android中listview分页加载数据

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<span style="font-family: Arial; background-color: rgb(255, 255, 255);">listview的优化方案，优化方案有三种：</span>

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:

<?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="vertical" >    <ListView        android:id="@+id/listView1"        android:layout_width="match_parent"        android:layout_height="wrap_content" >    </ListView></LinearLayout>

然后创建listview_item.xml:

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

再为跟多按钮添加一个xml：

<?xml version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:gravity="center"      android:orientation="vertical" >        <Button          android:id="@+id/loadMoreButton"          android:layout_width="fill_parent"          android:layout_height="wrap_content"          android:onClick="loadMore"          android:text="加载更多" />    </LinearLayout>

代码部分：

public class ListViewAdapter extends BaseAdapter {        private static Map<Integer,View> m=new HashMap<Integer,View>();            private List<String> items;      private LayoutInflater inflater;            public ListViewAdapter(List<String> 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<String> items = new ArrayList<String>();         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：

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