我与jtwitter.jar库同样的问题。如果你运行的是Android工作室，你必须做一个干净的＆放大器;建设（其中AS不真正做对了）。

I had the same issue with the jtwitter.jar library. If you're running Android Studio, you have to do a clean & build (which AS doesn't truly do right now).

转到您的命令行，导航到你的项目的根和执行 ./ gradlew干净

Go to your command line, navigate to your project root and execute ./gradlew clean

你这样做之前

请确保您的.jar文件添加到您的 /库文件夹（如果您使用的是建立17或更高版本，它必须是库，而不是 LIB ）。右键单击并选择的添加为图书馆... 的

Ensure that your .jar file is added to your /libs folder (if you're using build 17 or later, it has to be libs, and not lib). Right-click and select Add as Library...

然后你将不得不编辑您的build.gradle文件（位于 / src目录目录）。

Then you're going to have to edit your build.gradle file (located in your /src directory).

这应该是这个样子：

buildscript {
    repositories {
        maven { url 'http://repo1.maven.org/maven2' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.4'
    }
}
apply plugin: 'android'

dependencies {
    compile files('libs/android-support-v4.jar')
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 5
        targetSdkVersion 16
    }
}

更改依赖块看起来是这样的：

Change the dependencies block to look like this:

dependencies {
    compile files('libs/android-support-v4.jar')
    compile files('[path/to/.jar]')
}

然后就可以生成并运行您的项目。

Then you can build and run your project.