我想使用ViewPager
来显示一些加密图像。为此,我创建了PagerAdapter
的扩展名,并将我的解密代码放在instantiateItem
方法中。但问题是解密过程需要太长时间。因此,我在AsyncTask
方法中使用instantiateItem
来显示进度对话框。
现在, ViewPager
首先显示一个空白屏幕,我应该滑动以查看第一张图片。此外 setCurrentItem()
不起作用。
我的代码:
public class FullScreenImageAdapter extends PagerAdapter {
private Activity _activity;
private ArrayList<String> _imagePaths;
private LayoutInflater inflater;
ImageView imgDisplay;
// constructor
public FullScreenImageAdapter(Activity activity,
ArrayList<String> imagePaths) {
this._activity = activity;
this._imagePaths = imagePaths;
}
@Override
public int getCount() {
return this._imagePaths.size();
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == ((RelativeLayout) object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
inflater = (LayoutInflater) _activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View viewLayout = inflater.inflate(R.layout.layout_fullscreen_image, container,
false);
imgDisplay = (ImageView) viewLayout.findViewById(R.id.img_axew);
new DisplayFile().execute(_imagePaths.get(position));
((ViewPager) container).addView(viewLayout);
return viewLayout;
}
private class DisplayFile extends AsyncTask<String, Integer, Integer> {
ProgressDialog progress;
String path;
Bitmap bitmap;
@Override
protected Integer doInBackground(String... arg0) {
path = arg0[0];
File file = new File(path);
try {
bitmap = AxerProcessor.getBitmapFromByte(AxerProcessor.decryptBytes(AxewActivity.password, AxerProcessor.decompressBytes(AxerProcessor.getFileBytes(file))));
} catch (Exception e) {
Toast.makeText(_activity, _activity.getString(R.string.error_wrong_password).replace("%s", file.getName()), Toast.LENGTH_LONG).show();
}
return null;
}
@Override
protected void onPreExecute() {
progress = ProgressDialog.show(_activity, _activity.getString(R.string.alert_decrypt_progress),
_activity.getString(R.string.alert_decrypt_progress_msg), false);
}
@Override
protected void onPostExecute(Integer result) {
progress.dismiss();
imgDisplay.setImageBitmap(bitmap);
}
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((RelativeLayout) object);
}
}
答案 0 :(得分:4)
感谢@ rtsai2000,我最终使用get()
AsyncTask
方法返回真实结果。解决方案是等待结果(viewLayout
)。所以我的代码改为:
public class FullScreenImageAdapter extends PagerAdapter {
private Activity _activity;
private ArrayList<String> _imagePaths;
private LayoutInflater inflater;
ImageView imgDisplay;
View viewLayout;
private ViewGroup container;
// constructor
public FullScreenImageAdapter(Activity activity,
ArrayList<String> imagePaths) {
this._activity = activity;
this._imagePaths = imagePaths;
}
@Override
public int getCount() {
return this._imagePaths.size();
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == ((RelativeLayout) object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
this.container = container;
DisplayFile df = new DisplayFile();
df.execute(_imagePaths.get(position));
View result = null;
try {
result = df.get();
} catch (InterruptedException e) {
} catch (ExecutionException e) {
}
return result;
}
private class DisplayFile extends AsyncTask<String, View, View> {
ProgressDialog progress;
String path;
Bitmap bitmap;
@Override
protected View doInBackground(String... arg0) {
path = arg0[0];
File file = new File(path);
try {
bitmap = AxerProcessor.getBitmapFromByte(AxerProcessor.decryptBytes(AxewActivity.password, AxerProcessor.decompressBytes(AxerProcessor.getFileBytes(file))));
} catch (Exception e) {
Toast.makeText(_activity, _activity.getString(R.string.error_wrong_password).replace("%s", file.getName()), Toast.LENGTH_LONG).show();
}
return viewLayout;
}
@Override
protected void onPreExecute() {
progress = ProgressDialog.show(_activity, _activity.getString(R.string.alert_decrypt_progress),
_activity.getString(R.string.alert_decrypt_progress_msg), false);
inflater = (LayoutInflater) _activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
viewLayout = inflater.inflate(R.layout.layout_fullscreen_image, container,
false);
}
@Override
protected void onPostExecute(View result) {
progress.dismiss();
imgDisplay = (ImageView) result.findViewById(R.id.img_axew);
imgDisplay.setImageBitmap(bitmap);
((ViewPager) container).addView(result);
}
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((RelativeLayout) object);
}
}
答案 1 :(得分:1)
我认为你错过了对PagerAdapter.notifyDataSetChanged()的调用 - http://developer.android.com/reference/android/support/v4/view/PagerAdapter.html#notifyDataSetChanged()
您可以调用notifyDataSetChanged():