ApiDemos 2.3研读笔记（2）

1、通过配置文件AndroidManifest.xml中可以看出ApiDemos的入口是ApiDemos.java。

<activity android:name="ApiDemos">      <intent-filter>          <action android:name="android.intent.action.MAIN" />          <category android:name="android.intent.category.DEFAULT" />          <category android:name="android.intent.category.LAUNCHER" />      </intent-filter></activity>

2、ApiDemos.java代码加上个人注释如下：

/** Copyright (C) 2007 The Android Open Source Project** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      [url]http://www.apache.org/licenses/LICENSE-2.0[/url]** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/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;/** 主要是通过对Activity的label信息进行分析，从而将Activity进行分类并通过ListView显示出来。* 例如<activity android:name=".app.HelloWorld" android:label="@string/activity_hello_world">的label为* App/Activity/Hello World，程序运行的结果是一级目录含有App选项，点击App出现的二级目录含有Activity选项，* 点击Activity出现的三级目录含有Hello World选项，点击Hello World会出现Hello World这个Activity运行的结果*/public class ApiDemos extends ListActivity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);                Intent intent = getIntent();        /*        * 当程序启动要显示一级目录（App, Content, ...）时，Intent对象里绑定的附加信息path为空        * 当点击一级目录选项进入二级目录（例如App下的Activity, Alarm, ...）时，path就不为空了（例如为App）        */        String path = intent.getStringExtra("com.example.android.apis.Path");                if (path == null) {            path = "";        }        // 通过adapter为当前ListActivity传递数据        setListAdapter(new SimpleAdapter(this, getData(path),                android.R.layout.simple_list_item_1, new String[] { "title" },                new int[] { android.R.id.text1 }));        // 允许当前ListView可以根据用户输入的值进行过滤        getListView().setTextFilterEnabled(true);    }    /*    * 获取应用列表，包括一级目录，二级目录，等等    */    protected List getData(String prefix) {        List<Map> myData = new ArrayList<Map>();        /*        * 获取在AndroidManifest.xml文件中的Intent Filter里配置了        * Intent.ACTION_MAIN和Intent.CATEGORY_SAMPLE_CODE的所有Activity        */        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);        mainIntent.addCategory(Intent.CATEGORY_SAMPLE_CODE);        PackageManager pm = getPackageManager();        List<ResolveInfo> list = pm.queryIntentActivities(mainIntent, 0);        if (null == list)            return myData;        String[] prefixPath;                // 当要显示一级目录时，prefix为空字符串；当点击App进入要显示二级目录时，prefix为App；        if (prefix.equals("")) {            prefixPath = null;        } else {            prefixPath = prefix.split("/");        }                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Activity的label信息，例如App/Activity/Hello World            CharSequence labelSeq = info.loadLabel(pm);            String label = labelSeq != null                    ? labelSeq.toString()                    : info.activityInfo.name;                        if (prefix.length() == 0 || label.startsWith(prefix)) {                // 例如labelPath = [App, Activity, Hello World]                String[] labelPath = label.split("/");                // 例如要显示一级目录时nextLabel = "App"，要显示二级目录时，nextLabel = "Activity"                String nextLabel = prefixPath == null ? labelPath[0] : labelPath[prefixPath.length];                // 当要显示的label为Activity而非目录时，需要为label绑定跳转到相关Activity的Intent                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);                    }                }            }        }        // 排序        Collections.sort(myData, sDisplayNameComparator);                return myData;    }    private final static Comparator<Map> sDisplayNameComparator = new Comparator<Map>() {        private final Collator  collator = Collator.getInstance();        public int compare(Map map1, Map map2) {            return collator.compare(map1.get("title"), map2.get("title"));        }    };    /*    * 为label绑定跳转到相关Activity的Intent    */    protected Intent activityIntent(String pkg, String componentName) {        Intent result = new Intent();        result.setClassName(pkg, componentName);        return result;    }        /*    * 为label绑定跳转到当前Activity的Intent，附加信息path为当前目录    * 例如为Activity这个label绑定的Intent中附加值为App/Activity    */    protected Intent browseIntent(String path) {        Intent result = new Intent();        result.setClass(this, ApiDemos.class);        result.putExtra("com.example.android.apis.Path", path);        return result;    }    /*    * 将符合条件的选项加入List中    */    protected void addItem(List<Map> 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 map = (Map) l.getItemAtPosition(position);        Intent intent = (Intent) map.get("intent");        startActivity(intent);    }}