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Conclusion of a dialog box from a stream other than UI

I am developing a network application that focuses on groups. The fact is that when I am going to join a group, it first checks if the group is safe, and if so, it asks for a user and password. Getting group security can take a couple of seconds, so I'm creating a new thread for the whole process. I would like to open a dialogue if the group requires security. I think this may be due to background threads, they may not display dialog boxes ... But the fact is that I need to check the security of the group in the background thread, because it takes a little time.

I hope someone can come up with a solution or ask the user / pass in any way only when the group is safe. Here's the background thread:

public void run() { secInf = mGroupId.getSecurityInformation(); if (secInf.getAdmissionLevel() == CreateGroupDialog.PRIVATE_KEY_ACCESS) { showUserPasswordDialog(); } else { mService.joinGroup(mGroupId); // Notifies handler to dismiss ProgresDialog and start activity mHandler.sendMessage(Message.obtain(mHandler, GroupsActivity.JOIN_SUCCESSFUL)); }

Where showUserPasswordDialog does (mActivity is the activity that spawned this thread):

  private void showUserPasswordDialog() { AlertDialog dialog; // add this to your code // This example shows how to add a custom layout to an AlertDialog LayoutInflater factory = LayoutInflater.from(mActivity); final View textEntryView = factory.inflate( R.layout.alert_dialog_text_entry, null); AlertDialog.Builder builder = new AlertDialog.Builder(mActivity); builder.setIcon(R.drawable.alert_dialog_icon); builder.setTitle(R.string.ask_user_password); builder.setView(textEntryView); builder.setPositiveButton(R.string.ok_text, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { String userName = ((EditText) mActivity .findViewById(R.id.username_edit_alert_dialog)) .getText().toString(); String password = ((EditText) mActivity .findViewById(R.id.password_edit_alert_dialog)) .getText().toString(); Credentials cred = new CredentialsL1(userName, password); mSmeppService.joinGroup(mGroupId, cred); mHandler.sendMessage(Message.obtain(mHandler, GroupsActivity.JOIN_SUCCESSFUL)); }); builder.setNegativeButton(R.string.cancel_text, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { dialog.cancel(); mHandler.sendMessage(Message.obtain(mHandler, GroupsActivity.DISMISS_PROGRESS_DIALOG)); } }); dialog = builder.create(); /* I found this somewhere, but didn't work either */ // Window window = dialog.getWindow(); // WindowManager.LayoutParams lp = window.getAttributes(); // lp.token = textEntryView.getWindowToken(); // lp.type = WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG; // window.setAttributes(lp); // window.addFlags(WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM); dialog.show(); }

I get this exception:

 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): FATAL EXCEPTION: Thread-38 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): android.view.InflateException: Binary XML file line #17: Error inflating class android.widget.EditText 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.createView(LayoutInflater.java:513) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:56) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:563) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.rInflate(LayoutInflater.java:618) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.inflate(LayoutInflater.java:407) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.inflate(LayoutInflater.java:320) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.inflate(LayoutInflater.java:276) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at org.pfc.threads.GroupJoinerThread.showUserPasswordDialog(GroupJoinerThread.java:76) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at org.pfc.threads.GroupJoinerThread.run(GroupJoinerThread.java:52) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): Caused by: java.lang.reflect.InvocationTargetException 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.widget.EditText.<init>(EditText.java:51) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at java.lang.reflect.Constructor.constructNative(Native Method) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at java.lang.reflect.Constructor.newInstance(Constructor.java:446) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.view.LayoutInflater.createView(LayoutInflater.java:500) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): ... 8 more 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.os.Handler.<init>(Handler.java:121) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.text.method.MetaKeyKeyListener$MetaKeyDropbackHandler.<init>(MetaKeyKeyListener.java:605) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.text.method.MetaKeyKeyListener.<init>(MetaKeyKeyListener.java:96) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.text.method.BaseKeyListener.<init>(BaseKeyListener.java:25) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.text.method.TextKeyListener.<init>(TextKeyListener.java:66) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.text.method.TextKeyListener.getInstance(TextKeyListener.java:83) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.widget.TextView.<init>(TextView.java:806) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): at android.widget.EditText.<init>(EditText.java:55) 12-13 19:18:31.823: ERROR/AndroidRuntime(1702): ... 12 more

XML Layout File:

  <EditText android:id="@+id/username_edit_alert_dialog" android:enabled="false" android:layout_height="wrap_content" android:layout_width="fill_parent" android:layout_marginLeft="20dip" android:layout_marginRight="20dip" android:scrollHorizontally="true" android:autoText="false" android:capitalize="none" android:gravity="fill_horizontal" android:textAppearance="?android:attr/textAppearanceMedium" /> <!-- Password --> <TextView android:id="@+id/password_view" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_marginLeft="20dip" android:layout_marginRight="20dip" android:text="@string/password_view_text" android:gravity="left" android:textAppearance="?android:attr/textAppearanceMedium" /> <EditText android:id="@+id/password_edit_alert_dialog" android:enabled="false" android:layout_height="wrap_content" android:layout_width="fill_parent" android:layout_marginLeft="20dip" android:layout_marginRight="20dip" android:scrollHorizontally="true" android:autoText="false" android:capitalize="none" android:gravity="fill_horizontal" android:password="true" android:textAppearance="?android:attr/textAppearanceMedium" />

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2 answers

You are correct that you cannot perform user interface operations from a background thread. To do this, use the Handler that you already implemented to open the dialog box. So something like:

 private Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { switch(msg.what){ case GroupsActivity.DISMISS_PROGRESS_DIALOG: //your existing dismiss code break; case GroupsActivity.CREATE_PROGRESS_DIALOG: //create the dialog break; } } };

Then your launch method will look like this:

 public void run() { secInf = mGroupId.getSecurityInformation(); if (secInf.getAdmissionLevel() == CreateGroupDialog.PRIVATE_KEY_ACCESS) { // do stuff mHandler.sendMessage(Message.obtain(mHandler, GroupsActivity.CREATE_PROGRESS_DIALOG)); // do more stuff } else { mService.joinGroup(mGroupId); // Notifies handler to dismiss ProgresDialog and start activity mHandler.sendMessage(Message.obtain(mHandler, GroupsActivity.JOIN_SUCCESSFUL)); } }
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You're right. Background threads cannot open dialog boxes. You will need a Handler in your user interface thread to open a dialog box for you.

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