Android使用GridView和OnScrollListener
我正在构建一个gridview,其中包含大量的图像,可能大约1000+张图片。为了减少gridview的加载时间,我想使用AbsListView实现一个onScrollListener。我将限制每个视图20个图像,然后当滚动到达底部时,它将加载另外20个图像。这将重复,直到所有图像都已加载 我一直在谷歌上搜索样本,但似乎没有找到一个适合我的代码。有人能告诉我怎么做吗?我目前正在使用imageloader Lazylist处理我的图像。我还使用AsyncTask MainGridView.classAndroid使用GridView和OnScrollListener,android,gridview,android-asynctask,onscroll,Android,Gridview,Android Asynctask,Onscroll,我正在构建一个gridview,其中包含大量的图像,可能大约1000+张图片。为了减少gridview的加载时间,我想使用AbsListView实现一个onScrollListener。我将限制每个视图20个图像,然后当滚动到达底部时,它将加载另外20个图像。这将重复,直到所有图像都已加载 我一直在谷歌上搜索样本,但似乎没有找到一个适合我的代码。有人能告诉我怎么做吗?我目前正在使用imageloader Lazylist处理我的图像。我还使用AsyncTask MainGridView.clas
public class MainGridView extends SherlockActivity {
private ProgressDialog pDialog;
ArrayList<HashMap<String, String>> songsList;
static final String KEY_SONG = "song";
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_ARTIST = "artist";
static final String KEY_CAT_ARTIST = "artistcat";
static final String KEY_DURATION = "duration";
static final String KEY_THUMB_URL = "thumb_url";
static final String KEY_BIG_URL = "big_url";
static final String KEY_CAT_URL = "cat_url";
static String IMAGE_POSITION;
GridView grid;
MainGridViewLazyAdapter adapter;
String cat_url;
String artist_url;
private int visibleThreshold = 5;
private int currentPage = 0;
private int previousTotal = 0;
private boolean loading = true;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gridview_main);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
checkInternetConnection();
grid = (GridView) findViewById(R.id.grid_view);
grid.setOnScrollListener(new OnScrollListener() {
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
if (loading) {
if (visibleItemCount > totalItemCount) {
loading = false;
previousTotal = totalItemCount;
currentPage++;
}
}
if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
// I load the next page of gigs using a background task,
// but you can call any function here.
new loadGridView().execute(currentPage + 1);
loading = true;
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
});
}
public class loadGridView extends AsyncTask<Integer, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainGridView.this);
pDialog.setTitle("Connect to Server");
pDialog.setMessage("This process can take a few seconds to a few minutes, depending on your Internet Connection Speed.");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(Integer... args) {
// updating UI from Background Thread
Intent in = getIntent();
songsList = new ArrayList<HashMap<String, String>>();
cat_url = in.getStringExtra(KEY_CAT_URL);
artist_url = in.getStringExtra(KEY_CAT_ARTIST);
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(cat_url); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
map.put(KEY_DURATION, parser.getValue(e, KEY_DURATION));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
map.put(KEY_BIG_URL, parser.getValue(e, KEY_BIG_URL));
// adding HashList to ArrayList
songsList.add(map);
}
return null;
}
@Override
protected void onPostExecute(String args) {
ActionBar ab = getSupportActionBar();
ab.setTitle(artist_url);
adapter=new MainGridViewLazyAdapter(MainGridView.this, songsList);
grid.setAdapter(adapter);
pDialog.dismiss();
}
}
public类MainGridView扩展了SherlockActivity{
私人对话;
ArrayList songsList;
