android - 运行android示例代码时无法实例化 Activity 组件

Question

我正在学习 tutorial从安卓网站。

但是当我运行应用程序时，它提示Unable to instantiate activity component，关于classNotFoundException。但是在 manifext.xml 文件中注册了 MainActivity。我不知道问题出在哪里。这是完整的错误日志。

05-03 18:59:00.425: E/AndroidRuntime(20858): FATAL EXCEPTION: main
05-03 18:59:00.425: E/AndroidRuntime(20858): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.effectivenavigation/com.example.android.effectivenavigation.MainActivity}: java.lang.ClassNotFoundException: com.example.android.effectivenavigation.MainActivity
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread.access$600(ActivityThread.java:130)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.os.Looper.loop(Looper.java:137)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread.main(ActivityThread.java:4745)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at java.lang.reflect.Method.invokeNative(Native Method)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at java.lang.reflect.Method.invoke(Method.java:511)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at dalvik.system.NativeStart.main(Native Method)
05-03 18:59:00.425: E/AndroidRuntime(20858): Caused by: java.lang.ClassNotFoundException: com.example.android.effectivenavigation.MainActivity
05-03 18:59:00.425: E/AndroidRuntime(20858):    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
05-03 18:59:00.425: E/AndroidRuntime(20858):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
05-03 18:59:00.425: E/AndroidRuntime(20858):    ... 11 more

list 文件，AbdroidManifest.xml

<!--
  Copyright 2012 The Android Open Source Project

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  -->

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.effectivenavigation"
    android:versionCode="1"
    android:versionName="1.0">

    <uses-sdk android:minSdkVersion="14" />

    <application android:label="@string/app_name"
        android:icon="@drawable/ic_launcher"
        android:theme="@android:style/Theme.Holo.Light.DarkActionBar">

        <activity android:name=".MainActivity" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name=".CollectionDemoActivity" android:label="@string/demo_collection" />

    </application>
</manifest>

Answer 1

如果我没记错的话，您正在使用 Android 支持库。你是如何将它添加到你的项目中的？如果您在 Java Build Path 中添加，您可能会遇到此异常。

一个建议是从您的构建路径中删除 JAR，然后右键单击您的项目并选择 Android Tools --> Add Support Library。