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好的，所以我有我的 Android 应用程序，它不会以“无法实例化活动 ComponentInfo{}”错误启动，基本上我的清单文件中有问题，不会让应用程序启动第一个活动。我创建了一个新的但本质上是重复的项目（手动复制 Java+XML 代码用于 Main、第二个 + 第三个“测试人员”活动，当然还有字符串）。我保留了新项目的清单，但为测试人员添加了活动行。我希望所有东西基本上都是库存，所以什么都不会出错，什么也没做，应用程序加载到模拟器和我的手机上就可以了。

因此，我将新清单复制到我的旧项目中以“默认”它，然后我复制并粘贴了已经存在并且可以工作的测试器活动代码，用于其他 3 个活动。突然不想工作了。一切都在那里，但有什么问题？（注意可绘制的图标已更改，但这与它无关）。所有活动名称都与包名称匹配。这可能是一个错误吗？老实说，我找不到任何问题。

重复（+工作）代码

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/logo3"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.ollygrov.bakerspride.Main"
        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="com.ollygrov.bakerspride.Cal"
        android:label="@string/title_activity_cal" >
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Breads"
        android:label="@string/title_activity_breads" >
    </activity>
</application>

旧（+ 不工作）代码

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.ollygrov.bakerspride.Main"
        android:label="@string/app_title" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Cal"
        android:label="@string/title_activity_cal" >
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Breads"
        android:label="@string/title_activity_breads" >
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Gal"
        android:label="@string/title_activity_gal" >
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Tut"
        android:label="@string/title_activity_tut" >
    </activity>
    <activity
        android:name="com.ollygrov.bakerspride.Rec"
        android:label="@string/title_activity_rec" >
    </activity>
 </application>

编辑：我刚刚将代码复制并粘贴到 Chrome 上的搜索栏中（更改 droid:icon 和 droid:label 以适应），它们完全相同！什么？！我不允许有 6 项活动之类的吗？

错误：

09-04 11:33:04.895: E/AndroidRuntime(717): FATAL EXCEPTION: main
09-04 11:33:04.895: E/AndroidRuntime(717): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.ollygrov.bakerspride/com.ollygrov.bakerspride.Main}: java.lang.NullPointerException
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.os.Looper.loop(Looper.java:137)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread.main(ActivityThread.java:4745)
09-04 11:33:04.895: E/AndroidRuntime(717):  at java.lang.reflect.Method.invokeNative(Native Method)
09-04 11:33:04.895: E/AndroidRuntime(717):  at java.lang.reflect.Method.invoke(Method.java:511)
09-04 11:33:04.895: E/AndroidRuntime(717):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-04 11:33:04.895: E/AndroidRuntime(717):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-04 11:33:04.895: E/AndroidRuntime(717):  at dalvik.system.NativeStart.main(Native Method)
09-04 11:33:04.895: E/AndroidRuntime(717): Caused by: java.lang.NullPointerException
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.Activity.findViewById(Activity.java:1825)
09-04 11:33:04.895: E/AndroidRuntime(717):  at com.ollygrov.bakerspride.Main.<init>(Main.java:19)
09-04 11:33:04.895: E/AndroidRuntime(717):  at java.lang.Class.newInstanceImpl(Native Method)
09-04 11:33:04.895: E/AndroidRuntime(717):  at java.lang.Class.newInstance(Class.java:1319)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
09-04 11:33:04.895: E/AndroidRuntime(717):  ... 11 more
09-04 11:34:58.665: E/Trace(765): error opening trace file: No such file or directory (2)
09-04 11:34:59.095: D/AndroidRuntime(765): Shutting down VM
09-04 11:34:59.095: W/dalvikvm(765): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-04 11:34:59.114: E/AndroidRuntime(765): FATAL EXCEPTION: main
09-04 11:34:59.114: E/AndroidRuntime(765): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.ollygrov.bakerspride/com.ollygrov.bakerspride.Main}: java.lang.NullPointerException
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.os.Looper.loop(Looper.java:137)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread.main(ActivityThread.java:4745)
09-04 11:34:59.114: E/AndroidRuntime(765):  at java.lang.reflect.Method.invokeNative(Native Method)
09-04 11:34:59.114: E/AndroidRuntime(765):  at java.lang.reflect.Method.invoke(Method.java:511)
09-04 11:34:59.114: E/AndroidRuntime(765):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-04 11:34:59.114: E/AndroidRuntime(765):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-04 11:34:59.114: E/AndroidRuntime(765):  at dalvik.system.NativeStart.main(Native Method)
09-04 11:34:59.114: E/AndroidRuntime(765): Caused by: java.lang.NullPointerException
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.Activity.findViewById(Activity.java:1825)
09-04 11:34:59.114: E/AndroidRuntime(765):  at com.ollygrov.bakerspride.Main.<init>(Main.java:19)
09-04 11:34:59.114: E/AndroidRuntime(765):  at java.lang.Class.newInstanceImpl(Native Method)
09-04 11:34:59.114: E/AndroidRuntime(765):  at java.lang.Class.newInstance(Class.java:1319)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-04 11:34:59.114: E/AndroidRuntime(765):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
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1 回答 1

1

问题是你的Main构造函数：

09-04 11:33:04.895: E/AndroidRuntime(717): Caused by: java.lang.NullPointerException
09-04 11:33:04.895: E/AndroidRuntime(717):  at android.app.Activity.findViewById(Activity.java:1825)
09-04 11:33:04.895: E/AndroidRuntime(717):  at com.ollygrov.bakerspride.Main.<init>(Main.java:19)

在第 19 行中，Main.java你们试图打电话findViewById()，这显然是行不通的。在构造函数中调用此类代码是一种过早的方法。我最好的猜测是，您需要将所有内容从 cronstructor 移至onCreate()Activity。

通常，您不需要在活动或片段中使用自定义构造函数。

于 2013-09-05T10:50:17.393 回答