我知道这个问题已经存在,但我想serveral的解决方案,并没有为我工作。
在我的情况,我需要一个开关
按钮的动作条。
项目
的id在定义的XML
编辑:异常点在code标有注释。它在mainactivity。 :)
下面是我的一些code:
mainactivity:
@覆盖
保护无效的onCreate(包savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_minepedia_main);
switchButton =(开关)findViewById(R.id.switch_button);
//下面这行抛出一个异常,因为switchButton
//为空,即使我试图把它的上线。
switchButton.setOnCheckedChangeListener(新CompoundButton.OnCheckedChangeListener(){
@覆盖
公共无效onCheckedChanged(CompoundButton buttonView,布尔器isChecked){
//下面是一个局部布尔变量
如果(器isChecked){
ONLINE_MODE_ENABLED = TRUE;
} 其他 {
ONLINE_MODE_ENABLED = FALSE;
}
}
});
}
@覆盖
公共布尔onCreateOptionsMenu(功能菜单){
//充气菜单; - > main_actions.xml
。getMenuInflater()膨胀(R.menu.main_actions,菜单);
返回super.onCreateOptionsMenu(菜单);
}
mainactivity_layout:
< RelativeLayout的的xmlns:机器人=http://schemas.android.com/apk/res/android
的xmlns:工具=http://schemas.android.com/tools
机器人:layout_width =match_parent
机器人:layout_height =match_parent
机器人:以下属性来=@扪/ activity_horizontal_margin
机器人:paddingRight =@扪/ activity_horizontal_margin
机器人:paddingTop =@扪/ activity_vertical_margin
机器人:paddingBottom会=@扪/ activity_vertical_margin
工具:上下文=Minepedia_main。>
<的LinearLayout
机器人:layout_width =200dp
机器人:layout_height =match_parent
机器人:方向=垂直
机器人:layout_centerInParent =真
机器人:重力=中心>
<按钮
机器人:layout_width =match_parent
机器人:layout_height =WRAP_CONTENT
机器人:文本=@字符串/ items_button
机器人:的onClick =startItemsMenu/>
<按钮
机器人:layout_width =match_parent
机器人:layout_height =WRAP_CONTENT
机器人:文本=@字符串/ about_button
机器人:的onClick =startAboutScreen/>
<的LinearLayout
机器人:layout_width =match_parent
机器人:layout_height =WRAP_CONTENT
机器人:重力=底
机器人:paddingTop =50dp
机器人:方向=垂直>
<按钮
机器人:layout_width =match_parent
机器人:layout_height =WRAP_CONTENT
机器人:文本=@字符串/ update_offline_button
机器人:的onClick =startOfflineUpdate/>
<的TextView
机器人:layout_width =WRAP_CONTENT
机器人:layout_height =WRAP_CONTENT
机器人:textAppearance =机器人:ATTR / textAppearanceSmall
机器人:文本=@字符串/ offline_sync_info
机器人:ID =@ + ID / TextView的
机器人:layout_gravity =center_horizontal/>
< / LinearLayout中>
< / LinearLayout中>
< / RelativeLayout的>
main_actions.xml(菜单):
<菜单的xmlns:机器人=http://schemas.android.com/apk/res/android
的xmlns:yourapp =http://schemas.android.com/apk/res-auto>
< - !搜索,应显示为操作按钮 - >
<项目
机器人:ID =@ + ID /是myswitch
机器人:标题=
机器人:showAsAction =总是
机器人:actionLayout =@布局/ switch_layout
/>
< /菜单>
switch_layout.xml:
< XML版本=1.0编码=UTF-8&GT?;
< RelativeLayout的的xmlns:机器人=http://schemas.android.com/apk/res/android
机器人:layout_width =match_parent
机器人:layout_height =match_parent>
<开关
机器人:ID =@ + ID / switch_button
机器人:layout_width =WRAP_CONTENT
机器人:layout_height =match_parent
机器人:文本=
机器人:textOff =离线
机器人:纹元=在线/>
< / RelativeLayout的>
堆栈跟踪:
08-20 17:45:52.902 5534-5534 / com.nubage.minepedia E / AndroidRuntime:致命异常:主要
工艺:com.nubage.minepedia,PID:5534
显示java.lang.NullPointerException
在com.nubage.minepedia.Minepedia_main.onCreateOptionsMenu(Minepedia_main.java:63)
在android.app.Activity.onCreatePanelMenu(Activity.java:2538)
在com.android.internal.policy.impl.PhoneWindow。preparePanel(PhoneWindow.java:489)
在com.android.internal.policy.impl.PhoneWindow.doInvalidatePanelMenu(PhoneWindow.java:853)
在com.android.internal.policy.impl.PhoneWindow $ 1.运行(PhoneWindow.java:273)
在android.view.Choreographer $ CallbackRecord.run(Choreographer.java:761)
在android.view.Choreographer.doCallbacks(Choreographer.java:574)
在android.view.Choreographer.doFrame(Choreographer.java:543)
在android.view.Choreographer $ FrameDisplayEventReceiver.run(Choreographer.java:747)
在android.os.Handler.handleCallback(Handler.java:733)
在android.os.Handler.dispatchMessage(Handler.java:95)
在android.os.Looper.loop(Looper.java:136)
在android.app.ActivityThread.main(ActivityThread.java:5081)
在java.lang.reflect.Method.invokeNative(本机方法)
在java.lang.reflect.Method.invoke(Method.java:515)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:791)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
在dalvik.system.NativeStart.main(本机方法)
解决方案
由ρяσѕρєяK'按照答案,但改变code他的下面一行:
菜单项项= menu.findItem(R.id.switch_button);
这样:
菜单项项= menu.findItem(R.id.myswitch); //该ID被改变!
