我在我的应用程序中使用延迟加载，我想显示加载动画或进度条或任何内容，直到内容从远程服务器加载，只是告诉用户该页面不是空白或正在构建中。这是我的活动，请告诉我让用户等到内容加载的解决方案。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.hotel_listview);
// URL to the XML data
String strUrl = "http://xxx.php";
// Creating a new non-ui thread task to download xml data
DownloadTask downloadTask = new DownloadTask();
// Starting the download process
downloadTask.execute(strUrl);
if (!isOnline(this)) {
showDialog(DIALOG_ERROR_CONNECTION); //displaying the created dialog.
} else {
//Internet available. Do what's required when internet is available.
}
}
public boolean isOnline(Context c) {
ConnectivityManager cm = (ConnectivityManager) c
.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo ni = cm.getActiveNetworkInfo();
if (ni != null && ni.isConnected())
return true;
else
return false;
}
@Override
protected Dialog onCreateDialog(int id) {
Dialog dialog = null;
switch (id) {
case DIALOG_ERROR_CONNECTION:
AlertDialog.Builder errorDialog = new AlertDialog.Builder(this);
errorDialog.setTitle("Error");
errorDialog.setMessage("Connection Error....!");
errorDialog.setNeutralButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
}
});
AlertDialog errorAlert = errorDialog.create();
return errorAlert;
default:
break;
}
return dialog;
}
/** A method to download xml data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
}
return data;
}
/** AsyncTask to download xml data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
@Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
if (result != null) {
// The parsing of xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}}
}
/** AsyncTask to parse xml data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
StringReader reader;
// Doing the parsing of xml data in a non-ui thread
@Override
protected SimpleAdapter doInBackground(String... strXml) {
try{
reader = new StringReader(strXml[0]);
}catch(Exception e){
Log.d("XML Exception1",e.toString());
}
// Instantiating xml parser class
HotelListParser hotelListParser = new HotelListParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> hotelList = null;
try{
// Getting the parsed data as a List construct
hotelList = hotelListParser.parse(reader);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "hotel","photo","rupees","review","distance"};
// Ids of views in listview_layout
int[] to = { R.id.tv_hotelName,R.id.iv_photo,R.id.tv_rupees,R.id.tv_review,R.id.tv_distance};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), hotelList, R.layout.hotel_listview_layout, from, to);
return adapter;
}
/** Invoked by the Android when "doInBackground" is executed */
@Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
mListView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("photo_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("photo_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("photo_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("photo",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
if (result != null) {
// Getting the path to the downloaded image
String path = (String) result.get("photo");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) mListView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("photo",path);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
}}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
} `
答案 0 :(得分：0)
显示和隐藏的进度对话框方法。 或您可以在onPreExecute（）中编写代码以显示onPostExecute（）以隐藏进度对话框。
ProgressDialog barProgressDialog;
public void showHideProgressDialog(boolean status){
if(barProgressDialog==null){
barProgressDialog = new ProgressDialog(YourActivity.this);
barProgressDialog.setTitle("Title");
barProgressDialog.setMessage("Your Message");
}
if(status){
barProgressDialog.show();
}else{
barProgressDialog.dismiss();
}
}
AsyncTask方法。
public void onPreExecute(...){
showHideProgressDialog(true)
..
}
public void onPostExecute(...){
showHideProgressDialog(false)
...
}
建议：仅在设备具有数据连接时执行http内容
.....
DownloadTask downloadTask = new DownloadTask();
// dont call http stuff here
//downloadTask.execute(strUrl);
if (!isOnline(this)) {
showDialog(DIALOG_ERROR_CONNECTION); //displaying the created dialog.
} else {
//Internet available. Do what's required when internet is available.
downloadTask.execute(strUrl);
}
....