我的 android 中有 3 个滑动选项卡(A、B、C)。当涉及到选项卡 c 时，我有一个函数 RetrieveData()，用于从 MySQL 检索数据并加载到 listView。

假设在MySQL中我只有一行数据，当涉及到c时，数据将被加载到listView中(只有一个列表)。当我滑动到选项卡 A 并再次滑动到 C 时，列表现在变为 2。 有没有办法让 RetrieveData() 只调用一次？谢谢。

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View edit_details = inflater.inflate(R.layout.edit_work_details, container, false);
       // EditDetails = new ArrayList<HashMap<String, String>>();
        listViewUpdate = (ListView) edit_details.findViewById(R.id.listViewEdit);
        totalHours=(TextView)edit_details.findViewById(R.id.hour);
        setHasOptionsMenu(true);
        Bundle bundle = this.getArguments();
        if (getArguments() != null) {
            ID = bundle.getString("ID");
           RetrieveData(ID); // retrieve data from MySQL
        }
        Toast.makeText(getActivity(), "Details" + ID, Toast.LENGTH_LONG).show();
      }

TabAdapter

public class TabsFragmentPagerAdapter extends FragmentPagerAdapter {

    public TabsFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
        // TODO Auto-generated constructor stub
    }

    @Override
    public Fragment getItem(int index) {
        // TODO Auto-generated method stub

        if(index == 0) {

            Fragment fragment=new A();
            Bundle bundle = new Bundle();
            bundle.putString("ID", Edit.ID);
            fragment.setArguments(bundle);
            return fragment;

        }
        if(index == 1) {
            Fragment fragment = new B();
            Bundle bundle = new Bundle();
            bundle.putString("ID", Edit.ID);
            fragment.setArguments(bundle);
            return fragment;
        }

        if(index == 2) {
            Fragment fragment = new C();
            Bundle bundle = new Bundle();
            bundle.putString("ID", Edit.ID);
            fragment.setArguments(bundle);
            return fragment;
        }

        return null;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return 3;
    }

}

ViewPager代码

public class ActivityB extends ActionBarActivity implements ActionBar.TabListener {

    private ViewPager viewPager;
    private ActionBar actionBar;
    private TabsFragmentPagerAdapter tabsAdapter;
    private String[] item = new String[]{"Information","Work Force","Work Details"};
    private String id;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_b);
//        id=getIntent().getExtras().getString("ID");
        viewPager = (ViewPager) findViewById(R.id.viewPager);
        tabsAdapter = new TabsFragmentPagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(tabsAdapter);
        actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        for(int i=0; i<4; i++){
            actionBar.addTab(actionBar.newTab().setText(item[i]).setTabListener(this));
        }
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int arg) {
                // TODO Auto-generated method stub
                actionBar.setSelectedNavigationItem(arg);
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onPageScrollStateChanged(int arg0) {
                // TODO Auto-generated method stub

            }
        });

    }



    @Override
    public void onTabReselected(ActionBar.Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction arg1) {
        // TODO Auto-generated method stub
        viewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

}

这是我的标签c

再次滑动到A和C之后

似乎它再次调用了 RetrieveData。

最佳答案

您应该使用 ViewPager 的 setOffscreenPageLimit。它将设置您首先要加载多少页寻呼机。

setOffScreeenPageLimit 的默认值为 1，因此它将加载当前页面和下一页。在您的情况下，它将加载 A 和 B，当您从 B 移动到 C 时，它将销毁实例的 A。

尝试使用

`pager.setOffscreenPageLimit(2)`

它将加载当前页面和另外 2 个页面，因此 A、B 和 C 将加载一次。

编辑

Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state. Pages beyond this limit will be recreated from the adapter when needed.

This is offered as an optimization. If you know in advance the number of pages you will need to support or have lazy-loading mechanisms in place on your pages, tweaking this setting can have benefits in perceived smoothness of paging animations and interaction. If you have a small number of pages (3-4) that you can keep active all at once, less time will be spent in layout for newly created view subtrees as the user pages back and forth.

Source

这显然意味着您可以设置初始级别要加载的页面数，如果您想在第一次运行时加载 5 个页面，请将其值设置为 4。

现在，如果您要从 5 个页面中的任何一个页面移动，Fragment 的 onCreateView() 将不会被调用，因为它已经在初始阶段加载。

关于android - 停止选项卡中的函数调用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34804096/