ClassNotFoundException：在Android中的libs中添加了第三方JAR文件时发生

我正在使用jackrabbit jar文件（jackrabbit-webdav-2.2.5-jar-with-dependencies）在android mobile上开发webDav客户端-该JAR是针对android设备的自定义版本。

我已经在libs文件夹中添加了这个jar文件，它没有给我编译错误，但是当我在模拟器上运行.apk时，我得到了以下错误：

04-16 02:55:50.387: E/AndroidRuntime(2122): FATAL EXCEPTION: main
04-16 02:55:50.387: E/AndroidRuntime(2122): Process: com.example.jackrabbit, PID: 2122
04-16 02:55:50.387: E/AndroidRuntime(2122): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jackrabbit/com.example.jackrabbit.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.jackrabbit.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.jackrabbit-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.jackrabbit-1, /system/lib]]
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.os.Handler.dispatchMessage(Handler.java:102)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.os.Looper.loop(Looper.java:136)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread.main(ActivityThread.java:5017)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at java.lang.reflect.Method.invokeNative(Native Method)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at java.lang.reflect.Method.invoke(Method.java:515)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at dalvik.system.NativeStart.main(Native Method)
04-16 02:55:50.387: E/AndroidRuntime(2122): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.jackrabbit.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.jackrabbit-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.jackrabbit-1, /system/lib]]
04-16 02:55:50.387: E/AndroidRuntime(2122):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
04-16 02:55:50.387: E/AndroidRuntime(2122):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
04-16 02:55:50.387: E/AndroidRuntime(2122):     ... 11 more

下面是我的代码快照，用于连接到webDav服务器

package com.example.jackrabbit;

import org.apache.commons.httpclient.Credentials;
import org.apache.commons.httpclient.HostConfiguration;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthScope;
import org.apache.commons.httpclient.params.HttpConnectionManagerParams;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class webDavClient extends Activity {

    MultiThreadedHttpConnectionManager manager;
    HostConfiguration config;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btn = (Button)findViewById(R.id.button1);

        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                //webDav host configuration
                ConfigureHost();
                 //webDav client configuration
                 ConfigureClient();             
            }
        });
    }

    public void ConfigureHost() {
        //create host configuration
        HostConfiguration config = new HostConfiguration();
        config.setHost("http://webdav.in.soti.net");

        //setup connection manager
        manager = new MultiThreadedHttpConnectionManager();
        HttpConnectionManagerParams params = new HttpConnectionManagerParams();
        params.setMaxConnectionsPerHost(config, 5); // currently allowing 5 we may revise count afterwards

    }

    public void ConfigureClient() {
        //create client configuration
        HttpClient client = new HttpClient(manager);
        client.setHostConfiguration(config);
        Credentials creds = new UsernamePasswordCredentials("username", "password");
        client.getState().setCredentials(AuthScope.ANY, creds);
    }

}

以下是活动布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <Button
        android:id="@+id/button1"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="100dp"
        android:layout_marginTop="127dp"
        android:text="ConnectToServer" />

</RelativeLayout>

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.jackrabbit"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.jackrabbit.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

自早晨以来，请对此提供帮助，我对此感到困惑。

最好的问候，拉姆·罗特