前段时间做的新浪微博项目一直想实现listview分页加载数据，今天终于实现了，哈哈！感觉挺好的，今天又写了个demo给大家分享下。

首先说下listview的优化方案，这也是面试中常考的题目。优化方案有三种：1,如果自定义适配器，那么在getView方法中判断contentView是否为空，如果为空创建contentView并返回，如果不为空直接返回contentView。这样能尽可能少创建view。2.给contentView设置tag，传入一个viewHoder对象，用于缓存要实现的数据。3，如果listview中显示的item太多，就要考虑分页加载了。

下面就注意介绍一下分页加载数据。首先在layout下创建listview.xml:

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical" >

android:id="@+id/listView1"

android:layout_width="match_parent"

android:layout_height="wrap_content" >

然后创建listview_item.xml:

android:orientation="vertical"

android:layout_width="fill_parent"

android:layout_height="fill_parent">

android:id="@+id/list_item_text"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:gravity="center"

android:textSize="20sp"

android:paddingTop="10dp"

android:paddingBottom="10dp"/>

再为跟多按钮添加一个xml：

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:gravity="center"

android:orientation="vertical" >

android:id="@+id/loadMoreButton"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:onClick="loadMore"

android:text="加载更多" />

代码部分：

public class ListViewAdapter extends BaseAdapter {

private static Map m=new HashMap();

private List items;

private LayoutInflater inflater;

public ListViewAdapter(List 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 position) {

// TODO Auto-generated method stub

return items.get(position);

}

@Override

public long getItemId(int position) {

// TODO Auto-generated method stub

return position;

}

@Override

public View getView(int position, View contentView, ViewGroup arg2) {

// TODO Auto-generated method stub

contentView=m.get(position);

if(contentView==null){

contentView=inflater.inflate(R.layout.listview_item, null);

TextView text=(TextView) contentView.findViewById(R.id.list_item_text);

text.setText(items.get(position));

}

m.put(position, contentView);

return contentView;

}

public void addItem(String item) {

items.add(item);

}

}

public class ListViewActivity extends Activity implements OnScrollListener {

List items = new ArrayList();

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 ListViewAdapter adapter;

private View loadMoreView;

private Button loadMoreButton;

private Handler handler = new Handler();

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.listview);

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.listView1);

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 view,

int position, long arg3) {

// TODO Auto-generated method stub

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

}

});

}

/**

* 初始化适配器

*/

private void initAdapter() {

for (int i = 0; i < 20; i++) {

items.add(String.valueOf(i + 1));

}

adapter = new ListViewAdapter(items,this);

}

/**

* 滑动时被调用

*/

@Override

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

this.visibleItemCount = visibleItemCount;

visibleLastIndex = firstVisibleItem + visibleItemCount - 1;

}

/**

* 滑动状态改变时被调用

*/

@Override

public void onScrollStateChanged(AbsListView view, int scrollState) {

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 + 20; i++) {

adapter.addItem(String.valueOf(i + 1));

}

}

}

最后看看效果：