1.我们又需要考虑如果这个手机没有SD卡，或者SD正好被移除了的情况因此需要这个工具类判断

public File getDiskCacheDir(Context context, String uniqueName) {  
    String cachePath;  
    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())  
            || !Environment.isExternalStorageRemovable()) {  
        cachePath = context.getExternalCacheDir().getPath();  
    } else {  
        cachePath = context.getCacheDir().getPath();  
    }  
    return new File(cachePath + File.separator + uniqueName);  
}  

2.获取到当前应用程序的版本号

public int getAppVersion(Context context) {  
    try {  
        PackageInfo info = context.getPackageManager().getPackageInfo(context.getPackageName(), 0);  
        return info.versionCode;  
    } catch (NameNotFoundException e) {  
        e.printStackTrace();  
    }  
    return 1;  
}