Android 实例解说Application类-手机开发-火龙果软件工程

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Android 实例解说Application类

作者 WPJY_521的博客，火龙果软件发布于 2014-04-23

何为Application，有何用途？Google官方文档是这样说的：维护全局应用程序的状态，使用的时候继承于它创建一个子类即可，同时在AndroidManifest.xml文件的<application> 标签的name属性制定它的名字，也就是子类名称。当应用程序的包被创建的时候这个类就会被实例化，而且它的生命周期和应用程序是一样的。不过Google在下面的提示中也说道大多数情况下不需要使用这个类，因为如果应用程序使用了单例模式的话，效果和Application提供的事一样的，而且也更加容易控制、规范。

关于Application类有以下公开方法：

其中最常用的就是onCreaet()、onTerminate()以及onLowMemory()方法，onCreaet()它会在这个类实例化的时候调用（这个地方需要十分注意，它只会在程序第一次启动的时候调用，不是每次都调用，因为Application类会在创建包的时候初始化），onTerminate()会在app关闭的时候调用，onLowMemory()是在内存过低的情况下调用的。那onTerminate()是干什么用的呢？网上介绍说是在程序终结的时候调用，从下面的实例中也是这样用的。不过在Google的开发文档以及很多书籍对这个类的用法很少提及，但实际开发情况是如何的呢。不妨反编译几个常用的app一看究竟，因为涉及到一些因素就不方便说是哪个app，以代号表明。

1、app_1

先把代码贴出来，因为这个app的Application的实现比较简单，就先拿出来说。

import android.annotation.TargetApi;
import android.app.Application;
import android.content.Context;
import android.os.Build.VERSION;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration.Builder;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;
import java.io.PrintStream;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpProtocolParams;
public class MyApplication
  extends Application
{
  private HttpClient httpClient;
  public boolean isLogin = false;
 
  private HttpClient createHttpClient()
  {
    BasicHttpParams localBasicHttpParams = new BasicHttpParams();
    HttpProtocolParams.setVersion(localBasicHttpParams, HttpVersion.HTTP_1_1);
    HttpProtocolParams.setContentCharset(localBasicHttpParams, "ISO-8859-1");
    HttpProtocolParams.setUseExpectContinue(localBasicHttpParams, true);
    HttpConnectionParams.setConnectionTimeout(localBasicHttpParams, 20000);
    HttpConnectionParams.setSoTimeout(localBasicHttpParams, 20000);
    HttpConnectionParams.setSocketBufferSize(localBasicHttpParams, 8192);
    SchemeRegistry localSchemeRegistry = new SchemeRegistry();
    localSchemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
    localSchemeRegistry.register(new Scheme("https", SSLSocketFactory.getSocketFactory(), 443));
    return new DefaultHttpClient(new ThreadSafeClientConnManager
(localBasicHttpParams, localSchemeRegistry), localBasicHttpParams);
  }
 
  public static void initImageLoader(Context paramContext)
  {
    ImageLoaderConfiguration localImageLoaderConfiguration = new ImageLoaderConfiguration.Builder(paramContext).
threadPriority(3).denyCacheImageMultipleSizesInMemory().discCacheFileNameGenerator(new Md5FileNameGenerator()).
tasksProcessingOrder(QueueProcessingType.LIFO).writeDebugLogs().build();
    ImageLoader.getInstance().init(localImageLoaderConfiguration);
  }
 
  private void shutdownHttpClient()
  {
    if ((this.httpClient != null) && (this.httpClient.getConnectionManager() != null)) {
      this.httpClient.getConnectionManager().shutdown();
    }
  }
 
  public HttpClient getHttpClient()
  {
    return this.httpClient;
  }
 
  @TargetApi(9)
  public void onCreate()
  {
    super.onCreate();
    this.httpClient = createHttpClient();
    System.out.println(Build.VERSION.SDK_INT);
    initImageLoader(getApplicationContext());
  }
 
  public void onLowMemory()
  {
    super.onLowMemory();
    shutdownHttpClient();
  }
 
  public void onTerminate()
  {
    super.onTerminate();
    shutdownHttpClient();
  }
 
  public static class Config
  {
    public static final boolean DEVELOPER_MODE;
  }
}

