安卓导航抽屉“汉堡包”不可见

Question

我正在从Android应用程序中添加新的导航抽屉活动的Android应用程序。即使抽屉出现，汉堡包图标也不会出现。我如何去做这件事？ 请参见下面的默认代码：

public class NavigationDrawer extends AppCompatActivity 
    implements NavigationView.OnNavigationItemSelectedListener { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_navigation_drawer); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
    fab.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      Snackbar.make(view, "Connect to database", Snackbar.LENGTH_LONG) 
        .setAction("Action", null).show(); 
     } 
    }); 

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 

    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
      this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
    drawer.setDrawerListener(toggle); 
    toggle.syncState(); 

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
    navigationView.setNavigationItemSelectedListener(this); 
} 

@Override 
public void onBackPressed() { 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    if (drawer.isDrawerOpen(GravityCompat.START)) { 
     drawer.closeDrawer(GravityCompat.START); 
    } else { 
     super.onBackPressed(); 
    } 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.navigation_drawer, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 

    //noinspection SimplifiableIfStatement 
    if (id == R.id.action_settings) { 
     return true; 
    } 

    return super.onOptionsItemSelected(item); 
} 

@SuppressWarnings("StatementWithEmptyBody") 
@Override 
public boolean onNavigationItemSelected(MenuItem item) { 
    // Handle navigation view item clicks here. 
    int id = item.getItemId(); 

    if (id == R.id.nav_camera) { 
     // Handle the camera action 
    } else if (id == R.id.nav_gallery) { 

    } else if (id == R.id.nav_slideshow) { 

    } else if (id == R.id.nav_manage) { 

    } else if (id == R.id.nav_share) { 

    } else if (id == R.id.nav_send) { 

    } 

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    drawer.closeDrawer(GravityCompat.START); 
    return true; 
} 

}

Answer 1

删除

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
setSupportActionBar(toolbar); 

Answer 2

我不知道这将解决你的问题，但ActionBarDrawerToggle documentation说：

要使用ActionBarDrawerToggle，请在您的Activity中创建一个，并调用以下与t相对应的方法Ø你的Activity回调：

onConfigurationChanged

onOptionsItemSelected从活动的onPostCreate

呼叫syncState（）发生onRestoreInstanceState后的指标与链接DrawerLayout的状态同步。

所以你应该把ActionBarDrawerToggle toggle为一个类的成员，然后调用：

• toggle.syncState()到onPostCreate()方法
• toggle.onConfigurationChanged()到方法
• toggle.onOptionsItemSelected()到onOptionsItemSelected()方法

也可以从onCreate()方法中删除toggle.syncState()呼叫。

public class NavigationDrawer extends AppCompatActivity 
     implements NavigationView.OnNavigationItemSelectedListener { 

    private ActionBarDrawerToggle mToggle; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_navigation_drawer); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Connect to database", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 

     mToggle = new ActionBarDrawerToggle(
       this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
     drawer.setDrawerListener(mToggle); 

     NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
     navigationView.setNavigationItemSelectedListener(this); 
    } 

    @Override 
    protected void onPostCreate(Bundle savedInstanceState){ 
     super.onPostCreate(savedInstanceState); 
     mToggle.syncState(); 
    } 

    @Override 
    public void onConfigurationChanged(Configuration newConfig) { 
     super.onConfigurationChanged(newConfig); 
     mToggle.onConfigurationChanged(newConfig); 
    } 

    @Override 
    public void onBackPressed() { 
     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     if (drawer.isDrawerOpen(GravityCompat.START)) { 
      drawer.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.navigation_drawer, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     mToggle.onOptionsItemSelected(item); 

     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

    @SuppressWarnings("StatementWithEmptyBody") 
    @Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     // Handle navigation view item clicks here. 
     int id = item.getItemId(); 

     if (id == R.id.nav_camera) { 
      // Handle the camera action 
     } else if (id == R.id.nav_gallery) { 

     } else if (id == R.id.nav_slideshow) { 

     } else if (id == R.id.nav_manage) { 

     } else if (id == R.id.nav_share) { 

     } else if (id == R.id.nav_send) { 

     } 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 
} 

Answer 3

添加此之后

getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
getSupportActionBar().setHomeButtonEnabled(true); 

setSupportActionBar