Unable to instantiate activity ComponentInfo in android 4.1.2

Question

Hi I'm trying to run my app in a device with android 4.1.2 but I get this error. for some reason my app works fine in android 7.0. In my project I use this library eu.long1.spacetablayout.SpaceTabLayout which I think is the reason for the problem. Please someone help me to resolve this issue.

   java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{maa.myfirstapp/maa.myfirstapp.MainActivity}: java.lang.ClassNotFoundException: maa.myfirstapp.MainActivity
   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2016)
   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2117)
   at android.app.ActivityThread.access$700(ActivityThread.java:134)
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1218)
   at android.os.Handler.dispatchMessage(Handler.java:99)
   at android.os.Looper.loop(Looper.java:137)
   at android.app.ActivityThread.main(ActivityThread.java:4867)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: maa.myfirstapp.MainActivity
   at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
   at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2007)

Manifest.xml

      <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="maa.myfirstapp">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.SET_WALLPAPER"/>
    <uses-permission android:name="android.permission.SET_WALLPAPER_HINTS"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <application
        android:hardwareAccelerated="true"
        android:largeHeap="true"
        tools:replace="android:icon"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:screenOrientation="portrait"
            android:name="maa.myfirstapp.MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:screenOrientation="portrait"
            android:name=".Pop"
            android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" />
    </application>
</manifest>

mainactivity :

package maa.myfirstapp;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import eu.long1.spacetablayout.SpaceTabLayout;
public class MainActivity extends AppCompatActivity {
    SpaceTabLayout tabLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //add the fragments you want to display in a List
        List<Fragment> fragmentList = new ArrayList<>();
        fragmentList.add(new fr1());
        fragmentList.add(new fr2());
        fragmentList.add(new fr3());
        fragmentList.add(new fr4());
        fragmentList.add(new fr5());
        ViewPager viewPager = findViewById(R.id.viewPager);
        tabLayout = findViewById(R.id.spaceTabLayout);
        tabLayout.initialize(viewPager, getSupportFragmentManager(), fragmentList,savedInstanceState);

        /*icon*/
        tabLayout.setTabOneIcon(getResources().getDrawable(R.drawable.a));
        tabLayout.setTabTwoIcon(getResources().getDrawable(R.drawable.qs));
       tabLayout.setTabThreeIcon(getResources().getDrawable(R.drawable.r));
        tabLayout.setTabFourIcon(getResources().getDrawable(R.drawable.an));
        tabLayout.setTabFiveIcon(getResources().getDrawable(R.mipmap.mea));
        /**/


    }
}

Answer 1

我的问题通过在build.gradle中删除此行而解决： multiDexEnabled true

Answer 2

You are missing the package declaration in your MainActivity class. Add the following line at the top of the class:

package maa.myfirstapp;

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