7.9. EraseImageDialogFragment Class

Class EraseImageDialogFragment (Fig. 7.40) extends DialogFragment to create an AlertDialog that confirms whether the user really wants to erase the entire image. The class is similar to class ColorDialogFragment and LineWidthDialogFragment, so we discuss only method onCreateDialog (lines 16–41) here. The method creates an AlertDialog with Erase Image and Cancel button. Lines 27–35 configure the Erase Image button as the positive button—when the user touches this, line 32 in the button’s listener calls the DoodleView’s clear method to erase the image. Line 38 configures Cancel as the negative button—when the user touches this, the dialog is dismissed. Line 40 returns the AlertDialog.

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 1   // EraseImageDialogFragment.java
 2   // Allows user to erase image
 3   package com.deitel.doodlz;
 4
 5   import android.app.Activity;
 6   import android.app.AlertDialog;
 7   import android.app.Dialog;
 8   import android.app.DialogFragment;
 9   import android.content.DialogInterface;
10   import android.os.Bundle;
11
12   //class for the Select Color dialog
13   public class EraseImageDialogFragment extends DialogFragment
14   {
15      // create an AlertDialog and return it
16      @Override
17      public Dialog onCreateDialog(Bundle bundle)
18      {
19         AlertDialog.Builder builder =
20            new AlertDialog.Builder(getActivity());
21
22         // set the AlertDialog's message
23         builder.setMessage(R.string.message_erase);
24         builder.setCancelable(false);
25
26         // add Erase Button
27         builder.setPositiveButton(R.string.button_erase,
28            new DialogInterface.OnClickListener()
29            {
30               public void onClick(DialogInterface dialog, int id)
31               {
32                  getDoodleFragment().getDoodleView().clear(); // clear image
33               }
34            }
35         ); // end call to setPositiveButton
36
37         // add Cancel Button
38         builder.setNegativeButton(R.string.button_cancel, null);
39
40         return builder.create(); // return dialog
41      } // end method onCreateDialog
42
43      // gets a reference to the DoodleFragment
44      private DoodleFragment getDoodleFragment()
45      {
46         return (DoodleFragment) getFragmentManager().findFragmentById(
47            R.id.doodleFragment);
48      }
49
50      // tell DoodleFragment that dialog is now displayed
51      @Override
52      public void onAttach(Activity activity)
53      {
54         super.onAttach(activity);
55         DoodleFragment fragment = getDoodleFragment();
56
57         if (fragment != null )
58            fragment.setDialogOnScreen(true );
59      }
60
61      // tell DoodleFragment that dialog is no longer displayed
62      @Override
63      public void onDetach()
64      {
65         super.onDetach();
66         DoodleFragment fragment = getDoodleFragment();
67
68         if (fragment != null )
69            fragment.setDialogOnScreen(false);
70      }
71   } // end class EraseImageDialogFragment

Fig. 7.40 | Class EraseImageDialogFragment.