进程运行时，在Asnyctask中运行进度对话框

Question

我正在尝试运行以下代码，但是我想在运行过程时显示一个进度对话框：

public boolean isOnline() {
    cm = (ConnectivityManager) mContext.getSystemService(mContext.CONNECTIVITY_SERVICE);
    netInfo = cm.getActiveNetworkInfo();

    progress_thread = new progress_thread();
    progress_thread.execute();

    isconnected = false;
    if (netInfo != null && netInfo.isConnected()) {
        try{
            URL url = new URL("http://www.google.com");
            HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
            urlc.setConnectTimeout(3000);
            urlc.connect();
            if (urlc.getResponseCode() == 200)  isconnected = true;

        }catch (MalformedURLException e1) {
            e1.printStackTrace();
        }catch (IOException e) {
            e.printStackTrace();
        }
    }



    progress_thread.cancel(true);
    if (!isconnected) Toast.makeText(mContext,"Internet Connexion Error", Toast.LENGTH_LONG).show();

    return isconnected;

private class progress_thread extends AsyncTask<Void, Integer, Boolean>{

    protected void onPreExecute() { 

        dialog = new ProgressDialog(mContext); 
        dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        dialog.setMessage("Loading Tracker...");
        dialog.setCancelable(false);
        dialog.show();
    }

    protected Boolean doInBackground(Void... params) {
        try {
            Thread.sleep(60000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return true;
    }

    protected void onCancelled() {
        if (dialog.isShowing()) dialog.dismiss();
    }

    protected void onPostExecute(Boolean result_ex) {
        if (dialog.isShowing()) dialog.dismiss();
    }
}

我想做的是在检查是否有Internet连接时运行进度对话框。 但是我有一个问题，UI没有刷新，进度对话框没有显示出来，就像我想要的那样。

Answer 1

您这样做的方式是通过检查Internet连接来占用UI线程。 这使窗口管理器无法处理ProgressDialog显示。

您应该将此检查以及显示进度对话框一起移至AsyncTask ，如下所示：

private void startOnlineCheck() {
    ProgressThread progress_thread = new ProgressThread();
    progress_thread.execute();
}

private class ProgressThread extends AsyncTask<Void, Void, Void>{
    ProgressDialog dialog;

    protected void onPreExecute() { 
        dialog = new ProgressDialog(Activity.this); 
        dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        dialog.setMessage("Loading Tracker...");
        dialog.setCancelable(false);
        dialog.show();
    }

    protected Void doInBackground(Void... params) {
        ConnectivityManager cm = (ConnectivityManager) Activity.this.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnected()) {
            try{
                URL url = new URL("http://www.google.com");
                HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
                urlc.setConnectTimeout(3000);
                urlc.connect();
                // CODE to run when we're online
                return null;
            }catch (MalformedURLException e1) {
                e1.printStackTrace();
            }catch (IOException e) {
                e.printStackTrace();
            }
        }
        Toast.makeText(Activity.this, "Internet Connexion Error", Toast.LENGTH_LONG).show();
        // CODE to run when there's no connection
        return null;
    }

    protected void onPostExecute(Void result) {
        if (dialog.isShowing()) dialog.dismiss();
    }
}

您还可以在构造函数中将Context传递给ProgressThread 。

请记住，如果ProgressThread是Activity的内部类（通常是这种情况），则可以从ProgressThread任何方法调用该活动的任何方法。