Java 无法在 AsyncTask 中为 ProgressDialog 调用 Looper.prepare() 的线程内创建处理程序
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Can't create handler inside thread that has not called Looper.prepare() inside AsyncTask for ProgressDialog
提问by mlevit
I don't understand why I'm getting this error. I'm using AsyncTask to run some processes in the background.
我不明白为什么我会收到这个错误。我正在使用 AsyncTask 在后台运行一些进程。
I have:
我有：
protected void onPreExecute()
{
connectionProgressDialog = new ProgressDialog(SetPreference.this);
connectionProgressDialog.setCancelable(true);
connectionProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
connectionProgressDialog.setMessage("Connecting to site...");
connectionProgressDialog.show();
downloadSpinnerProgressDialog = new ProgressDialog(SetPreference.this);
downloadSpinnerProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
downloadSpinnerProgressDialog.setMessage("Downloading wallpaper...");
}
When I get into doInBackground()depending on a condition I:
当我进入doInBackground()取决于条件时，我：
[...]
connectionProgressDialog.dismiss();
downloadSpinnerProgressDialog.show();
[...]
Whenever I try downloadSpinnerProgressDialog.show()I receive the error.
每当我尝试时，downloadSpinnerProgressDialog.show()我都会收到错误消息。
Any ideas guys?
有什么想法吗？
采纳答案by Konstantin Burov
The method show()must be called from the User-Interface (UI) thread, while doInBackground()runs on different thread which is the main reason why AsyncTaskwas designed.
该方法show()必须从用户界面 (UI) 线程调用，同时doInBackground()在不同的线程上运行，这是AsyncTask设计的主要原因。
You have to call show()either in onProgressUpdate()or in onPostExecute().
您必须调用show()inonProgressUpdate()或 in onPostExecute()。
For example:
例如：
class ExampleTask extends AsyncTask<String, String, String> {
// Your onPreExecute method.
@Override
protected String doInBackground(String... params) {
// Your code.
if (condition_is_true) {
this.publishProgress("Show the dialog");
}
return "Result";
}
@Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
connectionProgressDialog.dismiss();
downloadSpinnerProgressDialog.show();
}
}
回答by hyui
I had a similar issue but from reading this question I figured I could run on UI thread:
我有一个类似的问题，但从阅读这个问题我想我可以在 UI 线程上运行：
YourActivity.this.runOnUiThread(new Runnable() {
public void run() {
alertDialog.show();
}
});
Seems to do the trick for me.
似乎对我有用。
回答by jayesh kavathiya
final Handler handler = new Handler() {
@Override
public void handleMessage(final Message msgs) {
//write your code hear which give error
}
}
new Thread(new Runnable() {
@Override
public void run() {
handler.sendEmptyMessage(1);
//this will call handleMessage function and hendal all error
}
}).start();
回答by caiocpricci2
I had a hard time making this work too, the solution for me was to use both hyui and konstantin answers,
我也很难完成这项工作，我的解决方案是同时使用 hyui 和 konstantin 的答案，
class ExampleTask extends AsyncTask<String, String, String> {
// Your onPreExecute method.
@Override
protected String doInBackground(String... params) {
// Your code.
if (condition_is_true) {
this.publishProgress("Show the dialog");
}
return "Result";
}
@Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
YourActivity.this.runOnUiThread(new Runnable() {
public void run() {
alertDialog.show();
}
});
}
}