这应该摆脱NullPointerException异常的,希望这有助于:)
所以,你应该是这样的:
@覆盖
保护无效的onCreate(包savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_minepedia_main);
}
@覆盖
公共布尔onCreateOptionsMenu(功能菜单){
MenuInflater充气= getMenuInflater();
inflater.inflate(R.menu.main_actions,菜单);
菜单项项= menu.findItem(R.id.myswitch);
switchButton =(开关)item.getActionView();
switchButton.setOnCheckedChangeListener(新CompoundButton.OnCheckedChangeListener({
@覆盖
公共无效onCheckedChanged(CompoundButton buttonView,布尔器isChecked){
//下面是一个局部布尔变量
如果(器isChecked){
ONLINE_MODE_ENABLED = TRUE;
} 其他 {
ONLINE_MODE_ENABLED = FALSE;
}
}
});
返回super.onCreateOptionsMenu(菜单);
}
此外改变这一行:
安卓actionLayout =@布局/ switch_layout
这样:
安卓actionViewClass =android.widget.Switch
这是你的菜单XML中。如果您应用的变化,那么你使用的是由机器人提供的开关按钮和必须的工作。
I know this question already exists, but I tried serveral solutions and none worked for me.
In my case, I need a Switch
Button in the ActionBar.
item
in the defined xml
Edit: The exception-point in the code is marked with a comments. It's in the mainactivity. :)
Here is some of my code:
mainactivity:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_minepedia_main);
switchButton = (Switch) findViewById(R.id.switch_button);
//The following line throws an exception, because switchButton
//is null, even though I tried to take it on the upper line.
switchButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
//The following is a local boolean variable
if (isChecked) {
ONLINE_MODE_ENABLED = true;
} else {
ONLINE_MODE_ENABLED = false;
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; --> main_actions.xml
getMenuInflater().inflate(R.menu.main_actions, menu);
return super.onCreateOptionsMenu(menu);
}
mainactivity_layout:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".Minepedia_main">
<LinearLayout
android:layout_width="200dp"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_centerInParent="true"
android:gravity="center" >
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/items_button"
android:onClick="startItemsMenu" />
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/about_button"
android:onClick="startAboutScreen" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="bottom"
android:paddingTop="50dp"
android:orientation="vertical">
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/update_offline_button"
android:onClick="startOfflineUpdate"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="@string/offline_sync_info"
android:id="@+id/textView"
android:layout_gravity="center_horizontal" />
</LinearLayout>
</LinearLayout>
</RelativeLayout>
main_actions.xml (menu):
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:yourapp="http://schemas.android.com/apk/res-auto" >
<!-- Search, should appear as action button -->
<item
android:id="@+id/myswitch"
android:title=""
android:showAsAction="always"
android:actionLayout="@layout/switch_layout"
/>
</menu>
switch_layout.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Switch
android:id="@+id/switch_button"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text=""
android:textOff="Offline"
android:textOn="Online"/>
</RelativeLayout>
Stacktrace:
08-20 17:45:52.902 5534-5534/com.nubage.minepedia E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.nubage.minepedia, PID: 5534
java.lang.NullPointerException
at com.nubage.minepedia.Minepedia_main.onCreateOptionsMenu(Minepedia_main.java:63)
at android.app.Activity.onCreatePanelMenu(Activity.java:2538)
at com.android.internal.policy.impl.PhoneWindow.preparePanel(PhoneWindow.java:489)
at com.android.internal.policy.impl.PhoneWindow.doInvalidatePanelMenu(PhoneWindow.java:853)
at com.android.internal.policy.impl.PhoneWindow$1.run(PhoneWindow.java:273)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:543)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5081)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
at dalvik.system.NativeStart.main(Native Method)
解决方案
Follow the answer by 'ρяσѕρєя K' but change his following line of code:
MenuItem item = menu.findItem(R.id.switch_button);
to this:
MenuItem item = menu.findItem(R.id.myswitch); //the id was changed!
That should get rid of the NullPointerException, hope this helps :)
So you should have something like this:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_minepedia_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main_actions, menu);
MenuItem item = menu.findItem(R.id.myswitch);
switchButton = (Switch)item.getActionView();
switchButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener({
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
//The following is a local boolean variable
if (isChecked) {
ONLINE_MODE_ENABLED = true;
} else {
ONLINE_MODE_ENABLED = false;
}
}
});
return super.onCreateOptionsMenu(menu);
}
Additionally change this line:
android:actionLayout="@layout/switch_layout"
to this:
android:actionViewClass="android.widget.Switch"
That is within your menu xml. If you apply that change then you are using the switch button provided by android and that must work.
上一篇:难道ProGuard的工作混淆静态字符串常量?常量、字符串、静态、工作
下一篇:startActivity()从BroadcastReceiver的startActivity、BroadcastReceiver