小编use*_*350的帖子

我正在尝试在Android中编写代码,以在向下滚动事件期间隐藏Actionbar.我有一个10x50的网格.因此,当我向下滚动时,操作栏应该隐藏.我正确地在Log Cat中获得滚动状态结果,所以每当我申请getActionBar()时,我都会收到NullPointerException错误.

我的代码:

package com.example.complexdatepicker;

import android.app.TabActivity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;

public class MainActivity extends TabActivity 
{

@Override
protected void onCreate(Bundle savedInstanceState) 
{


        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        TabHost tabHost = getTabHost();


        TabSpec tab1 = tabHost.newTabSpec("Home");

        tab1.setIndicator("Home");
        Intent photosIntent = new Intent(this, Home.class);
        tab1.setContent(photosIntent);

        tabHost.addTab(tab1);


}

 }

Home.java

package com.example.complexdatepicker;

import java.util.ArrayList;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.GridView;


public class Home extends ActionBarActivity 
{

ArrayList<String> abc;

TestGrid tg;

GridView gv;

int mLastFirstVisibleItem;

int mLastVisibleItemCount;

@Override
protected void onCreate(Bundle savedInstanceState) …