Q:

how to solve unable to instantiate activity with google play service?

i follow this tutorial : http://www.androidhive.info/2014/02/android-login-with-google-plus-account-1/
but i always get this error

08-28 23:37:38.557: E/AndroidRuntime(28591): java.lang.RuntimeException: Unable to instantiate activity
  ComponentInfo{com.foo.app/com.foo.app.LoginActivity}:
  java.lang.ClassNotFoundException: Didn't find class
  "com.foo.app.LoginActivity" on path: DexPathList[[zip file
  "/data/app/com.foo.app-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.foo.app-2,
  /vendor/lib, /system/lib]]

why this happend? and how to solve this?
this only happend if i navigate to activity with google play service imported
manifest :
<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="14" />

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />

    <activity
        android:name="com.foo.app.SplashActivity"
        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="com.foo.app.LoginActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="com.foo.app.Login" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
</application>

LoginActivity.java
package com.foo.app;

import java.io.InputStream;

import android.app.Activity;
import android.content.Intent;
import android.content.IntentSender.SendIntentException;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.plus.Plus;
import com.google.android.gms.plus.model.people.Person;

public class LoginActivity extends Activity implements OnClickListener, ConnectionCallbacks, OnConnectionFailedListener {

    private static final int RC_SIGN_IN = 0;
    // Logcat tag
    private static final String TAG = "MainActivity";

    // Profile pic image size in pixels
    private static final int PROFILE_PIC_SIZE = 400;

    // Google client to interact with Google API
    private GoogleApiClient mGoogleApiClient;

    /**
     * A flag indicating that a PendingIntent is in progress and prevents us
     * from starting further intents.
     */
    private boolean mIntentInProgress;

    private boolean mSignInClicked;

    private ConnectionResult mConnectionResult;

    private SignInButton btnSignIn;
    private Button btnSignOut, btnRevokeAccess;
    private ImageView imgProfilePic;
    private TextView txtName, txtEmail;
    private LinearLayout llProfileLayout;

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        btnSignIn = (SignInButton) findViewById(R.id.btn_sign_in);
        btnSignOut = (Button) findViewById(R.id.btn_sign_out);
        btnRevokeAccess = (Button) findViewById(R.id.btn_revoke_access);
        imgProfilePic = (ImageView) findViewById(R.id.imgProfilePic);
        txtName = (TextView) findViewById(R.id.txtName);
        txtEmail = (TextView) findViewById(R.id.txtEmail);
        llProfileLayout = (LinearLayout) findViewById(R.id.llProfile);

        // Button click listeners
        btnSignIn.setOnClickListener(this);
        btnSignOut.setOnClickListener(this);
        btnRevokeAccess.setOnClickListener(this);

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this).addApi(Plus.API)
                .addScope(Plus.SCOPE_PLUS_LOGIN).build();

    }

    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }

    protected void onStop() {
        super.onStop();
        if (mGoogleApiClient.isConnected()) {
            mGoogleApiClient.disconnect();
        }
    }

    /**
     * Method to resolve any signin errors
     * */
    private void resolveSignInError() {
        if (mConnectionResult.hasResolution()) {
            try {
                mIntentInProgress = true;
                mConnectionResult.startResolutionForResult(this, RC_SIGN_IN);
            } catch (SendIntentException e) {
                mIntentInProgress = false;
                mGoogleApiClient.connect();
            }
        }
    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {
        if (!result.hasResolution()) {
            GooglePlayServicesUtil.getErrorDialog(result.getErrorCode(), this,
                    0).show();
            return;
        }

        if (!mIntentInProgress) {
            // Store the ConnectionResult for later usage
            mConnectionResult = result;

            if (mSignInClicked) {
                // The user has already clicked 'sign-in' so we attempt to
                // resolve all
                // errors until the user is signed in, or they cancel.
                resolveSignInError();
            }
        }

