改变汉堡包图标

Question

我想更改汉堡包图标。我能够第一次更改图标然后我不喜欢这个并想用另一个图标更改它。现在问题是它没有改变和它只显示第一个图标。任何人都告诉我该怎么做

这是我的主要活动代码

package com.example.alpit.formula2;

 import android.support.v4.app.ActionBarDrawerToggle;
 import android.support.v4.widget.DrawerLayout;
 import android.support.design.widget.NavigationView;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.support.v7.widget.GridLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.view.MenuItem;
 import android.support.v7.widget.Toolbar;
 public class MainActivity extends AppCompatActivity {

private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle aToggle;
private Toolbar toolbar;
private RecyclerView recyclerView;
private RecyclerAdapter recyclerAdapter;
private RecyclerView.Adapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mDrawerLayout=(DrawerLayout)findViewById(R.id.drawer);
    aToggle=new    ActionBarDrawerToggle(this,mDrawerLayout,R.drawable.menuicon,R.string.open,R.string.Close);
    NavigationView navigationView=(NavigationView)findViewById(R.id.nav_view);
    mDrawerLayout.addDrawerListener(aToggle);
    toolbar=(Toolbar)findViewById(R.id.nav_action);
    setSupportActionBar(toolbar);
    aToggle.syncState();
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    navigationView.setItemIconTintList(null);
    recyclerView=(RecyclerView)findViewById(R.id.recycler);
    recyclerAdapter=new RecyclerAdapter(getApplicationContext());
    RecyclerView.LayoutManager layoutManager= new GridLayoutManager(this,2);
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(recyclerAdapter);
     }
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if(aToggle.onOptionsItemSelected(item)){
        return true;
    }
    return super.onOptionsItemSelected(item);
}}