有人可以告诉我，为什么在上传图片时没有显示进度条。我从我的旧项目中复制了asynctask结构。在我的旧项目中，我使用asynctask从Web服务器下载图片，并在下载时显示进度条。 这是我的代码：
public class PreviewPostActivity extends Activity {
ImageView imageView;
TextView tvComment;
Button submit;
MyLocationListener locationListener;
List<NameValuePair> list = new ArrayList<NameValuePair>();
private final String url = "***"; //Url of php script
ProgressDialog pDialog;
String responseMessage="";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.preview_post);
Intent intent = this.getIntent();
imageView = (ImageView)findViewById(R.id.imgPerview);
tvComment = (TextView)findViewById(R.id.txtPreviewComment);
submit = (Button)findViewById(R.id.btnPreviewSubmit);
Bitmap image = (Bitmap)intent.getParcelableExtra("picture");
String comment = intent.getStringExtra("comment");
locationListener = (MyLocationListener)intent.getSerializableExtra("location");
String imagePath = intent.getStringExtra("imagePath");
String date = intent.getStringExtra("date");
imageView.setImageBitmap(image);
tvComment.setText(comment);
//tvComment.append("\n"+locationListener.latitude + "\n"+locationListener.longitude);
list.add(new BasicNameValuePair("image", imagePath));
list.add(new BasicNameValuePair("comment", comment));
list.add(new BasicNameValuePair("longitude", Double.toString(locationListener.longitude)));
list.add(new BasicNameValuePair("latitude", Double.toString(locationListener.latitude)));
list.add(new BasicNameValuePair("date", date));
submit.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
new uploadPost().execute();
}
});
}
public void post(List<NameValuePair> nameValuePairs) {
HttpParams httpParameters = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParameters, 100000);
HttpConnectionParams.setSoTimeout(httpParameters, 200000);
HttpClient httpClient = new DefaultHttpClient(httpParameters);
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(url);
try {
MultipartEntity entity = new MultipartEntity();
for(int index=0; index < nameValuePairs.size(); index++) {
if(nameValuePairs.get(index).getName().equalsIgnoreCase("image")) {
// If the key equals to "image", we use FileBody to transfer the data
entity.addPart(nameValuePairs.get(index).getName(), new FileBody(new File(nameValuePairs.get(index).getValue()),"image/jpeg"));
} else {
// Normal string data
entity.addPart(nameValuePairs.get(index).getName(), new StringBody(nameValuePairs.get(index).getValue()));
}
}
httpPost.setEntity(entity);
HttpResponse response = httpClient.execute(httpPost, localContext);
HttpEntity httpEntity = response.getEntity();
String responseMessage = EntityUtils.toString(httpEntity);
tvComment.setText(responseMessage);
} catch (IOException e) {
e.printStackTrace();
}
}
class uploadPost extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(PreviewPostActivity.this);
pDialog.setMessage("Uploading post. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Getting product details in background thread
* */
protected String doInBackground(String... params) {
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
//post(list);
HttpParams httpParameters = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParameters, 100000);
HttpConnectionParams.setSoTimeout(httpParameters, 200000);
HttpClient httpClient = new DefaultHttpClient(httpParameters);
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(url);
try {
MultipartEntity entity = new MultipartEntity();
for(int index=0; index < list.size(); index++) {
if(list.get(index).getName().equalsIgnoreCase("image")) {
// If the key equals to "image", we use FileBody to transfer the data
entity.addPart(list.get(index).getName(), new FileBody(new File(list.get(index).getValue()),"image/jpeg"));
} else {
// Normal string data
