setSupportActionBar()抛出空指针异常 [英] setSupportActionBar() throws Nullpointer exception
问题描述
我是新来的Android和我是以下材料设计工具栏下面的教程:
http://www.android4devs.com/2014/12/how-to-make-material-design-app.html
不过,code的实施后。在logcat中表现出以下错误:
04-01 19:16:10.214 2246年至2253年/ com.example.bhaskar.ddit_results E /艺术:发送失败回复调试器:断的管
04-01 19:16:11.985 2246年至2246年/ com.example.bhaskar.ddit_results E / AndroidRuntime:致命异常:主要
工艺:com.example.bhaskar.ddit_results,PID:2246
了java.lang.RuntimeException:无法启动活动ComponentInfo {com.example.bhaskar.ddit_results / com.example.bhaskar.ddit_results.MainActivity}:显示java.lang.NullPointerException:尝试调用虚拟方法java.lang.CharSequence中的机器人。 support.v7.widget.Toolbar.getTitle()在空对象引用
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
在android.app.ActivityThread.access $ 800(ActivityThread.java:144)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1278)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5221)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
显示java.lang.NullPointerException:引起试图调用虚拟方法java.lang.CharSequence中android.support.v7.widget.Toolbar.getTitle()在空对象引用
在android.support.v7.internal.widget.ToolbarWidgetWrapper<&初始化GT;(ToolbarWidgetWrapper.java:95)
在android.support.v7.internal.widget.ToolbarWidgetWrapper<&初始化GT;(ToolbarWidgetWrapper.java:88)
在android.support.v7.internal.app.ToolbarActionBar<&初始化GT;(ToolbarActionBar.java:84)
在android.support.v7.app.ActionBarActivityDelegateBase.setSupportActionBar(ActionBarActivityDelegateBase.java:175)
在android.support.v7.app.ActionBarActivity.setSupportActionBar(ActionBarActivity.java:92)
在com.example.bhaskar.ddit_results.MainActivity.onCreate(MainActivity.java:41)
在android.app.Activity.performCreate(Activity.java:5933)
在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
在android.app.ActivityThread.access $ 800(ActivityThread.java:144)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1278)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5221)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
采用了Android 1.0.1工作室我这是由NullPointerException.I造成的。
styles.xml:
<资源><! - Base应用程序的主题。 - >
<样式名称=MyTheme的父=MyTheme.Base>< /风格><样式名称=MyTheme.Base父=Theme.AppCompat.Light.NoActionBar> <项目名称=colorPrimary>#FF32CD32< /项目>
<项目名称=colorPrimaryDark>#ff04cd2c< /项目>
<项目名称=colorAccent>#ff4081< /项目>
< /风格>
V21 / styles.xml:
<资源>
<样式名称=MyTheme的父=MyTheme.Base>
<项目名称=机器人:windowContentTransitions>真< /项目>
<项目名称=机器人:windowAllowEnterTransitionOverlap>真< /项目>
<项目名称=机器人:windowAllowReturnTransitionOverlap>真< /项目>
<项目名称=机器人:windowSharedElementEnterTransition> @android:过渡/移动< /项目>
<项目名称=机器人:windowSharedElementExitTransition> @android:过渡/移动< /项目>
在toolbar.xml我:
< android.support.v7.widget.Toolbar的xmlns:机器人=http://schemas.android.com/apk/res/android
的xmlns:程序=http://schemas.android.com/apk/res-auto
机器人:ID =@ + ID /工具栏
机器人:layout_width =match_parent
机器人:layout_height =WRAP_CONTENT
机器人:ATTR / colorPrimary背景=
应用:主题=@风格/ ThemeOverlay.AppCompat.Dark.ActionBar
应用:popupTheme =@风格/ ThemeOverlay.AppCompat.Light
机器人:海拔=4DP/>
此外,我已经包括在activity_main.xml中文件的工具栏布局。
在MainActivity.java:
公共类MainActivity扩展ActionBarActivity {....私人工具栏工具栏;
公共静态最终诠释RECORD_ENTRY_REQUEST_ code = 3;@覆盖
保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
//从主布局资源设置我们的观点 工具栏=(栏)findViewById(R.id.toolbar); //工具栏现在就默认动作条特色
的setContentView(R.layout.activity_main);
setSupportActionBar(工具栏);
的setTitle(DDIT_Results);
....}
我搜索了这个问题,并没有拿出任何solutions.Hopefully,有人认识到这个错误,都是有快速的答案 - 否则我可以提供,如果requested.Any帮助将appriciated更多信息。
您需要调用的setContentView
之前添加任何查看
S使得作为工具栏
。
保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_main); //< - 首先调用此 工具栏=(栏)findViewById(R.id.toolbar); //< - 设置意见后, setSupportActionBar(工具栏);
的setTitle(DDIT_Results);
}
请参阅官方Android开发者博客在这里:<一href=\"http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-$p$p.html\">http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-$p$p.html
操作栏
要使用工具栏作为一个操作栏,首先禁用所提供的装饰,
操作栏。最简单的方法是让你的主题,从延长
Theme.AppCompat.NoActionBar(或其变种光)。
二,创建工具栏的实例,通常是通过你的布局XML:
块引用>&LT; android.support.v7.widget.Toolbar
机器人:ID =@ + ID / my_awesome_toolbar
机器人:layout_height =WRAP_CONTENT
机器人:layout_width =match_parent
安卓了minHeight =?ATTR / actionBarSize
机器人:后台= /&gt;中ATTR / colorPrimary?
