安卓：在列表视图特定项目更改图片视图、项目、列表、图片
在上面的图像，存在其中包含的用户可下载的产品清单的列表视图。 这是告诉用户，他可以下载该文件的图像。在下载完成后，图像将变为。我的问题是，当我下载一个文件后，状态图像（这表示该下载完成）被改变为另一行，相反，它应该改变，我已经选择的行。在present，如果我下载第一个文件列表，图像被改变为列表中的第4或第5项。此外，当我尝试从列表中下载任何其他文件。它开辟了最后下载的文件（这是该应用程序的功能，如果已经下载的文件，然后在pdf阅读器打开它），也就是说，如果我下载1号文件中的列表，然后再进行第二个项目，则不是下载2日文件，它开辟了最后下载的文件。更过，如果我滚动列表视图，下载的状态得到改变在列表中还包括其他项目。下面是我的适配器code：
In the above image, there is a list view which contains list of items that the user can download. This is the image which tells user that he can download the file. On completion of download, the image will change to . My problem is when I download a file, the status image(which denotes that download has completed) gets changed for another row, instead, it should change for the row that I had selected. At present, if I download first file in the list, the image gets changed for 4th or 5th item in the list. Also, when I try to download any other file from the list. it opens up last downloaded file(This is functionality of the app that if file is already downloaded, then open it in pdf reader),i.e., if I download 1st file in the list and then go for second item,then instead of downloading 2nd file, it opens up last downloaded file. More over, if I scroll the listview, the status of download gets changed for other items in the list also. Below,is my adapter code:
public class DownloadListAdapter extends BaseAdapter {
Context ctx;
public ArrayList<DownloadListDao> mDownloadList;
String readMoreLink;
public static final String TAG = "DownloadListAdapter";
ProgressDialog mProgressDialog;
private boolean isSDCardPresent;
File tieDir;
int downloadState[];
public DownloadListAdapter(Context ctx,
ArrayList<DownloadListDao> mDownloadList) {
this.ctx = ctx;
this.mDownloadList = mDownloadList;
downloadState = new int [mDownloadList.size()];
for(int i = 0; i < mDownloadList.size(); i++) {
downloadState[i] = 0;
}
tieDir = new File(Environment.getExternalStorageDirectory().toString()
+ "/tie");
}// Constructor
public int getCount() {
return this.mDownloadList.size();
}// getCount
public Object getItem(int position) {
return this.mDownloadList.get(position);
}// getItem
public long getItemId(int position) {
return 0;
}// getItemId
static class ViewHolder {
TextView txtTitle, txtTheme, txtDate;
ImageView imgDownload;
}// ViewHolder
ViewHolder holder;
public View getView(final int position, View convertView, ViewGroup parent) {
final String url = mDownloadList.get(position).getUrl();
if (convertView == null) {
convertView = LayoutInflater.from(parent.getContext()).inflate(
R.layout.downlist_adapter, null);
holder = new ViewHolder();
holder.txtTitle = (TextView) convertView
.findViewById(R.id.txtTitle);
holder.txtTheme = (TextView) convertView
.findViewById(R.id.txtTheme);
holder.txtDate = (TextView) convertView.findViewById(R.id.txtDate);
holder.imgDownload = (ImageView) convertView
.findViewById(R.id.imgDload);
holder.imgDownload.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
File mediaFile = null;
if (url != null && !url.equals("null") && !url.equals("")) {
String fileName = url.toString().substring(
url.toString().lastIndexOf("/") + 1,
url.toString().length());
mediaFile = new File(tieDir, fileName);
}
processFile(mediaFile, url, position);
int pos = (Integer)v.getTag();
downloadState[pos] = 1;
}
});
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
if (mDownloadList != null && mDownloadList.size() > 0) {
if (mDownloadList.get(position).getTitle() != null
&& !mDownloadList.get(position).getTitle().equals("null")
&& !mDownloadList.get(position).getTitle().equals("")) {
holder.txtTitle.setText(mDownloadList.get(position).getTitle());
}
if (mDownloadList.get(position).getTheme() != null
&& !mDownloadList.get(position).getTheme().equals("null")
&& !mDownloadList.get(position).getTheme().equals("")) {
holder.txtTheme.setText(mDownloadList.get(position).getTheme());
}
if (mDownloadList.get(position).getDate() != null
&& !mDownloadList.get(position).getDate().equals("null")
&& !mDownloadList.get(position).getDate().equals("")) {
holder.txtDate.setText(mDownloadList.get(position).getDate());
}
if (downloadState[position] == 1) {
holder.imgDownload.setImageDrawable(ctx.getResources()
.getDrawable(R.drawable.ic_dloaded));
} else {
holder.imgDownload.setImageDrawable(ctx.getResources()
.getDrawable(R.drawable.ic_dload));
}
}
holder.imgDownload.setTag(position);
return convertView;
}// getView
protected void downloadFile(String url, int position, String fileName) {
Log.v(TAG, "Preparing to download");
mProgressDialog = new ProgressDialog(ctx);
mProgressDialog.setMessage("Dowloading...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.setMax(100);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
isSDCardPresent = Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED);
if (!isSDCardPresent) {
noSDCardAlert(ctx);
} else {
if ((tieDir.exists()) && (tieDir != null)) {
if (NetworkConnection.isOnline(ctx)) {
if (tieDir.isDirectory()) {
Log.v(TAG, "if tie dir URL:::" + url);
new DownloadAudioAsync(ctx, position, fileName).execute(url);
}
} else {
((DownloadListActivity) ctx)
