我正在尝试在以下代码中添加“加载”对话框以从服务器获取图像并将其显示在“图库”视图中。它显示空白屏幕，直到图像来。请帮助我如何在从服务器获取图像时显示“加载”对话框。
这是代码，请帮助。
public class ImagedisplaytestActivity extends Activity {
private ImageView leftArrowImageView;
private ImageView rightArrowImageView;
private Gallery gallery;
public int selectedImagePosition;
private GalleryImageAdapter galImageAdapter;
private String bitmapImg = "";
Bitmap bitmap = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setupUI();
}
private void setupUI() {
Intent i = getIntent();
Bundle extras=i.getExtras();
bitmapImg = extras.getString("BitmapImage");
selectedImagePosition = extras.getInt("Pos");
leftArrowImageView = (ImageView) findViewById(R.id.left_arrow_imageview);
rightArrowImageView = (ImageView) findViewById(R.id.right_arrow_imageview);
gallery = (Gallery) findViewById(R.id.gallery);
leftArrowImageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (selectedImagePosition > 0) {
--selectedImagePosition;
}
gallery.setSelection(selectedImagePosition, false);
}
});
rightArrowImageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (selectedImagePosition < DetailView.bitmapURL.size() - 1) {
++selectedImagePosition;
}
gallery.setSelection(selectedImagePosition, false);
}
});
gallery.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
selectedImagePosition = pos;
if (selectedImagePosition > 0 && selectedImagePosition < DetailView.bitmapURL.size() - 1) {
leftArrowImageView.setImageDrawable(getResources().getDrawable(R.drawable.arrow_left_disabled));
rightArrowImageView.setImageDrawable(getResources().getDrawable(R.drawable.arrow_right_disabled));
} else if (selectedImagePosition == 0) {
leftArrowImageView.setImageDrawable(getResources().getDrawable(R.drawable.arrow_left_enabled));
} else if (selectedImagePosition == DetailView.bitmapURL.size() - 1) {
rightArrowImageView.setImageDrawable(getResources().getDrawable(R.drawable.arrow_right_enabled));
}
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
}
});
galImageAdapter = new GalleryImageAdapter(this, DetailView.bitmapURL);
gallery.setAdapter(galImageAdapter);
if (DetailView.bitmapURL.size() > 0) {
gallery.setSelection(selectedImagePosition, false);
}
if (DetailView.bitmapURL.size() == 1) {
rightArrowImageView.setImageDrawable(getResources().getDrawable(R.drawable.arrow_right_disabled));
}
}
public class GalleryImageAdapter extends BaseAdapter {
private Activity context;
private ImageView imageView;
private List<String> plotsImages;
private ViewHolder holder;
public GalleryImageAdapter(Activity context, List<String> plotsImages) {
this.context = context;
this.plotsImages = plotsImages;
}
@Override
public int getCount() {
return plotsImages.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
holder = new ViewHolder();
imageView = new ImageView(this.context);
imageView.setPadding(3, 3, 3, 3);
convertView = imageView;
holder.imageView = imageView;
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.imageView.setLayoutParams(new Gallery.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
holder.imageView.setScaleType(ImageView.ScaleType.FIT_XY);
try {
bitmap = DownloadImage(plotsImages.get(position));
holder.imageView.setImageBitmap(bitmap);
bitmap = null;
} catch (Exception e) {
e.printStackTrace();
}
return imageView;
}
private class ViewHolder {
ImageView imageView;
}
private Bitmap DownloadImage(String URL){
Bitmap bitmap = null;
try {
InputStream in = OpenHttpConnection(URL);
bitmap = BitmapFactory.decodeStream(in);
in.close();
} catch (IOException e1) {
e1.printStackTrace();
}
return bitmap;
}
private InputStream OpenHttpConnection(String urlString) throws IOException{
InputStream in = null;
int response = -1;
URL url = new URL(urlString);
URLConnection conn = url.openConnection();
if (!(conn instanceof HttpURLConnection)) {
throw new IOException("Not an HTTP connection");
}
try{
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
if (response == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
}
}
catch (Exception ex){
throw new IOException("Error connecting");
}
return in;
}
}
@Override
public void onBackPressed() {
DetailView.bundleID = DetailView.idList.get(selectedImagePosition);
super.onBackPressed();
}
}
答案 0 :(得分：0)
使用assynctask，
在那个assynctask方法中，您可以在doinbackground()中编写从服务器获取图像，
在此期间，您可以使用preexectue()显示提醒对话框，从服务器加载后只需关闭postexectue()中的提醒对话框。
答案 1 :(得分：0)
此代码适用于我
private class LoadGlobalDataSearch extends AsyncTask<String, Void, Void>
{
@Override
protected void onPostExecute(Void result)
{
super.onPostExecute(result);
progressdialog.dismiss();
}
@Override
protected Void doInBackground(String... params)
{
//Load your images this task
setupUI();
return null;
}
@Override
protected void onPreExecute()
{
super.onPreExecute();
progressdialog = ProgressDialog.show(MainActivity.this, "",getString(R.string.inprogress));
}
}
在你的oncreate方法中调用这个类
new loadImages().execute(0);
答案 2 :(得分：0)
您可以使用进度拨号直到下载图像，然后删除对话框。
在OpenHttpConnection中添加 -
dialog = ProgressDialog.show(DutyRotaActivity.this, "",
"Please wait for few seconds...", true);
关闭对话框。
dialog.dismiss();
或者您也可以使用异步任务。因为网络操作应该总是在其他线程上进行
不在主线程中。在preExecute的情况下，添加对话框并在postExecute中关闭对话框。并在doinbackground中调用您的downloadimage函数，该函数也会执行这些操作。
这是一个完整的源代码和一个库，可以在listView中懒惰地加载图像。我认为它也可以帮助您解决问题。谢谢
答案 3 :(得分：0)
你应该使用AsyncTask！ 见this also！ ＆安培;在Vogella Example中将清除您的怀疑。 看到这个懒人图片加载DEMO！在github上。