entity.addPart(list.get(index).getName(), new StringBody(list.get(index).getValue()));
}
}
httpPost.setEntity(entity);
HttpResponse response = httpClient.execute(httpPost, localContext);
HttpEntity httpEntity = response.getEntity();
responseMessage = EntityUtils.toString(httpEntity);
//tvComment.setText(responseMessage);
} catch (IOException e) {
e.printStackTrace();
}
}
});
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once got all details
tvComment.setText(responseMessage);
pDialog.dismiss();
}
}
因此，当我按下按钮进行上传时，屏幕会冻结并保持冻结，直到上传完成，并且进度条根本不显示。有时它显示，但它的后方，我不知道为什么。我已经尝试从doInBackground体内调用Post（）方法，整个代码中的主体（在body中的代码与post（）方法中的相同）但效果是相同的，所以我想我在创建进度条时没有做正确的事情。但我再次说我从旧项目中复制了整个asynctask代码，因为它工作得很好。
编辑：
我刚刚尝试在PreviewPostActivity.class的构造函数中创建进度条，之后我为asynctask类创建了构造函数，但它仍然无法正常工作。我很困惑因为它在我的旧程序中起作用。 这是他的代码：
class GetSlike extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(KlubSlikeActivity.this);
pDialog.setMessage("Ucitavanje u toku. Molimo vas sacekajte...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Getting product details in background thread
* */
protected String doInBackground(String... params) {
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
String id = Integer.toString(k.getId());
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("klub",id));
slikeUrl = JSONAdapter.getSlike(params);
gv.setAdapter(new SlikeAdapter(slikeUrl,KlubSlikeActivity.this));
}
});
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once got all details
pDialog.dismiss();
}
}
唯一改变的是doInBackground body ...
编辑：
执行runOnUiThread()后显示对话框。
答案 0 :(得分：5)
我发现这个库非常适合完成上传任务，还提供了一个进度处理程序，可以用来设置ProgressBar的值：
https://github.com/nadam/android-async-http
可以像下面这样使用...为上传按钮设置onClickHandler：
@Override
public void onClick(View arg0) {
try {
String url = Uri.parse("YOUR UPLOAD URL GOES HERE")
.buildUpon()
.appendQueryParameter("SOME PARAMETER IF NEEDED 01", "VALUE 01")
.appendQueryParameter("SOME PARAMETER IF NEEDED 02", "VALUE 02")
.build().toString();
AsyncHttpResponseHandler httpResponseHandler = createHTTPResponseHandler();
RequestParams params = new RequestParams();
// this path could be retrieved from library or camera
String imageFilePath = "/storage/sdcard/DCIM/Camera/IMG.jpg";
params.put("data", new File(imageFilePath));
AsyncHttpClient client = new AsyncHttpClient();
client.post(url, params, httpResponseHandler);
} catch (IOException e) {
e.printStackTrace();
}
}
然后将此方法添加到您的活动代码中：
public AsyncHttpResponseHandler createHTTPResponseHandler() {
AsyncHttpResponseHandler handler = new AsyncHttpResponseHandler() {
@Override
public void onStart() {
super.onStart();
}
@Override
public void onProgress(int position, int length) {
super.onProgress(position, length);
progressBar.setProgress(position);
progressBar.setMax(length);
}
@Override
public void onSuccess(String content) {
super.onSuccess(content);
}
@Override
public void onFailure(Throwable error, String content) {
super.onFailure(error, content);
}
@Override
public void onFinish() {
super.onFinish();
}
};
return handler;
}
答案 1 :(得分：3)
在asynctask doinbackground（）中运行ui线程不正确。您还在doInBackground（）中返回null，并且在onPostExecute（）中有参数file_url。 doInbackground（）中的返回值在onPostExecute（）中接收值。
doInBackGround（）在后台运行，因此您无法在此处访问或更新ui。
要更新ui，您可以使用onPostExecute（）。
您的AsyncTask应该如下所示。你这样做是错误的。
http://developer.android.com/reference/android/os/AsyncTask.html。 请参阅“4个步骤”
下的主题 pd= new ProgressDialog(this);
pd.setTitle("Posting data");
new PostTask().execute();
private class PostTask extends AsyncTask<VOid, Void, Void> {
protected void onPreExecute()
{//display dialog.
pd.show();
}
protected SoapObject doInBackground(Void... params) {
// TODO Auto-generated method stub
//post request. do not update ui here. runs in background
return null;
}
protected void onPostExecute(Void param)
{
pd.dismiss();
//update ui here
}