问How to run Splash screen然后intro & main activity

EN

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name="info.androidhive.introslider.Splashscreen">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="info.androidhive.introslider.WelcomeActivity" />
        <activity
            android:name="info.androidhive.introslider.MainActivity"
            android:label="@string/title_activity_welcome"
            android:theme="@style/AppTheme.NoActionBar"/>
    </application>  
</manifest>

package info.androidhive.introslider;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
public class Splashscreen extends Activity {
    private static int SPLASH_TIMER = 1000;
    @Override
    protected void onCreate( Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);
            new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                Intent i = new Intent(Splashscreen.this,MainActivity.class);
                startActivity(i);
                finish();
            }
        },SPLASH_TIMER);
    }
}