Android系列之ListView实现分页和类似异步加载效果

在做项目的时候我遇到这样一种业务，就是我需要将联系人已列表的形式展示出来以供选择，当然手机中的联系人肯定不止一条，大多情况很难一屏展示，那么就需要类似分页的效果。这里用ListView去实现。首先上效果图



点击加载后就继续加载后面的12条数据。



这样我们就实现了我们想要的分页效果了。

首先创建一个activity_link.xml作为承载view。代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/kehuan05"
android:orientation="vertical" >

<ListView
android:id="@+id/listview_item"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>

</LinearLayout>

其中就一个ListView比较简单，然后我们再新建一个ListView(我们可以这样去理解)模板 link_listview_item.xml这个页决定了ListView怎样展示，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >

<CheckBox
android:id="@+id/checkBox1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/list_item_text_num"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingRight="15dp"
android:textColor="@color/wite" />

<TextView

android:layout_width="wrap_content"
android:textColor="@color/wite"
android:layout_height="wrap_content"
android:id="@+id/list_item_text_name" />

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/flag" />

</LinearLayout>

从代码中很容易看出，左边一个选择框最右边是图片。请参照上图不难理解。

再添加一个适配器：

package com.egojit.crm;

import java.util.HashMap;
import java.util.List;

import com.egojit.crm.Model.ModelLinkMain;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class AdapterLinkList extends BaseAdapter {

private List<ModelLinkMain> items;
private LayoutInflater inflater;
private static HashMap<Integer,View> m=new HashMap<Integer,View>();

public AdapterLinkList( List<ModelLinkMain> items, Context context) {
super();
this.items = items;
this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return items.size();
}

@Override
public Object getItem(int arg0) {
// TODO Auto-generated method stub
return items.get(arg0);
}

@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return arg0;
}

@Override
public View getView(int position, View contentView, ViewGroup arg2) {
contentView=m.get(position);
if(contentView==null){
contentView=inflater.inflate(R.layout.link_listview_item, null);
TextView text=(TextView) contentView.findViewById(R.id.list_item_text_num);
text.setText(String.valueOf(items.get(position).id)+".");
TextView textName=(TextView) contentView.findViewById(R.id.list_item_text_name);
textName.setText(items.get(position).name);
}
m.put(position, contentView);
return contentView;
}

public void addItem(ModelLinkMain item) {
items.add(item);
}

}

添加一个名字为LinkActivity的Activity。代码如下：

package com.egojit.crm;

import java.util.ArrayList;
import java.util.List;

import com.egojit.crm.Model.ModelLinkMain;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

public class LinkActivity extends Activity implements OnScrollListener{

List<ModelLinkMain> items = new ArrayList<ModelLinkMain>();
private ListView listView;
private int visibleLastIndex = 0;   //最后的可视项索引
private int visibleItemCount;       // 当前窗口可见项总数
private AdapterLinkList adapter;
private View loadMoreView;
private Button loadMoreButton;
private Handler handler = new Handler();

@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
this.setContentView(R.layout.activity_link);

loadMoreView = getLayoutInflater().inflate(R.layout.load_more, null);
loadMoreButton = (Button) loadMoreView.findViewById(R.id.loadMoreButton);
loadMoreButton.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
loadMoreButton.setText("正在加载...");   //设置按钮文字loading
handler.postDelayed(new Runnable() {
@Override
public void run() {
loadData();

adapter.notifyDataSetChanged(); //数据集变化后,通知adapter
listView.setSelection(visibleLastIndex - visibleItemCount + 1); //设置选中项

loadMoreButton.setText("加载更多");    //恢复按钮文字
}
}, 1000);
}
});

listView = (ListView) this.findViewById(R.id.listview_item);

listView.addFooterView(loadMoreView);   //设置列表底部视图
// listView.addHeaderView(v)    //设置列表顶部视图

initAdapter();

listView.setAdapter(adapter);                //自动为id是list的ListView设置适配器

listView.setOnScrollListener(this);     //添加滑动监听
listView.setOnItemClickListener(new OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position,long arg3) {
// TODO Auto-generated method stub

Toast.makeText(getApplicationContext(), items.get(position).name,Toast.LENGTH_SHORT).show();
}
});
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub

this.visibleItemCount = visibleItemCount;
visibleLastIndex = firstVisibleItem + visibleItemCount - 1;

}

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
int itemsLastIndex = adapter.getCount() - 1;    //数据集最后一项的索引
int lastIndex = itemsLastIndex + 1;             //加上底部的loadMoreView项
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE && visibleLastIndex == lastIndex) {
//如果是自动加载,可以在这里放置异步加载数据的代码
Log.i("LOADMORE", "loading...");
}
}

/**
* 模拟加载数据
*/
private void loadData() {
int count = adapter.getCount();
for (int i = count; i < count + 12; i++) {
ModelLinkMain m1=new ModelLinkMain();
m1.id=i+1;
m1.name="gaolu"+i;
adapter.addItem(m1);
}
}

/**
* 初始化适配器
*/
private void initAdapter() {

for (int i = 0; i < 12; i++) {

ModelLinkMain m1=new ModelLinkMain();
m1.id=i+1;
m1.name="gaolu"+i;
items.add(m1);
}
adapter = new AdapterLinkList(items,this);
}

}

其中大家看到一个ModelLinkMain类型，这是我定义的类，有id，name字段。通过这些大家很容易去重现代码。