Android Progressbar在错误的时间启动

Question

I try to launch a progressbar in my application but wehn I launch it the BAr isn't show before the function is started

public void onClick(View v) {

if (v == button)
{
    ProgressDialog dialog = ProgressDialog.show(App.this, "", 
            "Loading. Please wait...", true);
    dialog.show();
try
{

    directory = edittext.getText().toString();
    FileWriter fstream = new FileWriter("/data/data/folder.hide.alexander.fuchs/folder.db");
    BufferedWriter out = new BufferedWriter(fstream);
    out.write(directory);
    //Close the output stream
    out.close();
if(hide_or_show == "hide")
{



    edittext.setVisibility(View.INVISIBLE);
    folder_to_hide.setVisibility(View.INVISIBLE);
    hide();

    dialog.dismiss();
}
else
{   


    show();
    edittext.setVisibility(View.VISIBLE);
    folder_to_hide.setVisibility(View.VISIBLE);

    dialog.dismiss();
}
}
catch(Exception x)
{       
    String ErrorMessage = x.getMessage();
    Toast.makeText(this,"Error"+ErrorMessage, Toast.LENGTH_LONG).show();
    finish();
}
}
if (v == options)
{
    final CharSequence[] items = {"Change password", "http://www.alexander-fuchs.net/", "Market"};

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Options");
    builder.setItems(items, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int item) {

            if (items[item] == "Change password")
            {
                createpass();

            }
            if (items[item] == "http://www.alexander-fuchs.net/")
            {
            intentstarter(items[item].toString());
           toaster(items[item].toString());
            }
            if (items[item] == "Market")
            {
            intentstarter("market://search?q=pub:Alexander Fuchs");
            toaster("Please wait...");
            }
        }
    });
    AlertDialog alert = builder.create();
    alert.show();
}
}

when I tap the button it takes long to respond and then the whole function finishs without prompting an progressbar

Answer 1

onClick is a callback where the return to Android is only returned when the callback ends. All UI interaction you do basically is collected and queued while the callback is active and executed after return (may not technically totally accurate).

For you ProgressBar to show up at the start of the action and vanish at the end, you can implement an AsyncTask where the progress bar is shown in onPreExecute , the real computation is done in doInBackground and the progressbar is dismissed in onPostExecute . For example:

 protected void onPreExecute() {
        dialog = new ProgressDialog(context);
        dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        dialog.show();
 }

 protected void onPostExecute(Map<Integer, String> integerStringMap) {
        if (dialog!=null)
            dialog.cancel();
 }

 protected void onProgressUpdate(Integer... values) {
        int val = values[0]*10000/num;
        dialog.setProgress(val);
 }

See here for the more complete example.