ArrayAdapter详解：ArrayAdapter(Context context, int textViewResourceId, T[] objects)

末蓝、 2022-08-02 02:28 22阅读 0赞

## ArrayAdapter详解  ArrayAdapter(Context context, int textViewResourceId, T\[\] objects) ##

**【[尊重原创，转载请注明出处][Link 1]】http://blog.csdn.net/guyuealian/article/details/46790873**

**1、定义：android.widget.ArrayAdapter<T>**

ArrayAdapter常用6个构造方法： 
      ArrayAdapter(Context context, int textViewResourceId) 
      ArrayAdapter(Context context, int resource, inttextViewResourceId) 
      ArrayAdapter(Context context, inttextViewResourceId, T\[\] objects) 
      ArrayAdapter(Context context, int resource, inttextViewResourceId, T\[\] objects)         
      ArrayAdapter(Context context, inttextViewResourceId, List<T> objects) 
      ArrayAdapter(Context**context**, int**resource**, int**textViewResourceId**, List<T>**objects**)

**2、参数说明：**

**（1）context      ：** The current context.（传递Context对象，一般为this）  
**（2）resource   ：**  The id of the TextView within the layout resource to be populated：该布局资源在res/layout/Xxx.xml中定义后会自动在R.java文件中生成对应的ID，然后利用R.layout.Xxx调用即可，也可以使用系统已定义好的布局文件，比如：  
android.R.layout.simple\_list\_item\_1（前面必须加上android否则出错）  
android.R.layout.simple\_expandable\_list\_item\_1等等。  
注意：布局文件必须是关于TextView组件的XML文件（也可以TextView类的子类组件，如Button, CheckedTextView, Chronometer, DigitalClock, EditText, TextClock都是TextView的子类），列表项的每个条项都是按照这个TextView组件进行显示。

**（3）****textViewResourceId**： 对应的是resource布局文件中TextView组件的ID；  
**（4** **）objects     ：** The objects to represent in the ListView.数组或者List集合，用于为多个列表项提供数据

从中可知：textViewResourceId用于控制每个列表项的TextView组件（控制布局形式显示风格），而objects（数组或者List集合）为每个列表项的TextView组件提供显示数据。数组或者List集合有多少个元素，将会生成多少个列表项。

**3、 resource和textViewResourceId参数区别：**

一般来说，**resource**对应的是布局XML资源文件，而textViewResourceId指的是XML资源文件中textView组件的ID。问题来了，为什么ArrayAdapter构造方法都需要传入TextViewResourceId，有时不需要传入resource参数。**例如给构造方法ArrayAdapter<String>(Context context, int textViewResourceId, String\[\] objects)传入参数是这样的new ArrayAdapter<String>(this, R.layout.array\_item, arr1);**你会发现此时textViewResourceId传入的参数是**R.layout.array\_item不是组件****textView****的ID，而是布局文件的ID，Why****？？？？？？？**

**       **先来看看ArrayAdapter源码先！！！！！！！！你回惊奇的发现，ArrayAdapter的6个构造方法都调用了一个init()方法：

/**
 * Constructor
 *
 * @param context The current context.
 * @param textViewResourceId The resource ID for a layout file containing a TextView to use when
 * instantiating views.
 */
 public ArrayAdapter(Context context, int textViewResourceId) {
 init(context, textViewResourceId, 0, new ArrayList<T>());
 }
 
 /**
 * Constructor
 *
 * @param context The current context.
 * @param resource The resource ID for a layout file containing a layout to use when
 * instantiating views.
 * @param textViewResourceId The id of the TextView within the layout resource to be populated
 */
 public ArrayAdapter(Context context, int resource, int textViewResourceId) {
 init(context, resource, textViewResourceId, new ArrayList<T>());
 }
 
 /**
 * Constructor
 *
 * @param context The current context.
 * @param textViewResourceId The resource ID for a layout file containing a TextView to use when
 * instantiating views.
 * @param objects The objects to represent in the ListView.
 */
 public ArrayAdapter(Context context, int textViewResourceId, T[] objects) {
 init(context, textViewResourceId, 0, Arrays.asList(objects));
 }
 
