Launch an external activity with its package and class name. For example, the package name is "com.example.hello", and the class name is "com.example.hello.MainActivity".

AndroidLaunchExternalActivity.java

/**
 * Launch an activity.
 * @param context The context to use. Usually your Application or Activity object.
 * @param packageName The name of the package that the component exists in. Can not be null.
 * @param className The name of the class inside of pkg that implements the component. Can not be null.
 * @see {ANDROID_SDK}/samples/android-{VERSION}/Home/src/com/example/android/home/Home.java
 */
private void launch(Context context, String packageName, String className) {
	if (context == null || packageName == null || className == null)
		return;
	ComponentName component = new ComponentName(packageName, className);
	Intent intent = new Intent(Intent.ACTION_MAIN);
	intent.addCategory(Intent.CATEGORY_LAUNCHER);
	intent.setComponent(component);
	intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
	try {
		context.startActivity(intent);
	} catch (Exception e) {
		Log.v(TAG, e.toString());
	}
}

intent.addCategory(Intent.CATEGORY_LAUNCHER) and intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) are very important.