安卓:裸码扫描程序在应用程序启动时崩溃

Question

我试图编写一个裸代码扫描程序应用程序。我在YouTube上找到了这个[视频][1]，解释得很好。我已经完全完成了此视频中的内容，但是当我编译时，应用程序崩溃了。我试图在谷歌上找到错误，但我没有解决方案。我尝试了一些事情，例如

File -> Invalidate Cache and restart

但仍然不起作用。

我是安卓新手。 你能帮我解决这个问题吗？

这是我的build.gradle：

apply plugin: 'com.android.application'
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.noums.qrcodereader"
minSdkVersion 15
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'android.arch.navigation:navigation-fragment:1.0.0-alpha06'
implementation 'android.arch.navigation:navigation-ui:1.0.0-alpha06'
implementation 'com.android.support:design:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation 'com.google.android.gms:play-services:12.0.1'
}

在build.gradle文件中，我有这个错误： [![在此输入图像描述][2]][2] 这是我的运行日志：

10/13 02:51:52: Launching app
$ adb install-multiple -r -t /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/dep/dependencies.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_5.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_6.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_0.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_1.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_4.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_3.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_2.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_8.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_7.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/split-apk/debug/slices/slice_9.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/resources/instant-run/debug/resources-debug.apk /home/user/AndroidStudioProjects/QRcodeReader/app/build/intermediates/instant-run-apk/debug/app-debug.apk 
Split APKs installed in 4 s 491 ms
$ adb shell am start -n "com.noums.qrcodereader/com.noums.qrcodereader.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Client not ready yet..Waiting for process to come online
Connected to process 31525 on device oneplus-oneplus_a5010-d3691788
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
I/zygote64: Late-enabling -Xcheck:jni
I/zygote64: The ClassLoaderContext is a special shared library.
I/FirebaseInitProvider: FirebaseApp initialization unsuccessful
I/InstantRun: starting instant run server: is main process
I/zygote64: Rejecting re-init on previously-failed class java.lang.Class<android.support.v4.view.ViewCompat$OnUnhandledKeyEventListenerWrapper>: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/view/View$OnUnhandledKeyEventListener;
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.View$OnUnhandledKeyEventListener" on path: DexPathList[[zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/base.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_dependencies_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_resources_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.noums.qrcode
at java.lang.Class dalvik.system.BaseDexClassLoader.findClass(java.lang.String) (BaseDexClassLoader.java:125)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String, boolean) (ClassLoader.java:379)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String) (ClassLoader.java:312)
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
Rejecting re-init on previously-failed class java.lang.Class<android.support.v4.view.ViewCompat$OnUnhandledKeyEventListenerWrapper>: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/view/View$OnUnhandledKeyEventListener;
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.View$OnUnhandledKeyEventListener" on path: DexPathList[[zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/base.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_dependencies_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_resources_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.noums.qrcode
at java.lang.Class dalvik.system.BaseDexClassLoader.findClass(java.lang.String) (BaseDexClassLoader.java:125)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String, boolean) (ClassLoader.java:379)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String) (ClassLoader.java:312)
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
Rejecting re-init on previously-failed class java.lang.Class<android.support.v4.view.ViewCompat$OnUnhandledKeyEventListenerWrapper>: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/view/View$OnUnhandledKeyEventListener;
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.View$OnUnhandledKeyEventListener" on path: DexPathList[[zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/base.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_dependencies_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_resources_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.noums.qrcodereader-9oqdGKRhlKrW2VVgy_xxtA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.noums.qrcode
at java.lang.Class dalvik.system.BaseDexClassLoader.findClass(java.lang.String) (BaseDexClassLoader.java:125)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String, boolean) (ClassLoader.java:379)
at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String) (ClassLoader.java:312)
at void android.support.v4.view.ViewCompat.setOnApplyWindowInsetsListener(android.view.View, android.support.v4.view.OnApplyWindowInsetsListener) (ViewCompat.java:2203)
at android.view.ViewGroup android.support.v7.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:637)
at void android.support.v7.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:518)
at void android.support.v7.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:466)
at void android.support.v7.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:140)
at void com.noums.qrcodereader.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:33)
at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7041)
at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7032)
at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1231)
at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2864)
at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2989)
at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1688)
at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
at void android.os.Looper.loop() (Looper.java:164)
at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6753)
at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:482)
at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807)
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.noums.qrcodereader, PID: 31525
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.noums.qrcodereader/com.noums.qrcodereader.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2911)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2989)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1688)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6753)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:482)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.noums.qrcodereader.MainActivity.onCreate(MainActivity.java:50)
at android.app.Activity.performCreate(Activity.java:7041)
at android.app.Activity.performCreate(Activity.java:7032)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1231)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2864)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2989) 
at android.app.ActivityThread.-wrap11(Unknown Source:0) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1688) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:164) 
at android.app.ActivityThread.main(ActivityThread.java:6753) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:482) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
W/OPDiagnose: getService:OPDiagnoseService NULL
D/OSTracker: OS Event: crash
D/AbstractTracker: Event success
Application terminated.

Answer 1

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.noums.qrcodereader.MainActivity.onCreate(MainActivity.java:50)

这看起来像 MainActivity.java 文件第 50 行的空引用。