.OpenNetErrDialog("Please check your internet connection...");
}
} else {
boolean isDirectoryCreated = tieDir.mkdirs();
if (isDirectoryCreated) {
Log.v(TAG, "if tie not dir URL:::" + url);
if (NetworkConnection.isOnline(ctx)) {
new DownloadAudioAsync(ctx, position, fileName).execute(url);
} else {
((DownloadListActivity) ctx)
.OpenWiFiDialog("Please check your internet connection...");
}
}
}
}
}
private void noSDCardAlert(Context ctx) {
AlertDialog.Builder ad = new AlertDialog.Builder(ctx);
ad.setMessage("No sd card present..");
ad.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
if (!((DownloadDetail) ctx).isFinishing()) {
ad.show();
}
}
public void OpenDialog(String messageID) {
final Dialog dialog = new Dialog(ctx,
android.R.style.Theme_Translucent_NoTitleBar);
dialog.setContentView(R.layout.dialog_base);
dialog.getWindow().getAttributes().windowAnimations = android.R.style.Animation_Dialog;
dialog.setCancelable(false);
TextView alertMessage = (TextView) dialog.findViewById(R.id.txtMessage);
Button btnOK = (Button) dialog.findViewById(R.id.btnOk);
btnOK.setText("Show");
alertMessage.setText(messageID);
dialog.show();
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
}
});
}
protected void showPdf(File mediaFile) {
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(mediaFile), "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
ctx.startActivity(intent);
}
public class DownloadAudioAsync extends AsyncTask<String, String, String> {
Context ctx;
int pos;
private ProgressDialog pd;
String fileName;
public DownloadAudioAsync(Context ctx, int pos, String fileName) {
this.ctx = ctx;
this.pos = pos;
this.fileName = fileName;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
Log.v(TAG, "inside on pre execute");
pd = new ProgressDialog(ctx);
pd.setMessage("Downloading...\nPlease wait..");
pd.show();
}
@Override
protected String doInBackground(String... aurl) {
int count;
try {
Log.v(TAG,
"inside do in background with url::"
+ aurl[0].toString());
aurl[0] = aurl[0].replaceAll(" ", "%20");
URL url = new URL(aurl[0]);
URLConnection conexion = url.openConnection();
conexion.connect();
int lenghtOfFile = conexion.getContentLength();
fileName = URLDecoder.decode(fileName, "UTF-8");
InputStream input = new BufferedInputStream(url.openStream());
OutputStream output = new FileOutputStream(tieDir + "/"
+ fileName);
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
publishProgress("" + (int) ((total * 100) / lenghtOfFile));
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
} catch (Exception e) {
}
return null;
}
@Override
protected void onPostExecute(String unused) {
if (!((DownloadListActivity) ctx).isFinishing()) {
pd.dismiss();
updateView(pos);
}
}
private void updateView(int pos) {
View v = ((DownloadListActivity) ctx).menuListView.getChildAt(pos
- ((DownloadListActivity) ctx).menuListView
.getFirstVisiblePosition());
ImageView imgDloadBtn = (ImageView) v.findViewById(R.id.imgDload);
imgDloadBtn.setImageDrawable(ctx.getResources().getDrawable(
R.drawable.ic_dloaded));
notifyDataSetChanged();
}
}
private void processFile(File mediaFile, String url, int pos) {
if (url != null && !url.equals("null") && !url.equals("")) {
if (mediaFile != null) {
Log.v(TAG, "in processFile FileName " + mediaFile.getName());
Log.v(TAG, "in processFile Position " + pos);
if(!mediaFile.exists()) {
Log.v(TAG, "in processFile Media file doesn't exists");
downloadFile(url, pos, mediaFile.getName());
} else {
Log.v(TAG, "in processFile Media file exists");
try {
showPdf(mediaFile);
} catch (ActivityNotFoundException anfe) {
OpenDialog("PDF Reader is not installed on your device.");
}
}
}
}
}
}// DownloadAdapter
我读this帖子回收的观点（感谢 Knickedi 以深入的解释）。但是，我想不出哪里是实际的问题。
I had read this post for recycling the view(Thanks to Knickedi for in depth explaination). But, I can't figure out where is actual problem.
推荐答案
问题 getview 方法，让每当你滚动视图，来处理你必须精确位置重建与 setTag和放大器发挥; getTag ，检查以下几个stackvoerflow答案理解 setTag和放大器; getTag ：
Issue with getview Method which keep recreating whenever you scroll your view, to handle exact position you have to play with setTag & getTag,check below few stackvoerflow answers to understand setTag & getTag:
使用按钮ListView中ArrayAdapter
获取单选按钮值从安卓自定义列表
甚至商店下载的状态到一个 booleanArray中象下面这样：
and even store downloaded state into one booleanarray like below:
int boxState[];
在适配器构造函数中，最初设置为零：
within adapter constructor, set zero initially:
for (int i = 0; i < getData.size(); i++) {
boxState[i] = 0;
}
在适配器getview方式：
within adapter getview method:
holder.imgDownload.setTag(position);
现在你点击下载按钮设定值1（内部按钮的onclick）：
Now you click on download button set value as 1 (Inside onclick of button):
pos = (Integer) v.getTag();
boxState[pos]=1;
最后，当您滚动视图检查条件为下面的方式（把下面code里面getview法）：
At last when you scroll your view check condition into following way(put below code inside getview method):
if (boxState[position] == 0) {
holder.imgDownload.setImageDrawable(ctx.getResources()
.getDrawable(R.drawable.ic_dloaded)); //which aren't downloaded
} else {
holder.imgDownload.setImageDrawable(ctx.getResources()
.getDrawable(R.drawable.ic_dload)); // which are downloaded.
}
