创建一个新的安卓应用程序 设置主Activity

public class MainActivity extends Activity{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mainactivity);
    }
}

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