Androidスタジオで、私のアプリを起動しようとすると、Androidエミュレータで「My First App has stopped」と表示されます

Question

私はそれがスタックトレースの原因であると考えています。私はここに公式のAndroidアプリのbuldingのチュートリアルをつもりです

：https://developer.android.com/training/index.html

私は「別のアクティビティを開始する」セクションを終えて、それをテストしようとしているときに、このエラーを発見しました。チュートリアルの以前の部分でもアプリを実行できませんでした。このリンクに私を導いた

： What is a stack trace, and how can I use it to debug my application errors?

しかし、私はまだ悩み、それを考え出すを持っています：このリンクに私を導いた

Unfortunately MyApp has stopped. How can I solve this?。これを理解する方法について

12-14 09:52:06.962 3696-3696/com.example.myfirstapp I/zygote:  at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2) 
12-14 09:52:06.962 3696-3696/com.example.myfirstapp I/zygote:  at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:438) 
12-14 09:52:06.962 3696-3696/com.example.myfirstapp I/zygote:  at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:807) 
12-14 09:52:06.962 3696-3696/com.example.myfirstapp D/AndroidRuntime: Shutting down VM 
12-14 09:52:06.964 3696-3696/com.example.myfirstapp E/AndroidRuntime: FATAL EXCEPTION: main 
                     Process: com.example.myfirstapp, PID: 3696 
                     java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.myfirstapp.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/base.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/lib/x86, /system/lib, /vendor/lib]] 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2679) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
                      at android.app.ActivityThread.-wrap11(Unknown Source:0) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
                      at android.os.Handler.dispatchMessage(Handler.java:106) 
                      at android.os.Looper.loop(Looper.java:164) 
                      at android.app.ActivityThread.main(ActivityThread.java:6494) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
                     Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.myfirstapp.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/base.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/lib/x86, /system/lib, /vendor/lib]] 
                      at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125) 
                      at java.lang.ClassLoader.loadClass(ClassLoader.java:379) 
                      at java.lang.ClassLoader.loadClass(ClassLoader.java:312) 
                      at android.app.Instrumentation.newActivity(Instrumentation.java:1174) 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2669) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)  
                      at android.app.ActivityThread.-wrap11(Unknown Source:0)  
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)  
                      at android.os.Handler.dispatchMessage(Handler.java:106)  
                      at android.os.Looper.loop(Looper.java:164)  
                      at android.app.ActivityThread.main(ActivityThread.java:6494)  
                      at java.lang.reflect.Method.invoke(Native Method)  
                      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)  
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)  
                     Suppressed: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/support/v7/app/AppCompatActivity; 
                      at java.lang.VMClassLoader.findLoadedClass(Native Method) 
                      at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:738) 
12-14 09:52:06.964 3696-3696/com.example.myfirstapp E/AndroidRuntime:  at java.lang.ClassLoader.loadClass(ClassLoader.java:363) 
                       ... 12 more 
                     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v7.app.AppCompatActivity" on path: DexPathList[[zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/base.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.myfirstapp-R68LcIdIMck0utpOhrKfsA==/lib/x86, /system/lib, /vendor/lib]] 
                      at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125) 
                      at java.lang.ClassLoader.loadClass(ClassLoader.java:379) 
                      at java.lang.ClassLoader.loadClass(ClassLoader.java:312) 
                       ... 15 more 

任意の提案：ここ

は、エラー・ログの抜粋ですか？ありがとう！

編集：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example.myfirstapp"> 

    <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/AppTheme"> 
     <activity android:name=".MainActivity"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
     <activity android:name=".DisplayMessageActivity" 
      android:parentActivityName=".MainActivity" > 
      <!-- The meta-data tag is required if you support API level 15 and lower --> 
      android:name="android.support.PARENT_ACTIVITY" 
      android:value=".MainActivity" /> 
     </activity> 
    </application> 

</manifest> 

Answer 1

あなたがマニフェストに誤った終了タグがあります：

<activity android:name=".DisplayMessageActivity" 
    android:parentActivityName=".MainActivity" > 
    <!-- The meta-data tag is required if you support API level 15 and lower --> 
    android:name="android.support.PARENT_ACTIVITY" 
    android:value=".MainActivity" /> 
</activity> 

これは、オープンタグのない不正な終了タグであるが、私はこれが私のマニフェストファイルであると考えてい

：

<!-- The meta-data tag is required if you support API level 15 and lower --> 
    android:name="android.support.PARENT_ACTIVITY" 
    android:value=".MainActivity" /> 

取り外してみてください。を更新し

：

チュートリアルから、あなたは<meta-dataのオープンタグを逃しているので、あなたは、オープンタグ追加して、それを修正する必要があります：タグを追加した後

<meta-data android:name="android.support.PARENT_ACTIVITY" android:value=".MainActivity" /> 

を、あなたのコードは次のようになります：

<activity android:name=".DisplayMessageActivity" 
    android:parentActivityName=".MainActivity" > 
    <!-- The meta-data tag is required if you support API level 15 and lower --> 
    <meta-data android:name="android.support.PARENT_ACTIVITY" 
    android:value=".MainActivity" /> 
</activity>