静态最终字符串键\u SONG=“SONG”;
静态最终字符串键\u ID=“ID”;
静态最终字符串键\u TITLE=“TITLE”;
静态最终字符串键\u ARTIST=“ARTIST”;
静态最终字符串键\u CAT\u ARTIST=“artistcat”;
静态最终字符串键\u DURATION=“DURATION”;
静态最终字符串键\u THUMB\u URL=“THUMB\u URL”;
静态最终字符串键\u BIG\u URL=“BIG\u URL”;
静态最终字符串键\u CAT\u URL=“CAT\u URL”;
静态字符串图像_位置;
网格视图网格;
MainGridViewLazyAdapter适配器;
字符串cat_url;
字符串艺术家(url),;
私有int visibleThreshold=5;
private int currentPage=0;
private int previousTotal=0;
私有布尔加载=真;
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.gridview_main);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
检查InternetConnection();
grid=(GridView)findviewbyd(R.id.grid\u视图);
setOnScrollListener(新的OnScrollListener(){
@凌驾
public void onScroll(AbsListView视图,int firstVisibleItem,
int visibleItemCount,int totalItemCount){
//TODO自动生成的方法存根
如果(装载){
如果(visibleItemCount>totalItemCount){
加载=假;
previousTotal=totalItemCount;
currentPage++;
}
}
如果(!loading&&(totalItemCount-visibleItemCount)值
put(KEY_ID,parser.getValue(e,KEY_ID));
put(KEY_TITLE,parser.getValue(e,KEY_TITLE));
put(KEY_-ARTIST,parser.getValue(e,KEY_-ARTIST));
put(KEY_DURATION,parser.getValue(e,KEY_DURATION));
put(KEY_THUMB_URL,parser.getValue(e,KEY_THUMB_URL));
put(KEY_BIG_URL,parser.getValue(e,KEY_BIG_URL));
//将哈希列表添加到ArrayList
歌曲列表。添加(地图);
}
返回null;
}
@凌驾
受保护的void onPostExecute(字符串参数){
ActionBar ab=getSupportActionBar();
ab.setTitle(艺术家地址);
adapter=新的MainGridViewLazyAdapter(MainGridView.this,songsList);
设置适配器(适配器);
pDialog.disclose();
}
}
我想您希望从URL加载图像。为此,您可以使用以下解决方案:
为了使用onScrollListener
控制分页,我认为您需要查看。这是一个简单的示例,但您唯一需要添加的是检查是否已到达xml的最后一项
在AsyncTask
(每次新加载时调用)中,您只需解析xml中的一点数据(对应于案例中的20项)。这是一个基于代码的使用示例:
public class MainGridView extends SherlockActivity implements OnScrollListener {
public static final String KEY_SONG = "song";
public static final String KEY_ID = "id";
public static final String KEY_TITLE = "title";
public static final String KEY_ARTIST = "artist";
public static final String KEY_CAT_ARTIST = "artistcat";
public static final String KEY_DURATION = "duration";
public static final String KEY_THUMB_URL = "thumb_url";
public static final String KEY_BIG_URL = "big_url";
public static final String KEY_CAT_URL = "cat_url";
private final static int ITEMS_PPAGE = 20;
private ProgressDialog mDialog;
private ArrayList<HashMap<String, String>> mSongsList;
private static String IMAGE_POSITION;
private GridView mGridView;
//MainGridViewLazyAdapter mAdapter;
private ArrayAdapter<String> mAdapter;
private String cat_url;
private String artist_url;
private int mVisibleThreshold = 5;
private int mCurrentPage = 0;
private int mPreviousTotal = 0;
private boolean mLoading = true;
private boolean mLastPage = false;
private String mXml;
@Override
public void onCreate(Bundle savedInstanceState) {
setTheme(SherlockBarUtils.getCurrentTheme(this));
super.onCreate(savedInstanceState);
setContentView(R.layout.gridview_main);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//checkInternetConnection();
mGridView = (GridView) findViewById(R.id.grid_view);
mGridView.setOnScrollListener(this);
mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
//mAdapter=new MainGridViewLazyAdapter(MainGridView.this);
mGridView.setAdapter(mAdapter);
new DownloadDataAsyncTask().execute();
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (mLoading) {
if (totalItemCount > mPreviousTotal) {