从import导入的包就可以看出来，在这个类里面使用了强大的universalimageloader异步加载图片以及使用的apache的HttpClient。然后整体看一下这个类，发现它不仅重载了 onCreate()方法，还重载了onLowMemory()以及onTerminate()方法。onLowMemory()顾名思义就是在Android系统内存低的情况下调用的，可以在这个方法里面做一下释放内存的功能。

那就从onCreate()方法开始，里面代码如下：

  this.httpClient = createHttpClient();
  System.out.println(Build.VERSION.SDK_INT);
  initImageLoader(getApplicationContext());

第一个方法，创建httpClient 的对象，至于方法的具体细节就不介绍了，不是本文讨论重点，下同。第二个方法就是初始化universalimageloader了。总体来说这个app的Application的实现还是比较简单的，也比较容易理解。接下来介绍一个稍微复杂一点的。

2、app_2

import android.app.Application;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.widget.Toast;
import com.baidu.mapapi.BMapManager;
import com.baidu.mapapi.MKGeneralListener;
import com.baidu.mapapi.MKLocationManager;
import java.io.File;
public class App
  extends Application
{
  public static App app;
  public static boolean hideOtherExchanges = false;
  public static boolean hideUpdateNotice = false;
  public BMapManager mBMapMan = null;
  public String mStrKey = "4BFEB7A7F3E7CD4B0FBAE61BABD11F1E11D7EAC8";
 
  public static void delete(File paramFile)
  {
    if (paramFile.isFile()) {
      paramFile.delete();
    }
    while (!paramFile.isDirectory()) {
      return;
    }
    File[] arrayOfFile = paramFile.listFiles();
    if ((arrayOfFile == null) || (arrayOfFile.length == 0))
    {
      paramFile.delete();
      return;
    }
    for (int i = 0;; i++)
    {
      if (i >= arrayOfFile.length)
      {
        paramFile.delete();
        return;
      }
      delete(arrayOfFile[i]);
    }
  }
 
  public boolean init()
  {
    this.mBMapMan = new BMapManager(this);
    return this.mBMapMan.init(this.mStrKey, new MyGeneralListener());
  }
 
  public void onCreate()
  {
    app = this;
    if (init()) {
      this.mBMapMan.getLocationManager().setNotifyInternal(10, 5);
    }
    super.onCreate();
    try
    {
      localBundle = getPackageManager().getApplicationInfo(getPackageName(), 128).metaData;
      str2 = localBundle.getString("UMENG_CHANNEL");
      arrayOfString1 = localBundle.getString("HIDE_OTHER_EXCHANGE_APK_CHANNEL").split(",");
      i = 0;
    }
    catch (Exception localException1)
    {
      for (;;)
      {
        Bundle localBundle;
        String str2;
        String[] arrayOfString1;
        int i;
        String[] arrayOfString2;
        int j;
        Logger.w(localException1);
        continue;
        i++;
        continue;
        label303:
        if (arrayOfString2[j].equals(str2)) {
          hideUpdateNotice = true;
        } else {
          j++;
        }
      }
    }
    if (i >= arrayOfString1.length) {}
    for (;;)
    {
      arrayOfString2 = localBundle.getString("HIDE_DOUGUO_UPDATE_NOTICE").split(",");
      j = 0;
      int k = arrayOfString2.length;
      if (j < k) {
        break label303;
      }
      WeiboHelper.setConfig(app);
      RenrenHelper.setConfig(app);
      DouguoWebAPI.setConfig(app);
      Logger.setConfig(app);
      Thread.setDefaultUncaughtExceptionHandler(new ExceptionHandler(getApplicationContext()));
      try
      {
        String str1 = Environment.getExternalStorageDirectory().getAbsolutePath() + "/douguo/" + getPackageName();
        File localFile1 = new File(str1);
        File localFile2 = localFile1.getParentFile();
        if (!localFile2.exists()) {
          localFile2.mkdir();
        }
        if (!localFile1.exists()) {
          localFile1.mkdir();
        }
        File localFile3 = new File(str1 + "/.nomedia");
        if (!localFile3.exists()) {
          localFile3.createNewFile();
        }
        return;
      }
      catch (Exception localException2)
      {
        Logger.w(localException2);
      }
      if (!arrayOfString1[i].equals(str2)) {
        break;
      }
      hideOtherExchanges = true;
    }
  }
 
