当我单击下载按钮时，我有listview.in 行项目progressbar，2 按钮和一个图像视图，然后下载过程开始，但是当我向下滚动时应用程序崩溃以及当我向下滚动时如何listview在行项目中保存状态？我的代码如下:: ：
public class TestHopeDownload extends Activity {
private ListView lstView;
private ImageAdapter imageAdapter;
private Handler handler = new Handler();
ArrayList<Url_Dto> list = new ArrayList<Url_Dto>();
File download;
public static final int DIALOG_DOWNLOAD_THUMBNAIL_PROGRESS = 0;
String strDownloaDuRL;
ArrayList<HashMap<String, Object>> MyArrList = new ArrayList<HashMap<String, Object>>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test_hope_download);
new LoadContentFromServer().execute();
}
public void ShowThumbnailData() {
// ListView and imageAdapter
lstView = (ListView) findViewById(R.id.listView1);
lstView.setClipToPadding(false);
list = DBAdpter.getUrl_Detail();
imageAdapter = new ImageAdapter(getApplicationContext());
lstView.setAdapter(imageAdapter);
}
public void startDownload(final int position) {
Runnable runnable = new Runnable() {
int Status = 0;
public void run() {
// String urlDownload = list.get(position).url_video;
String urlDownload = MyArrList.get(position)
.get("VideoPathThum").toString();
Log.v("log_tag", "urlDownload ::: " + urlDownload);
int count = 0;
try {
URL url = new URL(urlDownload);
URLConnection conexion = url.openConnection();
conexion.connect();
int lenghtOfFile = conexion.getContentLength();
Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);
InputStream input = new BufferedInputStream(
url.openStream());
// Get File Name from URL
String fileName = urlDownload.substring(
urlDownload.lastIndexOf('/') + 1,
urlDownload.length());
download = new File(
Environment.getExternalStorageDirectory()
+ "/download/");
if (!download.exists()) {
download.mkdir();
}
strDownloaDuRL = download + "/" + fileName;
OutputStream output = new FileOutputStream(strDownloaDuRL);
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
Status = (int) ((total * 100) / lenghtOfFile);
output.write(data, 0, count);
// Update ProgressBar
handler.post(new Runnable() {
public void run() {
updateStatus(position, Status);
}
});
}
output.flush();
output.close();
input.close();
} catch (Exception e) {
}
}
};
new Thread(runnable).start();
}
private void updateStatus(int index, int Status) {
View v = lstView.getChildAt(index - lstView.getFirstVisiblePosition());
// Update ProgressBar
ProgressBar progress = (ProgressBar) v.findViewById(R.id.progressBar);
progress.setProgress(Status);
// Update Text to ColStatus
TextView txtStatus = (TextView) v.findViewById(R.id.ColStatus);
txtStatus.setPadding(10, 0, 0, 0);
txtStatus.setText("Load : " + String.valueOf(Status) + "%");
// Enabled Button View
if (Status >= 100) {
Button btnView = (Button) v.findViewById(R.id.btnView);
btnView.setTextColor(Color.RED);
btnView.setEnabled(true);
}
}
class LoadContentFromServer extends AsyncTask<Object, Integer, Object> {
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected Object doInBackground(Object... params) {
HashMap<String, Object> map;
String url = "***** url******";
String result = "";
InputStream is = null;
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
// http post
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
try {
BufferedReader reader = new BufferedReader(
new InputStreamReader(is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
try {
JSONObject json_obj = new JSONObject(result);
JSONArray j_Arr_fn = json_obj.getJSONArray("children");
for (int i = 0; i < j_Arr_fn.length(); i++) {
JSONObject json_objs = j_Arr_fn.getJSONObject(i);
Url_Dto proDto = new Url_Dto();
proDto.url_video = json_objs.getString("videoUrl");
map = new HashMap<String, Object>();
map.put("VideoPathThum", proDto.url_video);
MyArrList.add(map);
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
return null;
