For notes about how SimpleAdapter and ListView work together to implement the List View, simpleadapter

For notes about how SimpleAdapter and ListView work together to implement the List View, simpleadapter

To use ListView, you need to add an adapter for it:

There are two types of adapters: 1. ArrayAdapter -- used for separate text display

2. SimpleAdapter -- used for text and Image Display

SimpleAdapter:

First look at the constructor of SimpleAdapter:

SimpleAdapter (context, data, resource, from,)

-- Context: context refers to the activity itself.

-- Data: data source: A List set containing map; each element in the List is a Map set, and Map contains multiple key-value pairs.

-- Resource: Layout file, which can be written by yourself. It can be obtained under R. Layout. The sum of the corresponding elements in the Layout can be stored in the Map.

-- From: a String [] array, which corresponds to the key element in the Map, similar to the initial name.

-- To: obtain the value of the corresponding key from the Map and store the specific value.

The following is an example.

Tool: Android studio

First, write the layout file: item. xml, which is stored in the layou folder.

　　

<?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="match_parent"    android:orientation="horizontal">    <ImageView        android:id="@+id/itempic"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_marginLeft="15dp"        android:src="@mipmap/ic_launcher" />    <TextView        android:id="@+id/itemtext"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="demo"        android:textSize="40sp" /></LinearLayout>

 

The instance in MainActivity receives ListView and SimpleAdapter objects.

Private ListView listView; // private ArrayAdapter <String> adapter; private SimpleAdapter si_adapter; // the list set is an abstract set that instantiates its instance object ArrayList private List <Map <String, object> simpleData; protected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); listView = (ListView) findViewById (R. id. listView); simpleData = new ArrayList <Map <String, Object> (); si_adapter = new SimpleAdapter (this, getData (), R. layout. item, new String [] {"pic", "text"}, new int [] {R. id. itempic, R. id. itemtext}); listView. setAdapter (si_adapter );}

The above getdate () method:

Public List <Map <String, Object> getData () {for (int I = 0; I <20; I ++) {Map <String, object> map = new HashMap <String, Object> ();
// Fill in the actual pic information map. put ("pic", R. mipmap. ic_launcher );
// Fill in the actual text information map. put ("text", "robot" + I + "); simpleData. add (map);} return simpleData ;}

Add the SimpleAdapter adapter to the ListView.

Analysis: SimpleAdapter's data parsing

Layout file: determines how data is presented in a view.

From: Specifies a specific symbol for each element.

To: The corresponding situation of each element in XML

Data: data source, used for parsing