Android AsyncTask [无法在未调用 Looper.prepare() 的线程内创建处理程序] [英] Android AsyncTask [Can't create handler inside thread that has not called Looper.prepare()]
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问题描述
我基于一个函数创建了一个图像上传AsyncTask.上传后，我在 onPostExecute() 上收到此错误.我在 Runnable 上阅读了一些 StackOverflow 的答案，但尽管实施了不同的解决方案，但我仍然一遍又一遍地得到错误.
I've created an image upload AsyncTask based on a function. And after uploading, I get this error on onPostExecute(). I read up some StackOverflow answers on Runnable yet I kept getting the error over and over again despite implementing a different solution.
我的代码:
class uploadFile extends AsyncTask<String, String, String> {
private ProgressDialog pDialog;
/**
* --------------------------------------------------------------------
* --------------------------------- Before starting background thread
* Show Progress Dialog
*/
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Uploading file");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* --------------------------------------------------------------------
* --------------------------------- getting all recent articles and
* showing them in listview
*/
@Override
protected String doInBackground(String... args) {
HttpURLConnection conn = null;
DataOutputStream dos = null;
DataInputStream inStream = null;
String existingFileName = Environment.getExternalStorageDirectory()
.getAbsolutePath() + "/mypic.png";
String lineEnd = "
";
String twoHyphens = "--";
String boundary = "*****";
int bytesRead, bytesAvailable, bufferSize;
byte[] buffer;
int maxBufferSize = 1 * 1024 * 1024;
String serverResponseMessage = "";
String urlString = "http://google.info/imgupl/index.php";
try {
// ------------------ CLIENT REQUEST
FileInputStream fileInputStream = new FileInputStream(new File(
existingFileName));
// open a URL connection to the Servlet
URL url = new URL(urlString);
// Open a HTTP connection to the URL
conn = (HttpURLConnection) url.openConnection();
// Allow Inputs
conn.setDoInput(true);
// Allow Outputs
conn.setDoOutput(true);
// Don't use a cached copy.
conn.setUseCaches(false);
// Use a post method.
conn.setRequestMethod("POST");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("Content-Type",
"multipart/form-data;boundary=" + boundary);
dos = new DataOutputStream(conn.getOutputStream());
dos.writeBytes(twoHyphens + boundary + lineEnd);
dos.writeBytes("Content-Disposition: form-data; name="uploadedfile";filename=""
+ existingFileName + """ + lineEnd);
dos.writeBytes(lineEnd);
// create a buffer of maximum size
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
buffer = new byte[bufferSize];
// read file and write it into form...
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
while (bytesRead > 0) {
dos.write(buffer, 0, bufferSize);
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
}
// send multipart form data necesssary after file data...
dos.writeBytes(lineEnd);
dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
// close streams
Integer serverResponseCode = conn.getResponseCode();
serverResponseMessage = conn.getResponseMessage();
Toast.makeText(getApplicationContext(), serverResponseMessage,
Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(),
serverResponseCode.toString(), Toast.LENGTH_SHORT)
.show();
Log.e("Debug", "File is written");
fileInputStream.close();
dos.flush();
dos.close();
} catch (MalformedURLException ex) {
Log.e("Debug", "error: " + ex.getMessage(), ex);
} catch (IOException ioe) {
Log.e("Debug", "error: " + ioe.getMessage(), ioe);
}
// ------------------ read the SERVER RESPONSE
try {
inStream = new DataInputStream(conn.getInputStream());
while ((str = inStream.readLine()) != null) {
Log.e("Debug", "Server Response " + str);
}
inStream.close();
} catch (IOException ioex) {
Log.e("Debug", "error: " + ioex.getMessage(), ioex);
}
return null;
}
/**
* --------------------------------------------------------------------
* --------------------------------- After completing background task
* Dismiss the progress dialog
**/
protected void onPostExecute(String args) {
// dismiss the dialog after getting all products
pDialog.dismiss();
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(MainActivity.this, "Hello", Toast.LENGTH_SHORT).show();
}
});
}
}
我的日志:
08-13 22:13:32.627: E/AndroidRuntime(9554): FATAL EXCEPTION: AsyncTask #1
08-13 22:13:32.627: E/AndroidRuntime(9554): java.lang.RuntimeException: An error occured while executing doInBackground()
08-13 22:13:32.627: E/AndroidRuntime(9554): at android.os.AsyncTask$3.done(AsyncTask.java:200)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.lang.Thread.run(Thread.java:1019)
08-13 22:13:32.627: E/AndroidRuntime(9554): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
08-13 22:13:32.627: E/AndroidRuntime(9554): at android.os.Handler.<init>(Handler.java:121)
08-13 22:13:32.627: E/AndroidRuntime(9554): at android.widget.Toast.<init>(Toast.java:68)
08-13 22:13:32.627: E/AndroidRuntime(9554): at android.widget.Toast.makeText(Toast.java:231)
08-13 22:13:32.627: E/AndroidRuntime(9554): at dev.google.imageupload.MainActivity$uploadFile.doInBackground(MainActivity.java:128)
08-13 22:13:32.627: E/AndroidRuntime(9554): at dev.google.imageupload.MainActivity$uploadFile.doInBackground(MainActivity.java:1)
08-13 22:13:32.627: E/AndroidRuntime(9554): at android.os.AsyncTask$2.call(AsyncTask.java:185)
08-13 22:13:32.627: E/AndroidRuntime(9554): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
08-13 22:13:32.627: E/AndroidRuntime(9554): ... 4 more
根据 zapl 的建议进行
EDITED after zapl's suggestion :
08-13 22:38:06.297: E/AndroidRuntime(11511): FATAL EXCEPTION: AsyncTask #1
08-13 22:38:06.297: E/AndroidRuntime(11511): java.lang.RuntimeException: An error occured while executing doInBackground()
08-13 22:38:06.297: E/AndroidRuntime(11511): at android.os.AsyncTask$3.done(AsyncTask.java:200)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.lang.Thread.run(Thread.java:1019)
08-13 22:38:06.297: E/AndroidRuntime(11511): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
08-13 22:38:06.297: E/AndroidRuntime(11511): at android.os.Handler.<init>(Handler.java:121)
08-13 22:38:06.297: E/AndroidRuntime(11511): at android.widget.Toast.<init>(Toast.java:68)
08-13 22:38:06.297: E/AndroidRuntime(11511): at android.widget.Toast.makeText(Toast.java:231)
08-13 22:38:06.297: E/AndroidRuntime(11511): at dev.google.imageupload.MainActivity$uploadFile.doInBackground(MainActivity.java:128)
08-13 22:38:06.297: E/AndroidRuntime(11511): at dev.google.imageupload.MainActivity$uploadFile.doInBackground(MainActivity.java:1)
08-13 22:38:06.297: E/AndroidRuntime(11511): at android.os.AsyncTask$2.call(AsyncTask.java:185)
08-13 22:38:06.297: E/AndroidRuntime(11511): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
08-13 22:38:06.297: E/AndroidRuntime(11511): ... 4 more
推荐答案
您正试图从后台线程更新 UI.要么将 toast 移动到 onPostExecute，它在 UI 线程上执行(推荐)，要么调用 runOnUiThread.
You are attempting to update the UI from a background thread. Either move the toast to onPostExecute, which executes on the UI thread (recommended), or call runOnUiThread.
runOnUiThread(new Runnable() {
public void run() {
// runs on UI thread
}
});
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