Create a Notepad and To-do list combined app in Android

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10. The Alert Dialog

We will now create the various menus and dialogs in the application. Also, we will handle the various onclick events generated when user clicks an item.

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We show this dialog when user clicks the new note button at the bottom of the screen. Add the following line to the ImageButton tag in tab_browse.xml layout file.

	android:onClick="onClick"
					

We need to implement the same onClick function in BrowseActivity class to handle the on click event.

	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.new_btn:
			optionsDialog.show();
			break;
		}
	}
					

Where optionsDialog is an AlertDialog. Add the following lines of code in the onCreate() method.

	AlertDialog.Builder builder = new AlertDialog.Builder(this);
	builder.setTitle("Choose an Option");
	builder.setItems(R.array.new_note_arr, dialogListener);
	optionsDialog = builder.create();
					

The item array comes from a static file. Create arrays.xml under res/values directory.

	<?xml version="1.0" encoding="utf-8"?>
	<resources>
		<string-array name="new_note_arr">
			<item>Note</item>
			<item>Checklist</item>
			<item>Snapshot</item>
		</string-array>
	</resources>			
					

We create dialogListener to handle on click events on each item.

	private DialogInterface.OnClickListener dialogListener = new DialogInterface.OnClickListener() {
		@Override
		public void onClick(DialogInterface dialog, int which) {
			if (dialog == optionsDialog) {
				Intent intent = new Intent();
				switch (which) {
				case 0:
					intent.setClass(BrowseActivity.this, BasicActivity.class);
					break;
				case 1:
					intent.setClass(BrowseActivity.this, ChecklistActivity.class);
					break;
				case 2:
					intent.setClass(BrowseActivity.this, SnapshotActivity.class);
					break;				
				}
				startActivity(intent);
			}
		}
	};
					

That's all we need to do to implement the dialog. Previously, we deferred implemention of onItemClick() method when a particular note is clicked in the ListView. We will do it now. Update the onItemClick() method as follows.

	@Override
	public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    	Note note = new Note(id);
    	note.load(SmartPad.db);
    	
    	Class claz = null;
    	String type = note.getType();
    	if (Note.BASIC.equals(type)) {
    		claz = BasicActivity.class;
    	} else if (Note.CHECKLIST.equals(type)) {
    		claz = ChecklistActivity.class;
    	} else if (Note.SNAPSHOT.equals(type)) {
    		claz = SnapshotActivity.class;
    	}

    	Intent intent = new Intent();
        intent.setClass(this, claz);
    	intent.putExtra(Note.COL_ID, id);
    	startActivity(intent);
	}
					

You must have noticed, we call show() on optionsDialog to display the dialog when the new note button is clicked. However, Android provides a neat way to manage dialogs when there are multiple dialogs in a screen. We will use this approach in the Manage tab.

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	@Override
	protected Dialog onCreateDialog(int id) {
		switch (id) {
		case DIALOG_NEW_CATEGORY:
			AlertDialog categoryDialog = new AlertDialog.Builder(this)
			   .setTitle("Enter Category Name")
			   .setView(categoryNameEdit)
			   .setCancelable(false)
			   .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
				   public void onClick(DialogInterface dialog, int id) {
					   // TODO persist new category
				   }
			   })
			   .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
				   public void onClick(DialogInterface dialog, int id) {
						dialog.cancel();
				   }
			   })
			   .create();		
	        return categoryDialog;
		}
		return super.onCreateDialog(id);
	}	
	
	@Override
	protected void onPrepareDialog(int id, Dialog dialog) {
		super.onPrepareDialog(id, dialog);
		
		switch (id) {
		case DIALOG_NEW_CATEGORY:
			break;
			
		case DIALOG_RENAME_CATEGORY:
			break;
		}		
	}
					

The onPrepareDialog() method is not required but is useful when some modification is to be done before showing the dialog. Here is how the dialog is shown.

	showDialog(DIALOG_NEW_CATEGORY);
					

We just pass the dialog id for the dialog that is to be shown.

11. The Context Menu

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Another useful thing is context menu which allows user to take action on a particular list item. Here is how it is implemented. The following line in onCreate() method registers the ListView for context menu,

	registerForContextMenu(noteList);
					

Next we need to override onCreateContextMenu() and onContextItemSelected() methods in Activity.

	@Override
	public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
		if (v.getId() == R.id.note_list) {
			getMenuInflater().inflate(R.menu.contextmenu_browse, menu);
			menu.setHeaderTitle("Choose an Option");
			menu.setHeaderIcon(R.drawable.ic_dialog_menu_generic);			
		}
	}

	@Override
	public boolean onContextItemSelected(MenuItem item) {
		AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
		
		switch (item.getItemId()) {
		case R.id.menu_edit:
			openNote(info.id, this);
			break;
			
		case R.id.menu_delete:
	    	Note note = new Note(info.id);
	    	note.delete(SmartPad.db);
	    	
	    	SimpleCursorAdapter adapter = (SimpleCursorAdapter) noteList.getAdapter();
	    	adapter.getCursor().requery();
	    	adapter.notifyDataSetChanged();	    	
			break;			
		}
		return true;
	}
					

We created a contextmenu_browse.xml file under res/menu to declare the menu items.

	<?xml version="1.0" encoding="utf-8"?>
	<menu xmlns:android="http://schemas.android.com/apk/res/android" >
		<item android:id="@+id/menu_edit" android:title="@string/edit" />
		<item android:id="@+id/menu_delete" android:title="@string/delete" />    
	</menu>			
					

The Manage tab also has context menu but there is a small difference since it need to be shown for a group item as well as a child item.

	@Override
	public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
		if (v.getId() == android.R.id.list) {
			ExpandableListView.ExpandableListContextMenuInfo info = (ExpandableListView.ExpandableListContextMenuInfo) menuInfo;
			int type = ExpandableListView.getPackedPositionType(info.packedPosition);
				
			getMenuInflater().inflate(R.menu.contextmenu_manage, menu);
			menu.setHeaderTitle("Choose an Option");
			menu.setHeaderIcon(R.drawable.ic_dialog_menu_generic);
			
			if (type == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
				// code specific to a child item
			} else if (type == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {
				// code specific to a group item
			}			
		}
	}

	@Override
	public boolean onContextItemSelected(MenuItem item) {
		ExpandableListView.ExpandableListContextMenuInfo info = (ExpandableListView.ExpandableListContextMenuInfo) item.getMenuInfo();
		int type = ExpandableListView.getPackedPositionType(info.packedPosition);

		if (type == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
			// code specific to a child item
		} else if (type == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {
			// code specific to a group item
		}

		switch (item.getItemId()) {
		case R.id.menu_edit:
			// TODO edit
			break;

		case R.id.menu_delete:
			// TODO delete
			break;			
		}
		
		SimpleCursorTreeAdapter adapter = (SimpleCursorTreeAdapter) getExpandableListAdapter();
		adapter.getCursor().requery();
		adapter.notifyDataSetChanged();
		
		return true;
	}
					

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In the next chapter we discuss how to implement the Settings screen using PreferenceActivity.

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