  public void onLowMemory()
  {
    super.onLowMemory();
    Logger.e("!!!!!!!!!!!!!!onLowMemory!!!!!!!!!!!!");
  }
 
  public void onTerminate()
  {
    if (this.mBMapMan != null)
    {
      this.mBMapMan.destroy();
      this.mBMapMan = null;
    }
    super.onTerminate();
    new Thread()
    {
      public void run()
      {
        App.delete(new File(Environment.getExternalStorageDirectory() + "/douguo/yummyDiary/"));
      }
    }.start();
  }
 
  static class MyGeneralListener
    implements MKGeneralListener
  {
    public void onGetNetworkState(int paramInt)
    {
      Toast.makeText(App.app.getApplicationContext(), "您的网络出错啦！", 1).show();
    }
   
    public void onGetPermissionState(int paramInt) {}
  }
}

这个类有两个自定义的方法，一个是delete(File paramFile)，用于删除指定文件，一个是 init()，用于初始化百度地图以及网络连接。进入onCreate()方法，首选是给变量app实例化。接着调用init()方法进行判断，如果在init()方法返回true，说明有网络连接正常并且已经初始化完毕百度地图，之后会不断发送tNotify通知。然后进入try catch方法里面，由于反编译的问题，有些语句反编译完毕后就是现在这个样子。至于如何解读，以后会介绍，现在不是重点。看一下，在try里面是初始化了友盟的一些东西，然后再catch里面声明了一些变量，并且根据某些条件创建或者删除指定的文件。最后就是onTerminate()方法，可以看到在这个方法里面它销毁了百度地图、删除了一些程序的文件等。

3、app_3

import android.app.ActivityManager;
import android.app.ActivityManager.RunningAppProcessInfo;
import android.app.Application;
import android.content.Context;
import android.os.Process;
import com.baidu.android.silentupdate.SilentManager;
import java.util.Iterator;
import java.util.List;
public class FrontiaApplication
  extends Application
{
  private static final String a =
 "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCYAFbG0oYmKgh6o7BhZIHf1njBpZXqyWBnYz2ip3Wp
+s97OeA/pTe8xebuGJHwq4xbsGQrJWepIbUVrdjm6JRmdvuJhar7/
hC/UNnUkJgYdYl10OZKlvcFFgK3V7XGBPplXldDnhbgscna3JG8U3025WSxZCP5vy/8cfxsEoVx5QIDAQAB";
 
  public static void initFrontiaApplication(Context paramContext)
  {
    SilentManager.setKey
("MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCYAFbG0oYmKgh6o7BhZIHf1njBpZXqyWBnYz2ip3Wp+
s97OeA/pTe8xebuGJHwq4xbsGQrJWepIbUVrdjm6JRmdvuJhar7/
hC/UNnUkJgYdYl10OZKlvcFFgK3V7XGBPplXldDnhbgscna3JG8U3025WSxZCP5vy/8cfxsEoVx5QIDAQAB");
    SilentManager.enableRSA(false);
    SilentManager.loadLib(paramContext.getApplicationContext(), "frontia_plugin", "plugin-deploy.jar");
  }
 
