java - Android Manifest Error _ 应用程序无法运行
问题描述
我正在制作一个首先运行 login_nb 的应用程序。在我将 userinfoinput.kt 添加到这个项目之前没有问题,但之后它出现了一些错误。
我的代码清单代码是:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.nb_main">
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.Nb_main"
android:usesCleartextTraffic="true">
<activity android:name=".SignUp" />
<activity android:name=".photoboard" />
<activity android:name=".addPhoto" />
<activity android:name=".textboard" />
<activity android:name=".login_nb">
<intent-filter>
<action android:name="android.intent.action.MAIN" /> <!-- Move this to set the initial activity -->
<category android:name="android.intent.category.LAUNCHER" /> <!-- Move this to set the initial activity -->
</intent-filter>
</activity>
<activity android:name=".popup_color" />
<activity android:name=".built" />
<activity android:name=".userinfoinput"/>
<!--
Set to true if your app is Standalone, that is, it does not require the handheld
app to run.
-->
<activity
android:name=".square"
android:label="@string/title_activity_square" />
<activity android:name=".MainActivity" />
</application>
错误信息如下:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nb_main, PID: 9057
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.nb_main/com.example.nb_main.login_nb}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3194)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.ContextWrapper.getPackageName(ContextWrapper.java:145)
at android.content.ComponentName.<init>(ComponentName.java:131)
at android.content.Intent.<init>(Intent.java:6510)
at com.example.nb_main.login_nb.<init>(login_nb.kt:24)
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:1243)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3182)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
I/Process:发送信号。PID:9057 SIG:9
请告诉我我做错了什么。我主要使用 kotlin,但我也能以某种方式理解 java。
解决方案
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference at android.content.ContextWrapper.getPackageName(ContextWrapper.java:145) at android.content.ComponentName.<init>(ComponentName.java:131) at android.content.Intent.<init>(Intent.java:6510) at com.example.nb_main.login_nb.<init>(login_nb.kt:24)
在login_nb.kt
第 24 行中,有一些实例初始化代码实例化了一个Intent
. 关于活动生命周期还为时过早。在初始化阶段,活动尚未准备好用作Context
. 这种初始化代码的通常位置是活动的onCreate()
.
推荐阅读
- javascript - 如何排列成另一个阵列?
- mysql - 为什么在嵌套查询中创建别名时出现语法错误?
- python - 使用许多多项式的梯度下降不收敛
- laravel - laravel 5.7“找不到类'Maatwebsite\Excel\ExcelServiceProvider'”
- android - 以编程方式克隆 android 应用程序
- javascript - Compare 2 nested arrays to return duplicate arrays
- c# - SetWinEventHook 回调中的 AccessibleObjectFromEvent 调用导致死锁
- python - 运行无限循环并从“外部”(例如 shell 或其他脚本)获取命令
- excel - Excel 等待很长时间才能开始保存文档
- dart - 地图内置列表
到内置列表