与得到的工具栏

下的导航图标的问题是Java代码：与得到的工具栏

public class Displayprofile extends AppCompatActivity { 

    private DrawerLayout mDrawerLayout; 
    private ActionBarDrawerToggle mToggle; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.displayprofile); 
     mDrawerLayout = (DrawerLayout)findViewById(R.id.drawerlayout) ; 
     mToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close); 
     getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
     mDrawerLayout.addDrawerListener(mToggle); 
     mToggle.syncState(); 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     if (mToggle.onOptionsItemSelected(item)) 
     { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

}

导航图标不显示。否则，导航菜单工作得很好。每当添加getSupportActionBar().setDisplayHomeAsUpEnabled(true);时，该应用程序崩溃。无论何时该语句被遗漏，该应用程序不会崩溃。本次活动的主题是如下：

<style name="mainthemered" parent="Theme.AppCompat.Light.DarkActionBar"> 
    <item name="colorAccent">@color/colorLogoRed</item> 
</style>

的错误是如下：

12-06 21:23:11.256 22417-22417/com.example.krsnv.kooc E/AndroidRuntime: FATAL EXCEPTION: main 
    Process: com.example.krsnv.kooc, PID: 22417 
     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.krsnv.kooc/com.example.krsnv.kooc.Displayprofile}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:148) 
      at android.app.ActivityThread.main(ActivityThread.java:5422) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference 
      at com.example.krsnv.kooc.Displayprofile.onCreate(Displayprofile.java:47) 
      at android.app.Activity.performCreate(Activity.java:6251) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)  
      at android.app.ActivityThread.-wrap11(ActivityThread.java)  
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)  
      at android.os.Handler.dispatchMessage(Handler.java:102)  
      at android.os.Looper.loop(Looper.java:148)  
      at android.app.ActivityThread.main(ActivityThread.java:5422)  
      at java.lang.reflect.Method.invoke(Native Method)  
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)  
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

来源

2016-12-06 Chirag

你看到的错误是什么？ getSupportActionBar（）是否为空？ – Nico

可以发布更多的版本，或者发布错误 –

将'mainthemered'风格的父类更改为'Theme.AppCompat.Light.NoActionBar'。 –

设置你的支援行动吧？

Toolbar myToolbar = (Toolbar) findViewById(R.id.your_toolbar); 
setSupportActionBar(myToolbar); 
getSupportActionBar().setTitle("Your title"); 
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

来源

2016-12-06 15:59:43 JamesSwinton

与得到的工具栏

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