Android 配置 之 AndroidManifest.xml 出错 Unable to instantiate activity ComponentInfo

本文详细解析了在Android应用中遇到的一个常见问题:由于配置错误导致的活动启动异常。问题出现在尝试启动一个名为GestureEvent的活动时,由于在清单文件中配置的活动名称不正确而引发异常。

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04-08 18:17:48.468: ERROR/AndroidRuntime(20955): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example/com.example.demo.GestureEvent}: java.lang.ClassNotFoundException: com.example.demo.GestureEvent in loader dalvik.system.PathClassLoader@4485c9a8

04-08 18:17:48.468: ERROR/AndroidRuntime(20955): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2497)

(ZygoteInit.java:618)

.............

============================

响应的配置文件

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example" android:versionCode="1" android:versionName="1.0"> <uses-sdk android:minSdkVersion="7" /> <application android:icon="@drawable/icon" android:label="helloworld"> <activity android:name=".demo.GestureEvent">//error <activity android:name="com.android.demo.GestureEvent">//right <intent-filter> <action android:name="android.intent.action.MAIN"></action> <category android:name="android.intent.category.LAUNCHER"></category> </intent-filter> </activity> </application> </manifest>

关键代码

<activity android:name=".demo.GestureEvent">

对于 action 为MAIN 且 category 为LAUNCHER 的

且 与所指定的 package="com.example" 不一致的activity 来说

-----------------------------------------------------

android:name 需要配置成 全路径

<activity android:name="com.android.demo.GestureEvent">

否则将会抛出如上异常

分析以下报错信息: E FATAL EXCEPTION: main Process: com.example.contacts2, PID: 11798 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.contacts2/com.example.contacts2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4186) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4467) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:222) at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:133) at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:103) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:80) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2823) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loopOnce(Looper.java:248) at android.os.Looper.loop(Looper.java:338) at android.app.ActivityThread.main(ActivityThread.java:9067) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:593) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:932) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:208) at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:174) at android.content.Context.obtainStyledAttributes(Context.java:1103) at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:922) at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:889) at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:691) at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:264) at com.example.contacts2.MainActivity.<init>(MainActivity.java:35) at java.lang.Class.newInstance(Native Method) at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95) at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45) at android.app.Instrumentation.newActivity(Instrumentation.java:1443) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4173) ... 13 more
07-23
分析以下报错; FATAL EXCEPTION: main Process: com.example.contacts2, PID: 12148 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.contacts2/com.example.contacts2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4186) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4467) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:222) at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:133) at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:103) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:80) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2823) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loopOnce(Looper.java:248) at android.os.Looper.loop(Looper.java:338) at android.app.ActivityThread.main(ActivityThread.java:9067) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:593) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:932) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:208) at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:174) at android.content.Context.obtainStyledAttributes(Context.java:1103) at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:922) at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:889) at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:691) at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:264) at com.example.contacts2.MainActivity.<init>(MainActivity.java:36) at java.lang.Class.newInstance(Native Method) at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95) at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45) at android.app.Instrumentation.newActivity(Instrumentation.java:1443) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4173) ... 13 more
07-23
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