Could not find class when application is loaded into emulator

I have an activity (DemoAppActivity) from which I am trying to launch a different activity (MainActivity) when a button is pressed. However I am getting two 开发者_运维问答errors:

1) when the app is loaded into the emulator, I see the following in the Android logs:

10-12 18:48:19.579: ERROR/dalvikvm(620): Could not find class 'com.example.android.hcgallery.MainActivity', referenced from method com.consultknapp.demoapp.DemoAppActivity$1.onClick

2) when i actually push the button that calls startActivity:

10-12 18:54:58.019: ERROR/AndroidRuntime(620): java.lang.NoClassDefFoundError: com.example.android.hcgallery.MainActivity

Here is how I am starting the activity (note: I import the class with an import statment, import com.example.android.hcgallery.MainActivity)

startActivity(new Intent(DemoAppActivity.this, MainActivity.class));

I have the MainActivity project folder in my build path in eclipse, and I even see it load the MainActivity.apk when I compile/run my DemoAppActivity. However, it bombs when I try to run it on the emulator.

What am I missing here? Do I need to jar up my MainActivity and include it in the DemoAppActivity somehow?

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I was able to figure it out from another post. Basically you need to do this with the Intent before starting the activity:

Intent i = new Intent();
i.setComponent(new ComponentName("com.example.android.hcgallery", "com.example.android.hcgallery.MainActivity"));
startActivity(i);

The setComponent tells the class loader to make it available. After adding that code, it worked!