  public void onCreate()
  {
    super.onCreate();
    ActivityManager localActivityManager = (ActivityManager)getSystemService("activity");
    int i = Process.myPid();
    Iterator localIterator = localActivityManager.getRunningAppProcesses().iterator();
    while (localIterator.hasNext())
    {
      ActivityManager.RunningAppProcessInfo localRunningAppProcessInfo =
 (ActivityManager.RunningAppProcessInfo)localIterator.next();
      if ((localRunningAppProcessInfo.pid == i) &&
 (!localRunningAppProcessInfo.processName.endsWith(getPackageName()))) {
        initFrontiaApplication(getApplicationContext());
      }
    }
  }
}
import android.content.Context;
import com.baidu.frontia.FrontiaApplication;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration.Builder;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;
public class UILApplication
  extends FrontiaApplication
{
  public static void initImageLoader(Context paramContext)
  {
    ImageLoaderConfiguration localImageLoaderConfiguration =
 new ImageLoaderConfiguration.Builder(paramContext).threadPriority(3).denyCacheImageMultipleSizesInMemory().
discCacheFileNameGenerator(new Md5FileNameGenerator()).tasksProcessingOrder(QueueProcessingType.LIFO).build();
    ImageLoader.getInstance().init(localImageLoaderConfiguration);
  }
 
  public void onCreate()
  {
    com.nostra13.universalimageloader.utils.StorageUtils.basePath = "Meishi";
    com.nostra13.universalimageloader.utils.StorageUtils.childPath = "Temp";
    com.nostra13.universalimageloader.utils.StorageUtils.childImgName = "imgs";
    super.onCreate();
    CrashHandler.getInstance().init(this);
    initImageLoader(getApplicationContext());
  }
}

这个app的Application的实现比较特殊一点，使用了两个类，在第一个类的onCreate()方法里面主要是先是获取所有的进程，然后迭代进行判断，如果满足条件则调用initFrontiaApplication()方法用来设置key。第二个类则用于初始化universalimageloader。其实觉得没有必要分开来操作，写在一个Application类里面即可。

4、app_4

import android.app.Application;
import android.graphics.Bitmap.Config;
import android.text.TextUtils;
import android.webkit.CookieManager;
import android.webkit.CookieSyncManager;
import cn.jpush.android.api.BasicPushNotificationBuilder;
import cn.jpush.android.api.JPushInterface;
import com.baidu.location.BDLocation;
import com.baidu.location.LocationClient;
import com.baidu.location.LocationClientOption;
import com.baidu.mapapi.BMapManager;
import com.baidu.mapapi.MKGeneralListener;
import com.nostra13.universalimageloader.cache.memory.impl.WeakMemoryCache;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.DisplayImageOptions.Builder;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration.Builder;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
import com.nostra13.universalimageloader.core.display.RoundedBitmapDisplayer;
import java.util.Calendar;
import java.util.Date;

public class AzkApp
  extends Application
{
  public static final String BASEURL = Api.BASE_URL;
  public static DisplayImageOptions avatarOptions;
  public static DisplayImageOptions defaultOptions;
  private static AzkApp instance;
  private static boolean jpushInitied;
  public static DisplayImageOptions noStubOptions;
  private final String COOKIEURL = "http://aimeiwei.me";
  public BDLocation bdLocation;
  private CookieManager cookieManager;
  private CookieSyncManager cookieSyncManager;
  public BMapManager mBMapMan;
  public LocationClient mLocationClient;
  public int mapCount;
  private String nickname = "";
  private String password = "";
  private String username = "";
 
  private String getBaiduKey()
  {
    return AzkHelper.getMetaData(getApplicationContext(), "BAIDU_KEY");
  }
 
  public static AzkApp getInstance()
  {
    return instance;
  }
 
  private void initCookieManager()
  {
    this.cookieSyncManager = CookieSyncManager.createInstance(this);
    this.cookieManager = CookieManager.getInstance();
    this.cookieManager.setAcceptCookie(true);
    if (isLogin())
    {
      String str = this.cookieManager.getCookie("http://aimeiwei.me");
      if ((str == null) || (!str.contains("username")) || (!str.contains("password")))
      {
        AzkHelper.showLog("初始化cookie");
        setCookie(this.username, this.password);
      }
    }
    showCookie();
  }
 
  private void initHttp()
  {
    AzkHelper.showLog("httpClient初始化");
    Http.initHttp(AzkHelper.sAzkUserAgent);
    Http.setBaseUrl(Api.API_URL);
    if ((!TextUtils.isEmpty(this.username)) && (!TextUtils.isEmpty(this.password))) {
      Http.setUser(this.username, this.password);
    }
  }
 
