AlertDialog setmessage 在 Asynctask 中不起作用
AlertDialog setmessage not working inside Asynctask
下面是我的代码,我试图通过 onProgressUpdate 方法在 Asyntask 中显示我的进度,但它没有显示在警报对话框中。仅显示初始消息。
class DownloadFileFromURL extends AsyncTask<String, String, String> {
private AlertDialog.Builder alert;
private int progress = 0;
/**
* Before starting background thread Show Progress Bar Dialog
*/
@Override
protected void onPreExecute() {
super.onPreExecute();
alert = new AlertDialog.Builder(context);
alert.setTitle("Downloading..");
alert.setMessage("1");
alert.setCancelable(false);
alert.show();
}
/**
* Downloading file in background thread
*/
@Override
protected String doInBackground(String... f_url) {
int count;
try {
URL url = new URL(f_url[0]);
URLConnection conection = url.openConnection();
conection.connect();
// this will be useful so that you can show a tipical 0-100%
// progress bar
int lenghtOfFile = conection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream(),
8192);
// Output stream
OutputStream output = new FileOutputStream(file);
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
// After this onProgressUpdate will be called
publishProgress("" + (int) ((total * 100) / lenghtOfFile));
// writing data to file
output.write(data, 0, count);
}
// flushing output
output.flush();
// closing streams
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
/**
* Updating progress bar
*/
@Override
protected void onProgressUpdate(String... progress) {
Log.d("Myapp","progress :"+progress[0]);
alert.setMessage(""+progress[0]);
}
/**
* After completing background task Dismiss the progress dialog
**/
@Override
protected void onPostExecute(String file_url) {
// dismiss the dialog after the file was downloaded
}
}
因为我也在 onProgressUpdate 中写了一个日志来显示进度更新,所以打印了日志,但是 onProgressUpdate 中的 alert.setMessage 似乎没有将消息设置到我的警报对话框。
根据您的代码,alert
是一个 AlertDialog.Builder
而不是 AlertDialog
本身。这引起了我的关注,因为它可能不会更改的原因是因为您已经展示了构建器,但没有提供 AlertDialog
。所以我尝试了一个简单的代码:
public class MainActivity extends AppCompatActivity {
private AlertDialog.Builder alert;
private AlertDialog ad;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
alert = new AlertDialog.Builder(this);
alert.setTitle("Downloading..");
alert.setMessage("1");
alert.setCancelable(false);
ad = alert.show();
Log.d("SAMPLE", "SET MESSAGE 2");
alert.setMessage("2");
Log.d("SAMPLE", "SET MESSAGE 3");
ad.setMessage("3");
}
}
起初,我只是使用了alert.setMessage
(这是AlertDialog.Builder
),消息根本没有改变。但是放在一个AlertDialog
然后设置AlertDialog
实例的消息后,消息就变了。小心尝试这种方法。首先将 AlertDialog.Builder
传递给 AlertDialog
,然后 setMessage
使用 AlertDialog
实例。
AlertDialog and AlertDialog.Builder 的文档。
在您的代码中,您忘记构建警报对话框。看到这个
AlertDialog alertDialog = alert.create();
alertDialog.show();
您必须从 private AlertDialog.Builder alert;
创建一个警告对话框
下面是我的代码,我试图通过 onProgressUpdate 方法在 Asyntask 中显示我的进度,但它没有显示在警报对话框中。仅显示初始消息。
class DownloadFileFromURL extends AsyncTask<String, String, String> {
private AlertDialog.Builder alert;
private int progress = 0;
/**
* Before starting background thread Show Progress Bar Dialog
*/
@Override
protected void onPreExecute() {
super.onPreExecute();
alert = new AlertDialog.Builder(context);
alert.setTitle("Downloading..");
alert.setMessage("1");
alert.setCancelable(false);
alert.show();
}
/**
* Downloading file in background thread
*/
@Override
protected String doInBackground(String... f_url) {
int count;
try {
URL url = new URL(f_url[0]);
URLConnection conection = url.openConnection();
conection.connect();
// this will be useful so that you can show a tipical 0-100%
// progress bar
int lenghtOfFile = conection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream(),
8192);
// Output stream
OutputStream output = new FileOutputStream(file);
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
// After this onProgressUpdate will be called
publishProgress("" + (int) ((total * 100) / lenghtOfFile));
// writing data to file
output.write(data, 0, count);
}
// flushing output
output.flush();
// closing streams
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
/**
* Updating progress bar
*/
@Override
protected void onProgressUpdate(String... progress) {
Log.d("Myapp","progress :"+progress[0]);
alert.setMessage(""+progress[0]);
}
/**
* After completing background task Dismiss the progress dialog
**/
@Override
protected void onPostExecute(String file_url) {
// dismiss the dialog after the file was downloaded
}
}
因为我也在 onProgressUpdate 中写了一个日志来显示进度更新,所以打印了日志,但是 onProgressUpdate 中的 alert.setMessage 似乎没有将消息设置到我的警报对话框。
根据您的代码,alert
是一个 AlertDialog.Builder
而不是 AlertDialog
本身。这引起了我的关注,因为它可能不会更改的原因是因为您已经展示了构建器,但没有提供 AlertDialog
。所以我尝试了一个简单的代码:
public class MainActivity extends AppCompatActivity {
private AlertDialog.Builder alert;
private AlertDialog ad;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
alert = new AlertDialog.Builder(this);
alert.setTitle("Downloading..");
alert.setMessage("1");
alert.setCancelable(false);
ad = alert.show();
Log.d("SAMPLE", "SET MESSAGE 2");
alert.setMessage("2");
Log.d("SAMPLE", "SET MESSAGE 3");
ad.setMessage("3");
}
}
起初,我只是使用了alert.setMessage
(这是AlertDialog.Builder
),消息根本没有改变。但是放在一个AlertDialog
然后设置AlertDialog
实例的消息后,消息就变了。小心尝试这种方法。首先将 AlertDialog.Builder
传递给 AlertDialog
,然后 setMessage
使用 AlertDialog
实例。
AlertDialog and AlertDialog.Builder 的文档。
在您的代码中,您忘记构建警报对话框。看到这个
AlertDialog alertDialog = alert.create();
alertDialog.show();
您必须从 private AlertDialog.Builder alert;