}
@Override
protected void onPostExecute(Object result) {
ShowThumbnailData();
}
}
class ImageAdapter extends BaseAdapter {
private Context mContext;
public ImageAdapter(Context context) {
mContext = context;
}
public int getCount() {
return MyArrList.size();
}
public Object getItem(int position) {
return MyArrList.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(final int position, View convertView,
ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater inflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
convertView = inflater.inflate(R.layout.activity_column, null);
}
// ColImage
ImageView imageView = (ImageView) convertView
.findViewById(R.id.ColImgPath);
imageView.getLayoutParams().height = 110;
imageView.getLayoutParams().width = 110;
imageView.setPadding(10, 10, 10, 10);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
try {
imageView.setImageResource(list.get(position).images[position]);
} catch (Exception e) {
// When Error
imageView.setImageResource(android.R.drawable.ic_menu_report_image);
}
// ColStatus
TextView txtStatus = (TextView) convertView
.findViewById(R.id.ColStatus);
txtStatus.setPadding(10, 0, 0, 0);
txtStatus.setText("...");
// btnDownload
final Button btnDownload = (Button) convertView
.findViewById(R.id.btnDownload);
btnDownload.setTextColor(Color.RED);
btnDownload.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Download
btnDownload.setEnabled(false);
btnDownload.setTextColor(Color.GRAY);
startDownload(position);
pbs.setDl(1);
}
});
// btnView
Button btnView = (Button) convertView.findViewById(R.id.btnView);
btnView.setEnabled(false);
btnView.setTextColor(Color.GRAY);
btnView.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
ViewVideoDelete(position);
}
});
// progressBar
ProgressBar progress = (ProgressBar) convertView
.findViewById(R.id.progressBar);
progress.setPadding(10, 0, 0, 0);
return convertView;
}
}
public void ViewVideoDelete(int position) {
String urlDownload = MyArrList.get(position).get("VideoPathThum")
.toString();
String fileName = urlDownload.substring(
urlDownload.lastIndexOf('/') + 1, urlDownload.length());
download = new File(Environment.getExternalStorageDirectory()
+ "/download/");
String strPath = download + "/" + fileName;
Log.v("log_tag", "fileNameDElete :: " + strPath);
File delete = new File(strPath);
delete.delete();
}
}
然后我点击下载按钮然后我向下滚动然后应用程序崩溃。我的错误在下面::
03-05 14:39:15.301: E/AndroidRuntime(4481): FATAL EXCEPTION: main
03-05 14:39:15.301: E/AndroidRuntime(4481): java.lang.NullPointerException
03-05 14:39:15.301: E/AndroidRuntime(4481): at com.example.testhopedownload.TestHopeDownload.updateStatus(TestHopeDownload.java:142)
03-05 14:39:15.301: E/AndroidRuntime(4481): at com.example.testhopedownload.TestHopeDownload.access$1(TestHopeDownload.java:137)
03-05 14:39:15.301: E/AndroidRuntime(4481): at com.example.testhopedownload.TestHopeDownload$1$1.run(TestHopeDownload.java:119)
03-05 14:39:15.301: E/AndroidRuntime(4481): at android.os.Handler.handleCallback(Handler.java:587)
03-05 14:39:15.301: E/AndroidRuntime(4481): at android.os.Handler.dispatchMessage(Handler.java:92)
03-05 14:39:15.301: E/AndroidRuntime(4481): at android.os.Looper.loop(Looper.java:130)
03-05 14:39:15.301: E/AndroidRuntime(4481): at android.app.ActivityThread.main(ActivityThread.java:3683)
03-05 14:39:15.301: E/AndroidRuntime(4481): at java.lang.reflect.Method.invokeNative(Native Method)
03-05 14:39:15.301: E/AndroidRuntime(4481): at java.lang.reflect.Method.invoke(Method.java:507)
03-05 14:39:15.301: E/AndroidRuntime(4481): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-05 14:39:15.301: E/AndroidRuntime(4481): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-05 14:39:15.301: E/AndroidRuntime(4481): at dalvik.system.NativeStart.main(Native Method)