  private void initImageLoader()
  {
    AzkHelper.showLog("ImageLoader图片加载器初始化");
    long l1 = Runtime.getRuntime().maxMemory();
    long l2 = l1 / 1024L / 1024L;
    AzkHelper.showLog("maxHeap: " + l2);
    int i = (int)l1 / 4;
    DisplayImageOptions.Builder localBuilder1 = new DisplayImageOptions.Builder();
    DisplayImageOptions.Builder localBuilder2 = localBuilder1.showImageOnLoading(2130837835);
    Bitmap.Config localConfig;
    ImageScaleType localImageScaleType;
    label103:
    int j;
    label188:
    ImageLoaderConfiguration.Builder localBuilder6;
    if (l2 >= 256L)
    {
      localConfig = Bitmap.Config.ARGB_8888;
      DisplayImageOptions.Builder localBuilder3 = localBuilder2.bitmapConfig(localConfig);
      if (l2 < 256L) {
        break label283;
      }
      localImageScaleType = ImageScaleType.IN_SAMPLE_POWER_OF_2;
      localBuilder3.imageScaleType(localImageScaleType).cacheInMemory(true).cacheOnDisc(true);
      defaultOptions = localBuilder1.build();
      DisplayImageOptions.Builder localBuilder4 = new DisplayImageOptions.Builder();
      localBuilder4.cacheInMemory(true).cacheOnDisc(true);
      noStubOptions = localBuilder4.build();
      ImageLoaderConfiguration.Builder localBuilder5 =
 new ImageLoaderConfiguration.Builder(getApplicationContext()).
memoryCacheExtraOptions(Constants.IMAGE_SIZE, Constants.IMAGE_SIZE);
      if (l2 < 256L) {
        break label291;
      }
      j = 1;
      localBuilder6 = localBuilder5.threadPriority(5 - j);
      if (l2 < 256L) {
        break label297;
      }
    }
    label283:
    label291:
    label297:
    for (int k = 3;; k = 2)
    {
      ImageLoaderConfiguration localImageLoaderConfiguration =
 localBuilder6.threadPoolSize(k).memoryCacheSize(i).memoryCache(new WeakMemoryCache()).
denyCacheImageMultipleSizesInMemory().defaultDisplayImageOptions(defaultOptions).build();
      ImageLoader.getInstance().init(localImageLoaderConfiguration);
      avatarOptions = localBuilder1.displayer(new RoundedBitmapDisplayer(8)).build();
      return;
      localConfig = Bitmap.Config.RGB_565;
      break;
      localImageScaleType = ImageScaleType.IN_SAMPLE_INT;
      break label103;
      j = 2;
      break label188;
    }
  }
 
  private void removeCookie()
  {
    this.cookieManager.removeSessionCookie();
    this.cookieManager.removeAllCookie();
    this.cookieSyncManager.sync();
  }
 
  private void setCookie(String paramString1, String paramString2)
  {
    Calendar localCalendar = Calendar.getInstance();
    localCalendar.set(2025, 11, 29);
    String str = localCalendar.getTime().toString();
    this.cookieManager.setCookie("http://aimeiwei.me", "username=" + paramString1 + "; path=/; expires=" + str);
    this.cookieManager.setCookie("http://aimeiwei.me", "password=" + paramString2 + "; path=/; expires=" + str);
    this.cookieSyncManager.sync();
    showCookie();
  }
 
  private void setJpushAlias()
  {
    AzkHelper.showLog("jpush", "username: " + this.username);
    JPushInterface.setAliasAndTags(this, this.username, null);
  }
 
  private void showCookie()
  {
    String str = this.cookieManager.getCookie("http://aimeiwei.me");
    AzkHelper.showLog("cookie:" + str);
  }
 
