GridView翻页
GridView翻页(精确监听AbsListView滚动至底部)
本文来自http://blog.****.net/hellogv/ ,引用必须注明出处!
用户使用android客户端时,当ListView滚动至底部,可以由一个按钮来提示用户是否读下一页,那么如果使用GridView呢?现在很多WEB 2.0上的体验就是当底部时自动读取下一页数据,GridView(ListView也可)可以采用这种方法。网上已经有很多文章介绍了如何判断ListView是否滚动至底部,原理是 AbsListView.getLastVisiblePosition() = (AbsListView.getCount() - 1) 即到底,如果往上拖一点,用户看起来已经离开底部,但实际上 AbsListView.getLastVisiblePosition() == (AbsListView.getCount() - 1) 依然成立,会导致误判断。本文在它们基础上加以改进,做到更精确地监听是否滚动至底部。先来看看本文程序运行的效果:
原理是在AbsListView.getLastVisiblePosition() = =(AbsListView.getCount() - 1) 时,保存最后一个Item的绝对坐标,如果两次获取的绝对Y值都一样,即到底然后执行回调函数......源码如下:
import android.view.View;
import android.widget.AbsListView;
import android.widget.Toast;
import android.widget.AbsListView.OnScrollListener;
/**
* 滚动至列表底部,读取下一页数据
*/
public class AutoLoadListener implements OnScrollListener {
public interface AutoLoadCallBack {
void execute();
}
private int getLastVisiblePosition = 0, lastVisiblePositionY = 0;
private AutoLoadCallBack mCallback;
public AutoLoadListener(AutoLoadCallBack callback) {
this.mCallback = callback;
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
//滚动到底部
if (view.getLastVisiblePosition() == (view.getCount() - 1)) {
View v = (View) view.getChildAt(view.getChildCount() - 1);
int[] location = new int[2];
v.getLocationOnScreen(location); //获取在整个屏幕内的绝对坐标
int y = location[1];
MyLog.d( "x" + location[0], "y" + location[1]);
if (view.getLastVisiblePosition() != getLastVisiblePosition && lastVisiblePositionY != y) //第一次拖至底部
{
Toast.makeText(view.getContext(), "已经拖动至底部,再次拖动即可翻页", 500).show();
getLastVisiblePosition = view.getLastVisiblePosition();
lastVisiblePositionY = y;
return;
} else if (view.getLastVisiblePosition() == getLastVisiblePosition && lastVisiblePositionY == y) //第二次拖至底部
{
mCallback.execute();
}
}
//未滚动到底部,第二次拖至底部都初始化
getLastVisiblePosition = 0;
lastVisiblePositionY = 0;
}
}
public void onScroll(AbsListView arg0, int arg1, int arg2, int arg3) {
}
}
import android.widget.AbsListView;
import android.widget.Toast;
import android.widget.AbsListView.OnScrollListener;
/**
* 滚动至列表底部,读取下一页数据
*/
public class AutoLoadListener implements OnScrollListener {
public interface AutoLoadCallBack {
void execute();
}
private int getLastVisiblePosition = 0, lastVisiblePositionY = 0;
private AutoLoadCallBack mCallback;
public AutoLoadListener(AutoLoadCallBack callback) {
this.mCallback = callback;
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
//滚动到底部
if (view.getLastVisiblePosition() == (view.getCount() - 1)) {
View v = (View) view.getChildAt(view.getChildCount() - 1);
int[] location = new int[2];
v.getLocationOnScreen(location); //获取在整个屏幕内的绝对坐标
int y = location[1];
MyLog.d( "x" + location[0], "y" + location[1]);
if (view.getLastVisiblePosition() != getLastVisiblePosition && lastVisiblePositionY != y) //第一次拖至底部
{
Toast.makeText(view.getContext(), "已经拖动至底部,再次拖动即可翻页", 500).show();
getLastVisiblePosition = view.getLastVisiblePosition();
lastVisiblePositionY = y;
return;
} else if (view.getLastVisiblePosition() == getLastVisiblePosition && lastVisiblePositionY == y) //第二次拖至底部
{
mCallback.execute();
}
}
//未滚动到底部,第二次拖至底部都初始化
getLastVisiblePosition = 0;
lastVisiblePositionY = 0;
}
}
public void onScroll(AbsListView arg0, int arg1, int arg2, int arg3) {
}
}
主程序为testScroll.java,源码如下:
public class testScroll extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setTitle( "精确监听AbsListView滚动至底部----hellogv");
GridView gridview = (GridView) findViewById(R.id.gridview);
// 生成动态数组,并且转入数据
ArrayList<HashMap<String, Object>> lstImageItem = new ArrayList<HashMap<String, Object>>();
for ( int i = 0; i < 30; i++) {
HashMap<String, Object> map = new HashMap<String, Object>();
map.put( "ItemImage", R.drawable.icon); // 添加图像资源的ID
map.put( "ItemText", "NO." + String.valueOf(i)); // 按序号做ItemText
lstImageItem.add(map);
}
// 生成适配器的ImageItem <====> 动态数组的元素,两者一一对应
SimpleAdapter saImageItems = new SimpleAdapter( this, // 没什么解释
lstImageItem, // 数据来源
R.layout.night_item, // night_item的XML实现
// 动态数组与ImageItem对应的子项
new String[] { "ItemImage", "ItemText" },
// ImageItem的XML文件里面的一个ImageView,两个TextView ID
new int[] { R.id.ItemImage, R.id.ItemText });
//添加自动读页的事件
AutoLoadListener autoLoadListener = new AutoLoadListener(callBack);
gridview.setOnScrollListener(autoLoadListener);
// 添加并且显示
gridview.setAdapter(saImageItems);
// 添加消息处理
gridview.setOnItemClickListener( new ItemClickListener());
}
AutoLoadCallBack callBack= new AutoLoadCallBack(){
public void execute() {
Toast.makeText(testScroll. this, "滚动至底部", 500).show();
}
};
// 当AdapterView被单击(触摸屏或者键盘),则返回的Item单击事件
class ItemClickListener implements OnItemClickListener {
public void onItemClick(AdapterView<?> arg0, // The AdapterView where the
// click happened
View arg1, // The view within the AdapterView that was clicked
int arg2, // The position of the view in the adapter
long arg3 // The row id of the item that was clicked
) {
// 在本例中arg2=arg3
HashMap<String, Object> item = (HashMap<String, Object>) arg0
.getItemAtPosition(arg2);
// 显示所选Item的ItemText
setTitle((String) item.get( "ItemText"));
}
转载于:https://my.oschina.net/janson2013/blog/178061