 /**
 * Constructor
 *
 * @param context The current context.
 * @param resource The resource ID for a layout file containing a layout to use when
 * instantiating views.
 * @param textViewResourceId The id of the TextView within the layout resource to be populated
 * @param objects The objects to represent in the ListView.
 */
 public ArrayAdapter(Context context, int resource, int textViewResourceId, T[] objects) {
 init(context, resource, textViewResourceId, Arrays.asList(objects));
 }
 
 /**
 * Constructor
 *
 * @param context The current context.
 * @param textViewResourceId The resource ID for a layout file containing a TextView to use when
 * instantiating views.
 * @param objects The objects to represent in the ListView.
 */
 public ArrayAdapter(Context context, int textViewResourceId, List<T> objects) {
 init(context, textViewResourceId, 0, objects);
 }
 
 /**
 * Constructor
 *
 * @param context The current context.
 * @param resource The resource ID for a layout file containing a layout to use when
 * instantiating views.
 * @param textViewResourceId The id of the TextView within the layout resource to be populated
 * @param objects The objects to represent in the ListView.
 */
 public ArrayAdapter(Context context, int resource, int textViewResourceId, List<T> objects) {
 init(context, resource, textViewResourceId, objects);
 }

init()方法源码：

private void init(Context context, int resource, int textViewResourceId, List<T> objects) {
 mContext = context;
 mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
 mResource = mDropDownResource = resource;
 mObjects = objects;
 mFieldId = textViewResourceId;
 }

对比各个构造方法和init()的参数，你会发现init()第二个参数是resource是必须要传入的，也就是布局资源文件不可省略，而textViewResourceId默认是0。 当构造方法含有resource参数时，是布局资源文件的ID，且在实例化View时，该布局资源文件包含一个TextView 组件（The resource ID for a layout file containing a TextView to use when instantiating views.）；若省略resource参数时， 此时构造方法调用init()传入的第三个参数 默认设置为0。

因此：n**ew ArrayAdapter<String>****(this, R.layout.array\_item, arr1);等于new ArrayAdapter<String>(this, R.layout.array\_item,R.id.TextView ,arr1);，其中R.id.TextView是布局文件array\_item中的组件TextView的ID**

例子1：new ArrayAdapter<BookContent.Book>(getActivity(),android.R.layout.simple\_list\_item\_activated\_1,**android.R.id.text1**, arr))

这里第二个参数**resource：**android.R.layout.simple\_list\_item\_activated\_1，该布局文件是系统自定义好的TextView组件，其ID为@android:id/text1

<?xml version="1.0" encoding="utf-8"?>
 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@android:id/text1"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:textAppearance="?android:attr/textAppearanceListItemSmall"
 android:gravity="center_vertical"
 android:paddingStart="?android:attr/listPreferredItemPaddingStart"
 android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"
 android:background="?android:attr/activatedBackgroundIndicator"
 android:minHeight="?android:attr/listPreferredItemHeightSmall"
 />

第三个参数 **textViewResourceId：** android.R.id.text1，对应的是resource布局文件中TextView组件的ID，即text1

**例子2**

package org.crazyit.ui;
 
 import android.app.ListActivity;
 import android.os.Bundle;
 import android.widget.ArrayAdapter;
 
 /**
 * Description:
 * site: <a href="http://www.crazyit.org">crazyit.org</a>
 * Copyright (C), 2001-2014, Yeeku.H.Lee
 * This program is protected by copyright laws.
 * Program Name:
 * Date:
 * @author Yeeku.H.Lee kongyeeku@163.com
 * @version 1.0
 */
 public class ListActivityTest extends ListActivity
 {
 	@Override
 	public void onCreate(Bundle savedInstanceState)
 	{
 		super.onCreate(savedInstanceState);
 		// 无需使用布局文件
 		String[] arr = { "孙悟空", "猪八戒", "唐僧" };
 		// 创建ArrayAdapter对象
 		ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
 			android.R.layout.simple_list_item_multiple_choice, arr);
 		// 设置该窗口显示列表
 		setListAdapter(adapter);
 	}
 }

[Link 1]: http://blog.csdn.net/guyuealian/article/details/46790873