java.lang.NoClassDefFoundError: com.squareup.okhttp.OkHttpClient如何解决

OSS存储，上传图片时报错

??-?? ??:??:??.???: INFO/(): java.lang.NoClassDefFoundError:com.squareup.okhttp.OkHttpClient
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at com.alibaba.sdk.android.oss.internal.InternalRequestOperation.(InternalRequestOperation.java:77)
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at com.alibaba.sdk.android.oss.OSSClient.(OSSClient.java:100)
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at xy.aliyunoss.AliyunOssActivity.onCreate(AliyunOssActivity.java:80)
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at android.app.Activity.performCreate(Activity.java:5320)
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at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
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at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2161)
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at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
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at android.app.ActivityThread.access$800(ActivityThread.java:143)
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at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1209)
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at android.os.Handler.dispatchMessage(Handler.java:102)
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at android.os.Looper.loop(Looper.java:136)
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at android.app.ActivityThread.main(ActivityThread.java:5120)
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at java.lang.reflect.Method.invokeNative(Native Method)
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at java.lang.reflect.Method.invoke(Method.java:515)
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at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:818)
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at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:634)
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at dalvik.system.NativeStart.main(Native Method)