Class not found error, but class definitely exists

Question

OK, so I have a project on Android Studio, but when I run the app on the emulator, it crashes. In the stack trace, there is a class not found exception for the main activity class, and by my understanding it points to a line with merely a closing brace for an if statement.

Here is the stack trace:

02-21 14:49:44.498    2362-2362/com.example.user.assignment1 E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.user.assignment1, PID: 2362 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.user.assignment1/com.example.user.assignment1.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.user.assignment1.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.user.assignment1-2/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)         at android.app.ActivityThread.access$800(ActivityThread.java:144)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)         at android.os.Handler.dispatchMessage(Handler.java:102)         at android.os.Looper.loop(Looper.java:135)         at android.app.ActivityThread.main(ActivityThread.java:5221)         at java.lang.reflect.Method.invoke(Native Method)         at java.lang.reflect.Method.invoke(Method.java:372)         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)  Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.user.assignment1.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.user.assignment1-2/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]         at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)         at java.lang.ClassLoader.loadClass(ClassLoader.java:511)         at java.lang.ClassLoader.loadClass(ClassLoader.java:469)         at android.app.Instrumentation.newActivity(Instrumentation.java:1065)         at   android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at     com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Suppressed: java.lang.NoClassDefFoundError: com.example.user.assignment1.MainActivity         at dalvik.system.DexFile.defineClassNative(Native Method)         at dalvik.system.DexFile.defineClass(DexFile.java:226)         at dalvik.system.DexFile.loadClassBinaryName(DexFile.java:219)         at dalvik.system.DexPathList.findClass(DexPathList.java:321)         at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:54)         ... 14 more Suppressed: java.lang.ClassNotFoundException: com.example.user.assignment1.MainActivity         at java.lang.Class.classForName(Native Method)         at java.lang.BootClassLoader.findClass(ClassLoader.java:781)         at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)         at java.lang.ClassLoader.loadClass(ClassLoader.java:504)         ... 13 more  Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available 

Since I cannot figure out where the error is, I'm going to post the code here as well:

package com.example.user.assignment1;  import android.support.v7.app.ActionBarActivity; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.Button; import android.widget.TextView;  import java.util.Random;   public class MainActivity extends ActionBarActivity {  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main); }   @Override public boolean onCreateOptionsMenu(Menu menu) {     // Inflate the menu; this adds items to the action bar if it is present.     getMenuInflater().inflate(R.menu.menu_main, menu);     return true; }  @Override public boolean onOptionsItemSelected(MenuItem item) {     // Handle action bar item clicks here. The action bar will     // automatically handle clicks on the Home/Up button, so long     // as you specify a parent activity in AndroidManifest.xml.     int id = item.getItemId();      //noinspection SimplifiableIfStatement     if (id == R.id.action_settings) {         return true;     }      return super.onOptionsItemSelected(item); }  public void left_click(View view) {     Button l=(Button) findViewById(R.id.left);     Button r=(Button) findViewById(R.id.right);     int l1 = Integer.parseInt(l.getText().toString());     int r1 = Integer.parseInt(r.getText().toString());     TextView t=(TextView) findViewById(R.id.label);         if(l1>r1)     {         t.setText("Correct! "+l1+" is bigger!");     }     else     {         t.setText("Sorry! " + r1 + " is bigger!");     }      Random ran = new Random();     int random = ran.nextInt(100);      l.setText(random);     r.setText(random);  }  public void right_click(View view) {     Button l=(Button) findViewById(R.id.left);     Button r=(Button) findViewById(R.id.right);     int l1 = Integer.parseInt(l.getText().toString());     int r1 = Integer.parseInt(r.getText().toString());     TextView t=(TextView) findViewById(R.id.label);         if(l1<r1)     {         t.setText("Correct! "+r1+" is bigger!");     }     else     {         t.setText("Sorry! " + l1 + " is bigger!");     }     Random ran = new Random();     int random = ran.nextInt(100);      l.setText(random);     r.setText(random); } } 

On the ActivityThread.java file, there are many errors which all seem to rise from errors in imports. The imports with errors for that file are:

import android.content.IIntentReceiver;//IIntentReceiver is in red import android.content.pm.IPackageManager;//IPackageManager is in red import android.net.IConnectivityManager;//IConnectivityManager is in red import com.android.internal.app.IVoiceInteractor;//IVoiceInteractor import com.android.org.conscrypt.OpenSSLSocketImpl;//conscrypt is in red import com.android.org.conscrypt.TrustedCertificateStore;//conscrypt is in red import com.google.android.collect.Lists;//google is in red import libcore.io.DropBox;//libcore is in red import libcore.io.EventLogger;//libcore is in red import libcore.io.IoUtils;//libcore is in red import libcore.net.event.NetworkEventDispatcher;//libcore is in red import dalvik.system.CloseGuard;//CloseGuard is in red import dalvik.system.VMDebug;//VMDebug is in red import dalvik.system.VMRuntime;//VMRuntime is in red 

And here's the manifest file as requested:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.user.assignment1" >  <application     android:allowBackup="true"     android:icon="@drawable/ic_launcher"     android:label="@string/app_name"     android:theme="@style/AppTheme" >     <activity         android:name=".MainActivity"         android:label="@string/app_name" >         <intent-filter>             <action android:name="android.intent.action.MAIN" />              <category android:name="android.intent.category.LAUNCHER" />         </intent-filter>     </activity> </application> 

And the build.gradle file:

apply plugin: 'com.android.application'  android { compileSdkVersion 21 buildToolsVersion "21.1.2"  defaultConfig {     applicationId "com.example.user.assignment1"     minSdkVersion 8     targetSdkVersion 21     versionCode 1     versionName "1.0" } buildTypes {     release {         minifyEnabled false         proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'     } } }  dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile 'com.android.support:appcompat-v7:21.0.3' } 

And the gradle build for the project:

// Top-level build file where you can add configuration options common to all sub-projects/modules.  buildscript { repositories {     jcente     dependencies {         classpath 'com.android.tools.build:gradle:1.0.0'          // NOTE: Do not place your application dependencies here; they belong         // in the individual module build.gradle files     } }  allprojects {     repositories {         jcenter()     } } r() } 

Answer 1

At first "Clean" and "Sync Project with Gradle Files". Then run your code.