  public String getNickname()
  {
    return this.nickname;
  }
 
  public String getPassword()
  {
    return this.password;
  }
 
  public String getUsername()
  {
    return this.username;
  }
 
  public void initBMapManager()
  {
    if (this.mBMapMan == null)
    {
      this.mBMapMan = new BMapManager(this);
      String str = getBaiduKey();
      AzkHelper.showLog("初始化BMapManager, BAIDU_KEY: " + str);
      this.mBMapMan.init(str, new MKGeneralListener()
      {
        public void onGetNetworkState(int paramAnonymousInt)
        {
          if (paramAnonymousInt == 2) {
            AzkHelper.showErrorLog("您的网络出错啦！");
          }
        }
       
        public void onGetPermissionState(int paramAnonymousInt)
        {
          if (paramAnonymousInt == 300) {
            AzkHelper.showLog("请输入正确的百度授权Key");
          }
        }
      });
    }
  }
 
  public void initJpush()
  {
    if (jpushInitied) {
      return;
    }
    AzkHelper.showLog("极光推送初始化");
    AzkHelper.showLog("jpush", "极光推送初始化");
    JPushInterface.init(this);
    BasicPushNotificationBuilder localBasicPushNotificationBuilder = new BasicPushNotificationBuilder(this);
    localBasicPushNotificationBuilder.statusBarDrawable = 2130837777;
    JPushInterface.setPushNotificationBuilder(Integer.valueOf(1), localBasicPushNotificationBuilder);
    if (!TextUtils.isEmpty(this.username)) {
      setJpushAlias();
    }
    jpushInitied = true;
  }
 
  public void initMap()
  {
    AzkHelper.showLog("百度地图初始化");
    this.mLocationClient = new LocationClient(this);
    LocationClientOption localLocationClientOption = new LocationClientOption();
    localLocationClientOption.setProdName(getString(2131296262));
    localLocationClientOption.setOpenGps(true);
    localLocationClientOption.setPriority(2);
    localLocationClientOption.setAddrType("all");
    localLocationClientOption.setCoorType("gcj02");
    this.mLocationClient.setLocOption(localLocationClientOption);
    this.mLocationClient.setAK(getBaiduKey());
    initBMapManager();
  }
 
  public boolean isLogin()
  {
    boolean bool = true;
    if ((TextUtils.isEmpty(this.username)) || (TextUtils.isEmpty(this.password))) {
      bool = false;
    }
    return bool;
  }
 
  public boolean isYourself(User paramUser)
  {
    if ((TextUtils.isEmpty(this.username)) || (paramUser == null)) {
      return false;
    }
    return this.username.equals(paramUser.getId());
  }
 
  public boolean isYourself(UserNew paramUserNew)
  {
    if ((TextUtils.isEmpty(this.username)) || (paramUserNew == null)) {
      return false;
    }
    return this.username.equals(paramUserNew.getId());
  }
 
  public void onCreate()
  {
    AzkHelper.showLog("Application Aimeiwei onCreate");
    super.onCreate();
    instance = this;
    AzkHelper.prepareUserAgent(this);
    this.username = AzkHelper.getStringPref(this, "username");
    this.password = AzkHelper.getStringPref(this, "password");
    this.nickname = AzkHelper.getStringPref(this, "nickname");
    AzkHelper.showLog("BuildConfig.DEBUG: false");
    AzkHelper.closeLog();
    initHttp();
    initImageLoader();
    initJpush();
    initMap();
    initCookieManager();
  }
 
  public void onLowMemory()
  {
    AzkHelper.showLog("onLowMemory");
    super.onLowMemory();
  }
 
  public void onTerminate()
  {
    instance = null;
    if (this.mBMapMan != null)
    {
      this.mBMapMan.destroy();
      this.mBMapMan = null;
    }
    super.onTerminate();
  }
 
  public void removeUser()
  {
    Http.clearUser();
    AzkHelper.removePref(this, "username");
    AzkHelper.removePref(this, "password");
    AzkHelper.removePref(this, "nickname");
    this.username = "";
    this.password = "";
    this.nickname = "";
    AccessTokenKeeper.clear(getApplicationContext());
    removeCookie();
  }
 