mLoading = false;
mPreviousTotal = totalItemCount;
mCurrentPage++;
// Find your own condition in order to know when you
// have finished displaying all items
if (mCurrentPage + 1 > 50) {
mLastPage = true;
}
}
}
if (!mLastPage && !mLoading &&
(totalItemCount - visibleItemCount) <= (firstVisibleItem + mVisibleThreshold)) {
new AddItemsAsyncTask().execute();
mLoading = true;
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
public class DownloadDataAsyncTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
mDialog = new ProgressDialog(MainGridView.this);
mDialog.setTitle("Connect to Server");
mDialog.setMessage("This process can take a few seconds to a few minutes, depending on your Internet Connection Speed.");
mDialog.setIndeterminate(false);
mDialog.setCancelable(false);
mDialog.show();
}
@Override
protected String doInBackground(String... args) {
// Downloading XML
/*
Intent in = getIntent();
mSongsList = new ArrayList<HashMap<String, String>>();
cat_url = in.getStringExtra(KEY_CAT_URL);
artist_url = in.getStringExtra(KEY_CAT_ARTIST);
XMLParser parser = new XMLParser();
mXml = parser.getXmlFromUrl(cat_url); // getting XML from URL
*/
return null;
}
@Override
protected void onPostExecute(String args) {
/*
getSupportActionBar().setTitle(artist_url);
*/
mDialog.dismiss();
mLoading = false;
}
}
public class AddItemsAsyncTask extends AsyncTask<Integer, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(Integer... args) {
MainGridView.this.runOnUiThread(new Runnable() {
@Override
public void run() {
// Parsing 20 more items and adding them to the adapter
for (int i = mCurrentPage * ITEMS_PPAGE; i < (mCurrentPage + 1) * ITEMS_PPAGE; i++) {
MainGridView.this.mAdapter.add(String.valueOf(Math.random() * 5000));
}
MainGridView.this.mAdapter.notifyDataSetChanged();
}
});
return null;
}
@Override
protected void onPostExecute(String args) {
}
}
}
公共类MainGridView扩展SherlockActivity实现OnScrollListener{
公共静态最终字符串键\u SONG=“SONG”;
公共静态最终字符串键\u ID=“ID”;
公共静态最终字符串键\u TITLE=“TITLE”;
公共静态最终字符串键\u ARTIST=“ARTIST”;
公共静态最终字符串键\u CAT\u ARTIST=“artistcat”;
公共静态最终字符串键\u DURATION=“DURATION”;
公共静态最终字符串KEY\u THUMB\u URL=“THUMB\u URL”;
公共静态最终字符串键\u BIG\u URL=“BIG\u URL”;
公共静态最终字符串键\u CAT\u URL=“CAT\u URL”;
私人最终静态整数项目=20;
私人住宅;
私人ArrayList mSongsList;
私有静态字符串图像_位置;
私有网格视图mGridView;
//MainGridViewLazyAdapter mAdapter;
私人ArrayaAdapter mAdapter;
私有字符串cat_url;
私有字符串艺术家的url;
私有int MVisibleThrreshold=5;
private int mCurrentPage=0;
private int mPreviousTotal=0;
私有布尔值mLoading=true;
私有布尔值mLastPage=false;
私有字符串mXml;
@凌驾
创建时的公共void(Bundle savedInstanceState){
setTheme(SherlockBarUtils.getCurrentTheme(this));
super.onCreate(savedInstanceState);
setContentView(R.layout.gridview_main);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//检查InternetConnection();
mGridView=(GridView)findviewbyd(R.id.grid\u视图);
mGridView.setOnScrollListener(此);
mAdapter=newarrayadapter(这是android.R.layout.simple\u list\u item\u 1);
//mAdapter=newmainGridViewLazyAdapter(MainGridView.this);
mGridView.setAdapter(mAdapter);
新建DownloadDataAsyncTask().execute();
}
@凌驾
public void onScroll(AbsListView视图、int firstVisibleItem、int visibleItemCount、int totalItemCount){
如果(最大负载){
如果(totalItemCount>MPPreviousTotal){
mLoading=假;
MPPreviousTotal=totalItemCount;
mCurrentPage++;
//找出你自己的情况,以便知道你什么时候