51. SimpleAdapter, adding and deleting records

In this lesson:

- use SimpleAdapter to build a list
- add and delete entries in the list

How to display data in the list using the SimpleAdapter we know. Now we will try to change this data. Make a list with the ability to delete and add entries. We will add the button and delete using the context menu.

Create a project:

Project name : P0511_SimpleAdapterData
Build Target : Android 2.3.3
Application name : SimpleAdapterData
Package name : ru.startandroid.develop.p0511simpleadapterdata
Create Activity : MainActivity

Screen main.xml :

  <? xml version = "1.0" encoding = "utf-8"?> 
  <LinearLayout 
  xmlns: android = "http://schemas.android.com/apk/res/android" 
  android: layout_width = "fill_parent" 
  android: layout_height = "fill_parent" 
  android: orientation = "vertical"> 
  <Button 
  android: layout_width = "wrap_content" 
  android: layout_height = "wrap_content" 
  android: onClick = "onButtonClick" 
  android: text = "Add post"> 
  </ Button> 
  <ListView 
  android: id = "@ + id / lvSimple" 
  android: layout_width = "match_parent" 
  android: layout_height = "wrap_content"> 
  </ Listview> 
  </ LinearLayout> 

Button to add and list. From interesting things you can note the onClick property of the button. Then it becomes clear what it is.

Layout for item list item.xml :

  <? xml version = "1.0" encoding = "utf-8"?> 
  <LinearLayout 
  xmlns: android = "http://schemas.android.com/apk/res/android" 
  android: layout_width = "match_parent" 
  android: layout_height = "wrap_content" 
  android: orientation = "horizontal"> 
  <ImageView 
  android: id = "@ + id / ivImg" 
  android: layout_width = "wrap_content" 
  android: layout_height = "wrap_content" 
  android: src = "@ drawable / ic_launcher"> 
  </ ImageView> 
  <Textview 
  android: id = "@ + id / tvText" 
  android: layout_width = "wrap_content" 
  android: layout_height = "wrap_content" 
  android: layout_gravity = "center_vertical" 
  android: layout_marginLeft = "10dp" 
  android: text = "" 
  android: textSize = "18sp"> 
  </ TextView> 
  </ LinearLayout> 

Picture and text.

MainActivity.java code:

In the onCreate method , we create a collection of Map objects, matching arrays, create an adapter and a list, add the option of the context menu for the list.

The onButtonClick method - we specified it in main.xml in the onClick property of the button. And now when you click on the button, this method will be executed. A separate click handler is not needed.

In this method, we create a new Map, add it to the data collection and inform that the data has changed and we need to update the list.

The onCreateContextMenu method creates a context menu. We create only one item - to delete the record.

In onContextItemSelected, we process the click on the context menu item. When you call the context menu, the object for which it was called, transfers information about itself to the menu. To get data on a list item for which the context menu call was made, we use the getMenuInfo method. The AdapterContextMenuInfo object contains data about the View, id and position of the list item. We use the position to remove the corresponding Map from the collection. After that we inform that the data has changed.

All save and run.

The screenshot shows the context menu, which is invoked with a long press on the list item. Behind it is a list and a button to add entries.

Entries are added and deleted. Editing I did not do. There is the same principle. Get the Map and change its attributes.

From the code it is clear that to update the list, you need to change the data used by the adapter and call its notification method.

In the next lesson:

- use SimpleCursorAdapter to build a list
- add and delete entries in the list