    }

    @Override
    protected void onActivityResult(int requestCode, int responseCode,
            Intent intent) {
        if (requestCode == RC_SIGN_IN) {
            if (responseCode != RESULT_OK) {
                mSignInClicked = false;
            }

            mIntentInProgress = false;

            if (!mGoogleApiClient.isConnecting()) {
                mGoogleApiClient.connect();
            }
        }
    }

    @Override
    public void onConnected(Bundle arg0) {
        mSignInClicked = false;
        Toast.makeText(this, "User is connected!", Toast.LENGTH_LONG).show();

        // Get user's information
        getProfileInformation();

        // Update the UI after signin
        updateUI(true);

    }

    /**
     * Updating the UI, showing/hiding buttons and profile layout
     * */
    private void updateUI(boolean isSignedIn) {
        if (isSignedIn) {
            btnSignIn.setVisibility(View.GONE);
            btnSignOut.setVisibility(View.VISIBLE);
            btnRevokeAccess.setVisibility(View.VISIBLE);
            llProfileLayout.setVisibility(View.VISIBLE);
        } else {
            btnSignIn.setVisibility(View.VISIBLE);
            btnSignOut.setVisibility(View.GONE);
            btnRevokeAccess.setVisibility(View.GONE);
            llProfileLayout.setVisibility(View.GONE);
        }
    }

    /**
     * Fetching user's information name, email, profile pic
     * */
    private void getProfileInformation() {
        try {
            if (Plus.PeopleApi.getCurrentPerson(mGoogleApiClient) != null) {
                Person currentPerson = Plus.PeopleApi
                        .getCurrentPerson(mGoogleApiClient);
                String personName = currentPerson.getDisplayName();
                String personPhotoUrl = currentPerson.getImage().getUrl();
                String personGooglePlusProfile = currentPerson.getUrl();
                String email = Plus.AccountApi.getAccountName(mGoogleApiClient);

                Log.e(TAG, "Name: " + personName + ", plusProfile: "
                        + personGooglePlusProfile + ", email: " + email
                        + ", Image: " + personPhotoUrl);

                txtName.setText(personName);
                txtEmail.setText(email);

                // by default the profile url gives 50x50 px image only
                // we can replace the value with whatever dimension we want by
                // replacing sz=X
                personPhotoUrl = personPhotoUrl.substring(0,
                        personPhotoUrl.length() - 2)
                        + PROFILE_PIC_SIZE;

                new LoadProfileImage(imgProfilePic).execute(personPhotoUrl);

            } else {
                Toast.makeText(getApplicationContext(),
                        "Person information is null", Toast.LENGTH_LONG).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onConnectionSuspended(int arg0) {
        mGoogleApiClient.connect();
        updateUI(false);
    }

    @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;
    }

    /**
     * Button on click listener
     * */
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.btn_sign_in:
            // Signin button clicked
            signInWithGplus();
            break;
        case R.id.btn_sign_out:
            // Signout button clicked
            signOutFromGplus();
            break;
        case R.id.btn_revoke_access:
            // Revoke access button clicked
            revokeGplusAccess();
            break;
        }
    }

    /**
     * Sign-in into google
     * */
    private void signInWithGplus() {
        if (!mGoogleApiClient.isConnecting()) {
            mSignInClicked = true;
            resolveSignInError();
        }
    }

    /**
     * Sign-out from google
     * */
    private void signOutFromGplus() {
        if (mGoogleApiClient.isConnected()) {
            Plus.AccountApi.clearDefaultAccount(mGoogleApiClient);
            mGoogleApiClient.disconnect();
            mGoogleApiClient.connect();
            updateUI(false);
        }
    }

    /**
     * Revoking access from google
     * */
    private void revokeGplusAccess() {
        if (mGoogleApiClient.isConnected()) {
            Plus.AccountApi.clearDefaultAccount(mGoogleApiClient);
            Plus.AccountApi.revokeAccessAndDisconnect(mGoogleApiClient)
                    .setResultCallback(new ResultCallback<Status>() {
                        @Override
                        public void onResult(Status arg0) {
                            Log.e(TAG, "User access revoked!");
                            mGoogleApiClient.connect();
                            updateUI(false);
                        }

