ApiDemos示例学习（1）——ApiDemos示例的导入

 package com.example.android.apis;

 import android.app.ListActivity;

 import android.content.Intent;

 import android.content.pm.PackageManager;

 import android.content.pm.ResolveInfo;

 import android.os.Bundle;

 import android.view.View;

 import android.widget.ListView;

 import android.widget.SimpleAdapter;

 import java.text.Collator;

 import java.util.ArrayList;

 import java.util.Collections;

 import java.util.Comparator;

 import java.util.HashMap;

 import java.util.List;

 import java.util.Map;

 public class ApiDemos extends ListActivity {

     @Override

     public void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         Intent intent = getIntent();

         String path = intent.getStringExtra("com.example.android.apis.Path");

         if (path == null) {

             path = "";

         }

         setListAdapter(new SimpleAdapter(this, getData(path),

                 android.R.layout.simple_list_item_1, new String[] { "title" },

                 new int[] { android.R.id.text1 }));

         getListView().setTextFilterEnabled(true);

     }

     protected List<Map<String, Object>> getData(String prefix) {

         List<Map<String, Object>> myData = new ArrayList<Map<String, Object>>();

         Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);

         mainIntent.addCategory(Intent.CATEGORY_SAMPLE_CODE);

         //通过PackageManager从AndroidManifest.xml中读取所有含有Intent.ACTION_MAIN

         //和Intent.CATEGORY_SAMPLE_CODE的所有Activity信息

         PackageManager pm = getPackageManager();

         List<ResolveInfo> list = pm.queryIntentActivities(mainIntent, 0);

         if (null == list)

             return myData;

         String[] prefixPath;

         String prefixWithSlash = prefix;

         if (prefix.equals("")) {

             prefixPath = null;

         } else {

             prefixPath = prefix.split("/");

             prefixWithSlash = prefix + "/";

         }

         //变量len 记录了满足条件的Activity个数

         int len = list.size();

         Map<String, Boolean> entries = new HashMap<String, Boolean>();

         for (int i = 0; i < len; i++) {

             ResolveInfo info = list.get(i);//获取对应activity的ResolveInfo信息

             CharSequence labelSeq = info.loadLabel(pm);//获取对应activity的android:label属性值

             //如果为空，则label初始化为activity对应的android:name属性值，否则直接转换为string赋值给label

             String label = labelSeq != null

                     ? labelSeq.toString()

                     : info.activityInfo.name;//anctivityInfo.name对应于属性android:name

             if (prefixWithSlash.length() == 0 || label.startsWith(prefixWithSlash)) {

                 String[] labelPath = label.split("/");

                 //prefixPath为空时，nextLabel值为labelPath第一个字符串；否则为labelPath中索引为prefixPath长度的值，不会造成越界因为

                 //prefixPath的最大长度永远比labelPath最大长度小1

                 String nextLabel = prefixPath == null ? labelPath[0] : labelPath[prefixPath.length];

                 if ((prefixPath != null ? prefixPath.length : 0) == labelPath.length - 1) {

                     addItem(myData, nextLabel, activityIntent(

                             info.activityInfo.applicationInfo.packageName,

                             info.activityInfo.name));

                 } else {

                     if (entries.get(nextLabel) == null) {

                         addItem(myData, nextLabel, browseIntent(prefix.equals("") ? nextLabel : prefix + "/" + nextLabel));

                         entries.put(nextLabel, true);

                     }

                 }

             }

         }

         Collections.sort(myData, sDisplayNameComparator);

         return myData;

     }

     private final static Comparator<Map<String, Object>> sDisplayNameComparator =

         new Comparator<Map<String, Object>>() {

         private final Collator   collator = Collator.getInstance();

         public int compare(Map<String, Object> map1, Map<String, Object> map2) {

             return collator.compare(map1.get("title"), map2.get("title"));

         }

     };

     //叶子列表项对应的Intent

     protected Intent activityIntent(String pkg, String componentName) {

         Intent result = new Intent();

         result.setClassName(pkg, componentName);

         return result;

     }

     //分类列表项对应的Intent

     protected Intent browseIntent(String path) {

         Intent result = new Intent();

         result.setClass(this, ApiDemos.class);

         result.putExtra("com.example.android.apis.Path", path);

         return result;

     }

     protected void addItem(List<Map<String, Object>> data, String name, Intent intent) {

         Map<String, Object> temp = new HashMap<String, Object>();

         temp.put("title", name);

         temp.put("intent", intent);

         data.add(temp);

     }

     @Override

     protected void onListItemClick(ListView l, View v, int position, long id) {

         Map<String, Object> map = (Map<String, Object>)l.getItemAtPosition(position);

         Intent intent = (Intent) map.get("intent");

         startActivity(intent);

     }

 }