对context的解释：

Interface to global information about an application environment. This is　an abstract class whose implementation is provided by the Android system. It　allows access to application-specific resources and classes, as well as up-calls for application-level operations such as launching activities, broadcasting and receiving intents, etc.

我们熟知几个类Application 、Activity 、Service与Context的关系

ContextWrapper extends Context

Application extends ContextWrapper

Service extends ContextWrapper

ContextThemeWrapper extemds ContextWrapper

Activity extends ContextThemeWrapper

Application几个关键方法：

attach(Context)->attachBaseContext(Context)调用到ContextWrapper中

ContextImpl之分析几个方法

databaseList()

@Override
    public String[] databaseList() {
        return FileUtils.listOrEmpty(getDatabasesDir());
    }

    private File getDatabasesDir() {
        synchronized (mSync) {
            if (mDatabasesDir == null) {
                if ("android".equals(getPackageName())) {
                    mDatabasesDir = new File("/data/system");
                } else {
                    mDatabasesDir = new File(getDataDir(), "databases");
                }
            }
            return ensurePrivateDirExists(mDatabasesDir);
        }
    }

//方法的测试数据

String[] fileDAList = mContext.databaseList();//

获取的是/data/data/包名/databases/文件夹下的 db文件

String[] fileList = mContext.fileList();//

获取的是/data/data包名/files/文件夹下的 文件

ApplicationInfo applicationInfo = mContext.getApplicationInfo();//

String dataDir = applicationInfo.dataDir;//

  /data/user/0/com.example.wangwujun.myapplication

String deviceProtectedDataDir = applicationInfo.deviceProtectedDataDir;//

  /data/user\_de/0/com.example.wangwujun.myapplication

String nativeLibraryDir = applicationInfo.nativeLibraryDir;//

 /data/app/com.example.wangwujun.myapplication-1/lib/arm

String publicSourceDir = applicationInfo.publicSourceDir;//

 /data/app/com.example.wangwujun.myapplication-1/base.apk

String sourceDir = applicationInfo.sourceDir;//

 /data/app/com.example.wangwujun.myapplication-1/base.apk

String[] strings = applicationInfo.sharedLibraryFiles;// 未获得值

String[] splitPublicSourceDirs = applicationInfo.splitPublicSourceDirs;

 /data/app/com.example.wangwujun.myapplication-1/split\_lib\_dependencies\_apk.apk

 /data/app/com.example.wangwujun.myapplication-1/split\_lib\_slice\_xx\_apk.apk

String[] splitSourceDirs = applicationInfo.splitSourceDirs;//

/data/app/com.example.wangwujun.myapplication-1/split\_lib\_dependencies\_apk.apk

/data/app/com.example.wangwujun.myapplication-1/split_lib_slice_xx_apk.apk