1 package com.example.listviewdynamicloading;
2
3 import java.util.ArrayList;
4
5 import com.example.listviewdynamicloading.ZdyListView.RefleshDatas;
6
7 import android.app.Activity;
8 import android.os.Bundle;
9 import android.os.Handler;
10 import android.os.Message;
11 import android.view.Menu;
12 import android.view.MenuItem;
13 import android.widget.ListView;
14 import android.widget.Toast;
15
16 public class MainActivity extends Activity{
17 //一次从服务器端请求十条数据
18 private int current=1;
19 private int number=9;
20
21
22 private ZdyListView listView; //自定义ListView，将footview，滑动监听等集合在一起，免得Activity代码过多
23 private ArrayList<String> listDatas;
24 private ListViewAdapter adapter;
25
26
27 private Handler handler=new Handler(){
28 public void handleMessage(android.os.Message msg) {
29 switch (msg.what) {
30 case 0x123:
31 setlistView((ArrayList<String>)msg.obj,"firstLoading");//firstLoading标志位代表数据是初次加载的
32 break;
33 case 0x234:
34 setlistView((ArrayList<String>)msg.obj,"addLoading");//addLoading标志位代表数据是初次加载之后请求服务器所得
35 break;
36 case 0x345:
37 showMsg((String)msg.obj);
38 break;
39 default:
40 break;
41 }
42 };
43 };
44
45 @Override
46 protected void onCreate(Bundle savedInstanceState) {
47 super.onCreate(savedInstanceState);
48 setContentView(R.layout.activity_main);
49 listDatas=new ArrayList<String>();
50 listView=(ZdyListView) this.findViewById(R.id.listview);
51 listView.setInterface(new RefleshDatas() {
52 @Override
53 public void onLoading() {
54 getDataThread(current, current+number, "addLoading");
55 }
56 });
57 }
58
59
60
61 @Override
62 protected void onStart() {
63 super.onStart();
64 getDataThread(current,number,"firstLoading");
65 }
66
67 //.........................模拟开启线程向服务器请求数据.....................................
68 private void getDataThread(final int current, final int number,final String type) {
69 final Message msg=new Message();
70 new Thread(){
71 public void run() {
72 ArrayList<String> datas=ListViewDatas.returnNum(current, current+number);
73 if(datas!=null&&datas.size()>0){
74 switch (type) {
75 case "firstLoading":
76 msg.what=0x123;
77 break;
78 case "addLoading":
79 msg.what=0x234;
80 break;
81 default:
82 break;
83 }
84 msg.obj=datas;
85 }else {
86 msg.what=0x345;
87 msg.obj=datas;
88 }
89 handler.sendMessage(msg);
90 };
91 }.start();
92 }
93
94
95
96 private void setlistView(ArrayList<String> datas,String type) {
97 listDatas.addAll(datas);
98 if(type.equals("firstLoading")){//初次加载
99 adapter=new ListViewAdapter(MainActivity.this, listDatas);
100 current=adapter.getCount()+1;
101 listView.setAdapter(adapter);
102 listView.loadComplete();
103 }else if(type.equals("addLoading")){//初次加载后请求的数据，执行notifyDataSetChanged();
104 adapter.notifyDataSetChanged();
105 current=adapter.getCount()+1;
106 listView.loadComplete();
107 }
108 }
109
110
111 protected void showMsg(String str) {
112 Toast.makeText(MainActivity.this, "已加载完毕", Toast.LENGTH_SHORT).show();
113 listView.loadComplete();
114 }
115
116
117
118 }
模拟服务器端数据
1 package com.example.listviewdynamicloading;
2
3 import java.util.ArrayList;
4
5 public class ListViewDatas {
6 //模拟服务器端数据库中的数据，假设现在只有3条数据
7 public static int NUM=53;
8 public static ArrayList<String> returnNum(int startNum,int endNum){
9 ArrayList<String> list=new ArrayList<String>();
10 if(endNum<=NUM){//客户端请求的数据在数据库数据范围之内
11 for(int i=startNum;i<=endNum;i++){
12 list.add(String.valueOf(i));
13 }
14 return list;
15 }else if(endNum>=NUM&&startNum<=NUM){//客户端请求的数据不全在数据库数据范围之内
16 for(int i=startNum;i<=NUM;i++){
17 list.add(String.valueOf(i));
18 }
19 return list;
20 }else if(startNum>NUM){//客户端请求的数据超出数据库数据范围之内
21 return null;
22 }
23 return null;
24 }
25 }
ListView适配器
1 package com.example.listviewdynamicloading;
2
3 import java.util.ArrayList;
4
5 import android.content.Context;
6 import android.view.LayoutInflater;
7 import android.view.View;
8 import android.view.ViewGroup;
9 import android.widget.BaseAdapter;
10 import android.widget.TextView;
11
12 public class ListViewAdapter extends BaseAdapter{
13 private Context context;
14 private ArrayList<String> datas;
15
16 public ListViewAdapter(Context context,ArrayList<String> datas){
17 this.context=context;
18 this.datas=datas;
19 }
20
21 @Override
22 public int getCount() {
23 return datas.size();
24 }
25
26 @Override
27 public Object getItem(int position) {
28 return null;
29 }
30
31 @Override
32 public long getItemId(int position) {
33 return position;
34 }
35
36 @Override
37 public View getView(int position, View convertView, ViewGroup parent) {
38 ViewHolder vh=null;
39 if(convertView==null){
40 vh=new ViewHolder();
41 convertView=LayoutInflater.from(context).inflate(R.layout.listview_item, null);
42 vh.tv=(TextView) convertView.findViewById(R.id.tv);
43 convertView.setTag(vh);
44 }else {
45 vh=(ViewHolder) convertView.getTag();
46 }
47 vh.tv.setText("这是第"+datas.get(position)+"条数据");
48 return convertView;
49 }
50
51
52
53 class ViewHolder{
54 TextView tv;
55 }
56
57
58 }
时间： 2024-12-24 03:44:44