的高度,宽度,背景等方面都完全取决于你;这些
只是很好的例子。由于工具栏只是一个ViewGroup中,你可以风格
并把它不过你想要的。
然后在你的活动或片段,设置工具栏作为您
操作栏:
块引用>@覆盖
公共无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.blah); 工具条工具栏=(栏)findViewById(R.id.my_awesome_toolbar);
setSupportActionBar(工具栏);
}
从这时起,所有菜单项都显示在您的工具栏,
通过标准的选项菜单回调填充。
块引用>I am new to android and i was following following tutorial for Material Design Toolbar :
http://www.android4devs.com/2014/12/how-to-make-material-design-app.html
But after Implementation of the code. following error was shown in logcat :
04-01 19:16:10.214 2246-2253/com.example.bhaskar.ddit_results E/art﹕ Failed sending reply to debugger: Broken pipe 04-01 19:16:11.985 2246-2246/com.example.bhaskar.ddit_results E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.bhaskar.ddit_results, PID: 2246 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bhaskar.ddit_results/com.example.bhaskar.ddit_results.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:95) at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:88) at android.support.v7.internal.app.ToolbarActionBar.<init>(ToolbarActionBar.java:84) at android.support.v7.app.ActionBarActivityDelegateBase.setSupportActionBar(ActionBarActivityDelegateBase.java:175) at android.support.v7.app.ActionBarActivity.setSupportActionBar(ActionBarActivity.java:92) at com.example.bhaskar.ddit_results.MainActivity.onCreate(MainActivity.java:41) at android.app.Activity.performCreate(Activity.java:5933) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
which is caused by NullPointerException.I am using Android Studio 1.0.1.
styles.xml :
<resources> <!-- Base application theme. --> <style name="MyTheme" parent="MyTheme.Base"> </style> <style name="MyTheme.Base" parent="Theme.AppCompat.Light.NoActionBar"> <item name="colorPrimary">#ff32cd32</item> <item name="colorPrimaryDark">#ff04cd2c</item> <item name="colorAccent">#ff4081</item> </style>
v21/styles.xml:
<resources> <style name="MyTheme" parent="MyTheme.Base"> <item name="android:windowContentTransitions">true</item> <item name="android:windowAllowEnterTransitionOverlap">true</item> <item name="android:windowAllowReturnTransitionOverlap">true</item> <item name="android:windowSharedElementEnterTransition">@android:transition/move</item> <item name="android:windowSharedElementExitTransition">@android:transition/move</item>
In toolbar.xml i've :
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/colorPrimary" app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" app:popupTheme="@style/ThemeOverlay.AppCompat.Light" android:elevation="4dp"/>
also i've included the toolbar layout in activity_main.xml file. In MainActivity.java :
public class MainActivity extends ActionBarActivity { .... private Toolbar toolbar; public static final int RECORD_ENTRY_REQUEST_CODE=3; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set our view from the "main" layout resource toolbar = (Toolbar)findViewById(R.id.toolbar); //Toolbar will now take on default actionbar characteristics setContentView(R.layout.activity_main); setSupportActionBar(toolbar); setTitle("DDIT_Results"); .... }
I searched for this problem and didn't come up with any solutions.Hopefully, someone recognizes this error and has a quick answer for it - otherwise I can provide more information if requested.Any help would be appriciated.
解决方案You need to call
setContentView
BEFORE adding anyView
s such as theToolbar
.protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // <-- call this first toolbar = (Toolbar)findViewById(R.id.toolbar); // <-- setup views after setSupportActionBar(toolbar); setTitle("DDIT_Results"); }
Please see the Official Android Developers blog here: http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-pre.html
Action Bar
To use Toolbar as an Action Bar, first disable the decor-provided Action Bar. The easiest way is to have your theme extend from Theme.AppCompat.NoActionBar (or its light variant).
Second, create a Toolbar instance, usually via your layout XML:
<android.support.v7.widget.Toolbar android:id="@+id/my_awesome_toolbar" android:layout_height="wrap_content" android:layout_width="match_parent" android:minHeight="?attr/actionBarSize" android:background="?attr/colorPrimary" />
The height, width, background, and so on are totally up to you; these are just good examples. As Toolbar is just a ViewGroup, you can style and position it however you want.
Then in your Activity or Fragment, set the Toolbar to act as your Action Bar:
@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.blah); Toolbar toolbar = (Toolbar) findViewById(R.id.my_awesome_toolbar); setSupportActionBar(toolbar); }
From this point on, all menu items are displayed in your Toolbar, populated via the standard options menu callbacks.
这篇关于setSupportActionBar()抛出空指针异常的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!