My MainActivity class throws java.lang.ClassNotFoundException when extends ActionBarActivity

问题

I followed the instructions indicated in other threads on how to import external libraries, but after importing android-support-v7-appcompat.jar into the Referenced Libraries of my Android project (in ADT v.22.0.5) I get java.lang.ClassNotFoundException:

import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        }
}

Can someone please shed some light?

回答1:

Go the "Java Build Path" -> Order and export -> check all checkboxes -> clean -> build -> run

回答2:

You must add the class path to your new library.

You can see a file named .classpath, specify the path to your new library.

<classpathentry kind="lib" path="<path to your .jar file>"/>

回答3:

I fixed it following these instructions:

1. How to set up ActionBarCompat in Eclipse

2. How to implement Action Bar using ActionBarCompat

来源：https://stackoverflow.com/questions/18565956/my-mainactivity-class-throws-java-lang-classnotfoundexception-when-extends-actio