RuntimeException：无法实例化活动组件信息 Android

Question

I'm trying to code something in android but I can't get it working on my external device. It always force quits. I've coded one or two things in android and I was always able to launch them, so I have no idea where this error is coming from.

This is the code of the launcher activity:

package x.y.alarm;

import java.util.ArrayList;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends ActionBarActivity {

    final int setAlarm = 214;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button add = (Button) findViewById(R.id.add);
        add.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                startActivityForResult(new Intent(MainActivity.this,AlarmScreen.class), setAlarm);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data){
        if(requestCode == setAlarm){
            if(resultCode == RESULT_OK){
                String name = data.getStringExtra("Name");
                String time = data.getStringExtra("Time");  //In h:m format
                String days = data.getStringExtra("Days");  //Seperated by ;

                String[] t = time.split(":");
                String[] d = days.split(";");

                int[] hrsAndMin = new int[t.length];
                for(int i = 0; i < t.length; i++){
                    hrsAndMin[i] = Integer.parseInt(t[i]);
                }

                ArrayList<Day> ds = new ArrayList<Day>();
                for(int i = 0; i < d.length; i++){
                    switch(d[i]){
                    case("Monday"):
                        ds.add(Day.Monday);
                    case("Tuesday"):
                        ds.add(Day.Tuesday);
                    case("Wednesday"):
                        ds.add(Day.Wednesday);
                    case("Thursday"):
                        ds.add(Day.Thursday);
                    case("Friday"):
                        ds.add(Day.Friday);
                    case("Saturday"):
                        ds.add(Day.Saturday);
                    case("Sunday"):
                        ds.add(Day.Sunday);
                    }
                }

                Alarm alarm = new Alarm(name, hrsAndMin[0], hrsAndMin[1] , Status.ON, ds);

                addAlarm(alarm);
            }
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void addAlarm(Alarm alarm){

    }
}

This is the AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="sander.bylemans.alarm"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="sander.bylemans.alarm.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>
        <activity
            android:name="sander.bylemans.alarm.AlarmScreen"
            android:label="@string/title_activity_alarm_screen" >
        </activity>
    </application>

</manifest>

And this is the error I receive and I don't know how to resolve:

10-27 20:56:52.278: W/dalvikvm(14367): Unable to resolve superclass of Lsander/bylemans/alarm/MainActivity; (4)
10-27 20:56:52.278: W/dalvikvm(14367): Link of class 'Lsander/bylemans/alarm/MainActivity;' failed
10-27 20:56:52.298: W/dalvikvm(14367): threadid=1: thread exiting with uncaught exception (group=0x4001d560)
10-27 20:56:52.398: E/AndroidRuntime(14367): FATAL EXCEPTION: main
10-27 20:56:52.398: E/AndroidRuntime(14367): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{sander.bylemans.alarm/sander.bylemans.alarm.MainActivity}: java.lang.ClassNotFoundException: sander.bylemans.alarm.MainActivity in loader dalvik.system.PathClassLoader[/data/app/sander.bylemans.alarm-2.apk]
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1573)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.os.Handler.dispatchMessage(Handler.java:99)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.os.Looper.loop(Looper.java:130)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread.main(ActivityThread.java:3687)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at java.lang.reflect.Method.invokeNative(Native Method)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at java.lang.reflect.Method.invoke(Method.java:507)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at dalvik.system.NativeStart.main(Native Method)
10-27 20:56:52.398: E/AndroidRuntime(14367): Caused by: java.lang.ClassNotFoundException: sander.bylemans.alarm.MainActivity in loader dalvik.system.PathClassLoader[/data/app/sander.bylemans.alarm-2.apk]
10-27 20:56:52.398: E/AndroidRuntime(14367):    at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
10-27 20:56:52.398: E/AndroidRuntime(14367):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1565)
10-27 20:56:52.398: E/AndroidRuntime(14367):    ... 11 more

I searched a long time for a solution and can't seem to find one that solves the problem. I tried different things but none of them work. If someone could help me I would be forever thankfull.

Greets

Answer 1

VM is not able to find android.support.v7.app.ActionBarActivity; Check the location of your support library jar. It should be in project's libs folder to work

Answer 2

It seems that the needed jar is not in your libs folder. Copy the jar to your libs folder

You need to make sure that the lib is checked in the following path

Go to Properties->Java Build Path->Order and Export and make sure the library is checked.