Android studio 调试提示MainActivity未在Manifest中声明

Manifest.xml:
<?xml version="1.0" encoding="utf-8"?>
package="com.example.cheng.firstapp"
andriod:versionCode="1"
andriod:versionName="1.0">

<uses-sdk
    andriod:minSdkVersion="8"
    andriod:targetSdkVersion="21" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:screenOrientation="landscape"
        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>

MainActivity:
package com.example.cheng.firstapp;

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;

    public class MainActivity extends AppCompatActivity {//AppCompatActivity

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Log.d("Lifecycle","onCreate");
            setContentView(R.layout.activity_main);
}

public boolean onCreateOptionMenu(Menu menu){
    getMenuInflater().inflate(R.menu.menu_main,menu);
    return true;
}

public void onStart(){
    super.onStart();
    Log.d("lifestyle","onStart");
}

public void onRestart(){
    super.onStart();
    Log.d("Lifestyle","onStart");
}

public void onResume(){
    super.onResume();
}

public void onPause(){
    super.onPause();
    Log.d("Lifestyle","onPause");
}

public void onStop(){
    super.onStop();
    Log.d("Lifecycle","onStop");
}

public void onDestroy(){
    super.onDestroy();
    Log.d("Lifestyle","onDestroy");
}

}

https://www.baidu.com/link?url=WS7L9DQqZHHEf0IUzOwkXuY7CUUp9XubNF7-JXpuHYooYEGOsHPZRAk-Qm6WGfwJrRazfctVtrcv69IM1XN59HkIV6LBz_69wW0Y6d0t_6u&wd=&eqid=8d21d7da000d2d310000000458b8b4ad

我看不是注册清单的问题，是你的menu的方法实现不对，还有一个get子控件的方法没实现