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>
![什么是空指针异常](https://p.xsw88.cn/allimgs/daicuo/20230907/6575.png)
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。
解决方案您需要调用的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: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:
< 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= />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:
@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。
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 any View
s such as the Toolbar
.
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.
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