                    });
        }
    }

    /**
     * Background Async task to load user profile picture from url
     * */
    private class LoadProfileImage extends AsyncTask<String, Void, Bitmap> {
        ImageView bmImage;

        public LoadProfileImage(ImageView bmImage) {
            this.bmImage = bmImage;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            bmImage.setImageBitmap(result);
        }
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".LoginActivity" >

    <LinearLayout
        android:id="@+id/llProfile"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp"
        android:orientation="horizontal"
        android:weightSum="3"
        android:visibility="gone">

        <ImageView
            android:id="@+id/imgProfilePic"
            android:layout_width="80dp"
            android:layout_height="wrap_content" 
            android:layout_weight="1"/>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:orientation="vertical"
            android:layout_weight="2" >

            <TextView
                android:id="@+id/txtName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="5dp"
                android:textSize="20dp" />

            <TextView
                android:id="@+id/txtEmail"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="5dp"
                android:textSize="18dp" />
        </LinearLayout>
    </LinearLayout>

    <com.google.android.gms.common.SignInButton
        android:id="@+id/btn_sign_in"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:layout_marginBottom="20dp"/>

    <Button
        android:id="@+id/btn_sign_out"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/btn_logout_from_google"
        android:visibility="gone" 
        android:layout_marginBottom="10dp"/>

    <Button
        android:id="@+id/btn_revoke_access"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/btn_revoke_access"
        android:visibility="gone" />

</LinearLayout>

and this is how i navigate 
    startActivity(new Intent("com.foo.app.Login"));
    finish();

my error :

08-29 13:31:55.668: E/AndroidRuntime(9232): FATAL EXCEPTION: main
  08-29 13:31:55.668: E/AndroidRuntime(9232):
  java.lang.RuntimeException: Unable to instantiate activity
  ComponentInfo{com.foo.app/com.foo.app.LoginActivity}:
  java.lang.ClassNotFoundException: Didn't find class
  "com.foo.app.LoginActivity" on path: DexPathList[[zip file
  "/data/app/com.foo.app-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.foo.app-1,
  /vendor/lib, /system/lib]] 08-29 13:31:55.668: E/AndroidRuntime(9232):
    at
  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2264)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  android.app.ActivityThread.access$600(ActivityThread.java:144) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  android.app.ActivityThread$H.handleMessage(ActivityThread.java:1259)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  android.os.Handler.dispatchMessage(Handler.java:99) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  android.os.Looper.loop(Looper.java:137) 08-29 13:31:55.668:
  E/AndroidRuntime(9232):   at
  android.app.ActivityThread.main(ActivityThread.java:5152) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  java.lang.reflect.Method.invokeNative(Native Method) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  java.lang.reflect.Method.invoke(Method.java:525) 08-29 13:31:55.668:
  E/AndroidRuntime(9232):   at
  com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:744)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  dalvik.system.NativeStart.main(Native Method) 08-29 13:31:55.668:
  E/AndroidRuntime(9232): Caused by: java.lang.ClassNotFoundException:
  Didn't find class "com.foo.app.LoginActivity" on path:
  DexPathList[[zip file
  "/data/app/com.foo.app-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.foo.app-1,
  /vendor/lib, /system/lib]] 08-29 13:31:55.668: E/AndroidRuntime(9232):
    at
  dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:53)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  java.lang.ClassLoader.loadClass(ClassLoader.java:501) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  java.lang.ClassLoader.loadClass(ClassLoader.java:461) 08-29
  13:31:55.668: E/AndroidRuntime(9232):     at
  android.app.Instrumentation.newActivity(Instrumentation.java:1061)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   at
  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2131)
  08-29 13:31:55.668: E/AndroidRuntime(9232):   ... 11 more

A:

startActivity(new Intent(calleractivty.this, LoginActivity.class));

and in the manifest
 <activity android:name=".SplashActivity" ...

if you look and the stack 

Unable to instantiate activity
  ComponentInfo{com.foo.app/com.foo.app.LoginActivity}:  it tries to reach wrong path

then it should work.