  public void removeUser2()
  {
    Http.clearUser();
    AzkHelper.removePref(this, "username");
    AzkHelper.removePref(this, "password");
    AzkHelper.removePref(this, "nickname");
    this.password = "";
    this.nickname = "";
    AccessTokenKeeper.clear(getApplicationContext());
    AccessTokenKeeperForQQ.clear(getApplicationContext());
    removeCookie();
  }
 
  public void setNickname(String paramString)
  {
    AzkHelper.setStringPref(this, "nickname", paramString);
    this.nickname = paramString;
  }
 
  public void setPassword(String paramString)
  {
    AzkHelper.setStringPref(this, "password", paramString);
    this.password = paramString;
  }
 
  public void setUser(String paramString1, String paramString2)
  {
    setUserName(paramString1);
    setPassword(paramString2);
    Http.setUser(paramString1, paramString2);
  }
 
  public void setUser(String paramString1, String paramString2, String paramString3)
  {
    setNickname(paramString3);
    setUser(paramString1, paramString2);
    setCookie(paramString1, paramString2);
  }
 
  public void setUserName(String paramString)
  {
    AzkHelper.setStringPref(this, "username", paramString);
    this.username = paramString;
    setJpushAlias();
  }
}

这个app的实现相对来说还是比较复杂的，但是无非就是初始化一些信息。从import导包可以看到，使用了极光推送、百度地图以及universalimageloader，所以按照之前的分析经验之后一定会在onCreate()方法里面去初始化这些功能的。看一下onCreate()方法：

  public void onCreate()
  {
    AzkHelper.showLog("Application Aimeiwei onCreate");
    super.onCreate();
    instance = this;
    AzkHelper.prepareUserAgent(this);
    this.username = AzkHelper.getStringPref(this, "username");
    this.password = AzkHelper.getStringPref(this, "password");
    this.nickname = AzkHelper.getStringPref(this, "nickname");
    AzkHelper.showLog("BuildConfig.DEBUG: false");
    AzkHelper.closeLog();
    initHttp();
    initImageLoader();
    initJpush();
    initMap();
    initCookieManager();
  }

很清晰明了，从方法名称也可以看出来，就是初始化各种功能。至于具体方法的实现，不多做介绍，感兴趣可以自己去研究。
最后总结一下，上面例举了四个市场上的app程序的Application类的实现。从中可以发现，在Application类的实现类中，无非就是做一些初始化程序数据、检查运行环境、销毁数据等。

1、初始化程序数据：

常用的初始化的手段有创建程序所需要的目录，设置开发平台的key，初始化地图信息，初始化http或者其他和网络有关的东西，初始化推送等等。

2、检查运行环境

比如检查是否存在sd卡、判断网络连接状况、检查内存等等。

3、销毁数据

就是在onTerminate()方法里面销毁之前使用到的一些东西。说到onTerminate()这个方法，在官方文档中是这样说的，
This method is for use in emulated process environments. It will never be called on a production Android device, where processes are removed by simply killing them; no user code (including this callback) is executed when doing so.

它是在模拟环境下调用的，在真机中永远不会被调用。那为什么那么多app的Application类都用到这个方法呢？下面写一个demo测试一下，看结果如何。

首先在真机测试，代码：

import android.app.Application;
public class APP extends Application{
        @Override
        public void onCreate() {
               // TODO Auto-generated method stub
               super.onCreate();
              System. out.println("onCreate()" );
       }
        @Override
        public void onLowMemory() {
               // TODO Auto-generated method stub
               super.onLowMemory();
              System. out.println("onCreate()" );
       }
        @Override
        public void onTerminate() {
               // TODO Auto-generated method stub
               super.onTerminate();
              System. out.println("onCreate()" );
       }
       
}

结果：

打开程序的时候调用了ocCreate()方法，这个没有问题，下面退出程序看看。我直接按返回家退出，发现并没有调用onTerminate()方法。接下来使用模拟器看看结果如何：

运行程序，发现调用了ocCreate()方法，

退出程序看看，发现也没有调用。所以感觉onTerminate()这个方法还是不要使用为好，官方既然说了不会再真机中调用，那么应该不会有错。所以在很多app里面使用到了这个方法，有点不明觉厉，明白的朋友可以交流一下。