判断用户是否是第一次打开该app

package com.example.fujilun_2;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;

public class LaunchActivity extends Activity{
    //要保存的文件名
    private final String SHARE_APP_TAG= "firstOpen";
    private Boolean first;
    private SharedPreferences setting;
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_launch);

        setting = getSharedPreferences(SHARE_APP_TAG, 0);
        first = setting.getBoolean("FIRST",true); 

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                if(first){
                    setting.edit().putBoolean("FIRST", false).commit();
                    Intent intent=new Intent(LaunchActivity.this,DemoActivity.class);
                    startActivity(intent);
                    finish();
                }else{
                    Intent intent=new Intent(LaunchActivity.this,LoginActivity.class);
                    startActivity(intent);
                    finish();
                }

            }
        }).start();

    }
}