java - 工具栏上的 Android RoboGuice 3.0 空指针

Question

我做了一个 Activity ，想使用 Roboguice 注入(inject)我的工具栏，但我得到了 Nullpointer 异常。尝试了一些解决方案，但它们不起作用。这是我的进度。

MainActivity.java

@ContentView(R.layout.activity_main)
public class MainActivity extends RoboActionBarActivity {
    @InjectView(R.id.tool_bar)
    Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setSupportActionBar(toolbar);
    }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".activities.MainActivity">

    <include
        android:id="@+id/tool_bar"
        layout="@layout/tool_bar" />
    <FrameLayout
        android:layout_below="@+id/tool_bar"
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".activities.MainActivity"
        tools:ignore="MergeRootFrame" />
</RelativeLayout>

list .xml

  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        package="com.android.app">
        <application
            android:name=".application.CustomApplication"
            android:allowBackup="true"
            android:icon="@mipmap/ic_launcher"
            android:label="@string/app_name"
            android:supportsRtl="true"
            android:theme="@style/AppTheme"
            tools:replace="android:icon">
            <meta-data
                android:name="roboguice.annotations.packages"
                android:value="roboguice,databasename" />
            <activity android:name=".activities.MainActivity">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>
    </manifest>

CustomApplication.java

    public class CustomApplication extends Application {
    public void onCreate() {
        super.onCreate();
        RoboGuice.setUseAnnotationDatabases(false);
    }
}

Module.gradle

 compile 'org.roboguice:roboguice:3.+'
 provided 'org.roboguice:roboblender:3.+'

App.gradle

allprojects {
    gradle.projectsEvaluated {
        tasks.withType(JavaCompile) {
            options.compilerArgs << "-AguiceAnnotationDatabasePackageName=databasename"
        }
    }
    repositories {
        jcenter()
    }
}

有错误的日志

FATAL EXCEPTION: main
                                                                     Process: com.android.jammboree, PID: 4817
                                                                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.app/com.android.app.activities.MainActivity}: java.lang.NullPointerException
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
                                                                         at android.app.ActivityThread.access$800(ActivityThread.java:135)
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                         at android.os.Looper.loop(Looper.java:136)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:5001)
                                                                         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:785)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
                                                                         at dalvik.system.NativeStart.main(Native Method)
                                                                      Caused by: java.lang.NullPointerException
                                                                         at android.support.v7.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:98)
                                                                         at android.support.v7.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:91)
                                                                         at android.support.v7.app.ToolbarActionBar.<init>(ToolbarActionBar.java:73)
                                                                         at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:205)
                                                                         at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:99)
                                                                         at com.android.jammboree.activities.MainActivity.onCreate(MainActivity.java:24)
                                                                         at android.app.Activity.performCreate(Activity.java:5231)
                                                                         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
                                                                         at android.app.ActivityThread.access$800(ActivityThread.java:135) 
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                         at android.os.Looper.loop(Looper.java:136) 
                                                                         at android.app.ActivityThread.main(ActivityThread.java:5001) 
                                                                         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:785) 
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
                                                                         at dalvik.system.NativeStart.main(Native Method) 

Answer 1

NullPointerException is thrown when an application attempts to use an object reference, having the null value.

像这样在 Toolbar xml 中调用 id 属性:

<?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"
    android:id="@+id/tool_bar"
     >
</android.support.v7.widget.Toolbar>

然后将其从 include block 中删除，如下所示:

<include
    android:id="@+id/tool_bar"    // No need 
    layout="@layout/tool_bar" />

然后

@InjectView(R.id.tool_bar)
Toolbar toolbar;