NullPointerException with android.support.v7.widget.Toolbar
我目前正在尝试在我的应用中实现导航抽屉。我遇到了工具栏为空的问题。我在网上做了很多搜索，并尝试了许多不同的解决方案，但无济于事。我还没有写完所有代码，但我无法启动我的应用程序来检查导航抽屉。谁能看到我哪里做错了？
如果我还有其他需要发布的内容，请告诉我。
我在所有活动屏幕上都包含了这个
<include
android:id="@+id/app_bar"
layout="@layout/app_bar"/>
app_bar.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/ThemeOverlay.AppCompat.Dark" >
</android.support.v7.widget.Toolbar>
主要活动的第 72 行
setSupportActionBar(mToolbar);
主要活动
public class Trans_List extends ActionBarActivity {
private Toolbar mToolbar;
private CharSequence mTitle;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_trans_list);
mToolbar = (Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
NavigationDrawerFragment drawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.left_drawer);
drawerFragment.setUp((DrawerLayout) findViewById(R.id.drawer_layout), mToolbar);
风格.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="AppBaseTheme" parent="@style/Theme.AppCompat.Light.DarkActionBar" >
<item name="windowActionBar">false</item>
</style>
<style name="Theme.split" parent="AppBaseTheme">
</style>
<style name="dialog_custom" parent="@style/Theme.AppCompat.Dialog">
<item name="@android:listPreferredItemPaddingLeft">20dip</item>
<item name="@android:listPreferredItemPaddingRight">20dip</item>
<item name="@android:listPreferredItemPaddingStart">20dip</item>
<item name="@android:listPreferredItemPaddingEnd">20dip</item>
</style>
</resources>
日志猫
01-07 01:14:29.702 4811-4811/com.lee.yuchan.splt E/AndroidRuntime﹕
FATAL EXCEPTION: main
Process: com.lee.yuchan.splt, PID: 4811
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lee.yuchan.splt/com.lee.yuchan.splt.Trans_List}:
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.lee.yuchan.splt.Trans_List.onCreate(Trans_List.java:72)
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)
主要活动 XML
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<include
layout="@layout/app_bar"/>
<TextView
android:id="@+id/selectItems"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/select_instr1"
android:textSize="20sp"
android:gravity="center"
android:paddingTop="4sp"
android:paddingBottom="10sp" >
</TextView>
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1" >
</ListView>
<Button
android:id="@+id/buttonChecked"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="0dip"
android:background="@drawable/custom_button"
android:textColor="#ffffff"
android:text="@string/next_button" />
</LinearLayout>
<!-- The navigation drawer -->
<fragment
android:id="@+id/left_drawer"
android:layout_width="@dimen/nav_dr"
android:layout_height="match_parent"
android:layout_gravity="start"
app:layout="@layout/fragment_navigation_drawer"
android:name="com.lee.yuchan.splt.NavigationDrawerFragment"
tools:layout="@layout/fragment_navigation_drawer" />
</android.support.v4.widget.DrawerLayout>
