作者comteken ([CR])
看板AndroidDev
标题[问题] progressBar+asyncTask(null reference)
时间Fri Jul 25 03:00:59 2014
public class MorePhotoDialog extends DialogFragment {
private static final String TAG = "MorePhotoDialog";
private CustomAdapter _customAdapter;
private Context _context;
private ListView _listView;
private LinearLayout _linearLayout;
private ProgressBar _progressBar;
public MorePhotoDialog(Context context) {
Log.d(TAG, "new MorePhotoDialog");
_customAdapter = new CustomAdapter(context);
_context = context;
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.custom_adapter, null);
_progressBar = (ProgressBar) view
.findViewById(R.id.custom_adapter_progressBar2);
_linearLayout = (LinearLayout) view
.findViewById(R.id.custom_adapter_progressLine);
_listView = (ListView) view.findViewById(R.id.custom_adapter_listView);
_listView.setAdapter(_customAdapter);
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setView(view);
builder.setTitle(R.string.more_photo_dialog_more);
return builder.create();
}
int endFlag = 0;
public void addImageLoaderTask(String... urls) {
endFlag = urls.length - 1;
for (int i = 0; i < urls.length - 1; i++) {
ImageLoaderTask imageLoaderTask = new ImageLoaderTask(i);
Log.d(TAG, "imageLoaderTask.execute: " + urls[i]);
imageLoaderTask.execute(urls[i]);
}
}
// private class ImageLoaderTask extends AsyncTask<String, Void,
Bitmap[]> {
private class ImageLoaderTask extends AsyncTask<String, Void, Void> {
private int _flag = 0;
private ProgressBar progressBar;
public ImageLoaderTask(int flag) {
_flag = flag;
// progressBar = (ProgressBar)
getActivity().findViewById(R.id.custom_adapter_progressBar2);
}
@Override
protected void onPreExecute() {
// TODO progress bar
// Display progress bar
if (_flag == 0) {
_linearLayout.setVisibility(View.VISIBLE);
// progressBar.setVisibility(View.VISIBLE);
}
}
@Override
protected Void doInBackground(String... url) {
String imgUrl = url[0];
Log.w(TAG, "url[0] = " + url[0]);
// Getting Caching directory
File cacheDirectory = _context.getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath(),
FunctionUtility.getLastString(imgUrl));
Log.d(TAG, "imgUrl(" + tmpFile.getName() + ") = " + imgUrl);
if (!tmpFile.exists()) {
Log.w(TAG, tmpFile.getPath() + " not exists");
BitmapFuntions.downloadBitmapFromUrl(imgUrl, tmpFile);
}
// Load bitmap and put in adapter
Bitmap bitmap = BitmapFuntions.decodeFile(tmpFile, 300, 200);
_customAdapter.addBitmap(bitmap);
// Show Logs
Log.d(TAG, "bitmap.getByteCount() = " + bitmap.getByteCount());
Log.d(TAG, tmpFile.getPath());
Log.d(TAG, tmpFile.getName() + " = " + tmpFile.length() / 1024
+ " Kb");
return null;
}
@Override
// protected void onPostExecute(Bitmap[] result) {
protected void onPostExecute(Void result) {
Log.d(TAG, "onPostExecute");
_customAdapter.notifyDataSetChanged();
if (_flag == endFlag) {
_linearLayout.setVisibility(View.GONE);
//progressBar.setVisibility(View.GONE);
}
}
}
}
呼叫dialogFragment的方法是
// Show MorePhotoDialog
MorePhotoDialog morePhotoDialog = new MorePhotoDialog(
Image_enlarge.this);
morePhotoDialog
.show(getSupportFragmentManager(), "morePhotoDialog");
morePhotoDialog.addImageLoaderTask(imglist);
可是会跑出NullPointerException
07-24 14:59:22.000: E/AndroidRuntime(7064): java.lang.NullPointerException:
Attempt to invoke virtual method 'void android.view.View.setVisibility(int)'
on a null object reference
07-24 14:59:22.000: E/AndroidRuntime(7064): at
com.gundam.cool.dialog.MorePhotoDialog$ImageLoaderTask.onPreExecute(MorePhotoDialog.java:96)
07-24 14:59:22.000: E/AndroidRuntime(7064): at
android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
07-24 14:59:22.000: E/AndroidRuntime(7064): at
android.os.AsyncTask.execute(AsyncTask.java:535)
不懂为什麽抓不到view...
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1F：推 markzog21:你把要显示的view丢到asyncTask里面去试试看 07/25 16:53
2F：→ markzog21:要显示dialog的view 07/25 16:53
试过了，也是一样的结果
3F：→ corrupt003:你的activity的layout里有view叫 07/25 20:07
4F：→ corrupt003:R.id.custom_adapter_progressBar2 吗？ 07/25 20:07
有，我是用alt+/找到的
※ 编辑: comteken (140.124.249.8), 07/26/2014 09:25:59
5F：推 corrupt003:alt + / 是找到R.java的所有资料…你还是要看activity 07/26 09:30
6F：→ corrupt003: 的layout 有没有订义这个id，因为你是用getActivity去 07/26 09:30
7F：→ corrupt003:取得view的 07/26 09:30
8F：推 freesamael:morePhotoDialog.show() 是 non-blocking call, 07/29 19:48
9F：→ freesamael:FragmentManager 会排程到下一次 main thread 空闲时 07/29 19:48
10F：→ freesamael:才把 DialogFragment 加到 activity。因此 07/29 19:49
11F：→ freesamael:onCreateDialog() 被呼叫的时间会在 07/29 19:49
12F：→ freesamael:addImageLoaderTask() 之後，此时 layout 还没设定 07/29 19:50