FragmentStatePagerAdapter

FragmentStatePagerAdapter

我知道关于该主题还有其他几篇文章,但是我想粘贴我的代码,因为我认为其中可能有错误导致我的问题。我的FragmentStatePagerAdapter返回错误的位置,我不确定为什么。

这是我的主要活动中的代码。

Main.java

 import android.content.Context;
    import android.content.Intent;
    import android.graphics.Typeface;
    import android.os.Bundle;
    import android.support.design.widget.TabLayout;
    import android.support.v4.app.Fragment;
    import android.support.v4.app.FragmentTabHost;
    import android.support.v4.content.ContextCompat;
    import android.support.v4.view.ViewPager;
    import android.support.v7.app.ActionBar;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
    import android.view.LayoutInflater;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Button;
    import android.widget.ImageButton;
    import android.widget.ImageView;
    import android.widget.TabHost.OnTabChangeListener;
    import android.widget.TextView;
    import android.widget.Toast;

    import com.google.android.gms.common.ConnectionResult;
    import com.google.android.gms.common.GoogleApiAvailability;
    import com.google.android.gms.gcm.GoogleCloudMessaging;
    import com.microsoft.windowsazure.notifications.NotificationsManager;

    import java.util.ArrayList;

    public class Main extends AppCompatActivity {

        public static TextView txtViewHeading;
        public static TextView tab1TabBadge;
        public static TextView tab2TabBadge;
        public static TextView tab3TabBadge;
        public static TextView tab4TabBadge;
        public static TextView tab5TabBadge;
        public static Button btnBack;
        public static ImageButton btnShare;
        public static Main mainActivity;
        public static Context mainActivityContext;
        public static Boolean isVisible = false;
        private FragmentTabHost mTabHost;
        private GoogleCloudMessaging gcm;
        private ActionBar actionBar;
        private static final int PLAY_SERVICES_RESOLUTION_REQUEST = 9000;

        private TabGroupAdapter mTabGroupAdapter;
        private ViewPager mViewPager;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            // Set up Push notifications
            mainActivity = this;
            mainActivityContext = Main.this;
            NotificationsManager.handleNotifications(this, NotificationSettings.SenderId, PushHandler.class);
            registerWithNotificationHubs();

            // Set up the views for each tab - custom view used for Badge icon
            LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            // Bind the Toolbar
            Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);

            // Set up the ActionBar
            actionBar = getSupportActionBar();
            if (actionBar!=null) {
                actionBar.setDisplayHomeAsUpEnabled(true);
                actionBar.setHomeButtonEnabled(true);
            }

            // Create the adapter that will return a fragment for each of the primary "tabs"
            mTabGroupAdapter = new TabGroupAdapter(getSupportFragmentManager());

            // Set up the ViewPager with the sections adapter.
            mViewPager = (ViewPager) findViewById(R.id.container);
            mViewPager.setAdapter(mTabGroupAdapter);

            TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
            tabLayout.setupWithViewPager(mViewPager);

            // tab1 Tab
            View tab1TabView = inflater.inflate(R.layout.tab, null);
            ImageView tab1TabIcon = (ImageView) tab1TabView.findViewById(R.id.tabIcon);
            tab1TabIcon.setImageResource(R.drawable.tab_first);
            TextView tab1TabText = (TextView) tab1TabView.findViewById(R.id.tabText);
            tab1TabText.setText("tab1");
            tab1TabText.setTypeface(arialTypeface);
            tab1TabBadge = (TextView) tab1TabView.findViewById(R.id.tabBadge);
            tab1TabBadge.setTypeface(arialTypeface);
            tabLayout.getTabAt(0).setCustomView(tab1TabView);
            // Also set this tab as Active be default
            tabLayout.getTabAt(0).getCustomView().setSelected(true);
            mViewPager.setCurrentItem(0);

            // tab2 Tab
            View tab2TabView = inflater.inflate(R.layout.tab, null);
            ImageView tab2TabIcon = (ImageView) tab2TabView.findViewById(R.id.tabIcon);
            tab2TabIcon.setImageResource(R.drawable.tab_second);
            TextView tab2TabText = (TextView) tab2TabView.findViewById(R.id.tabText);
            tab2TabText.setText("Odometer");
            tab2TabText.setTypeface(arialTypeface);
            tab2TabBadge = (TextView) tab2TabView.findViewById(R.id.tabBadge);
            tab2TabBadge.setTypeface(arialTypeface);
            tabLayout.getTabAt(1).setCustomView(tab2TabView);

            // tab3 Tab
            View tab3TabView = inflater.inflate(R.layout.tab, null);
            ImageView tab3TabIcon = (ImageView) tab3TabView.findViewById(R.id.tabIcon);
            tab3TabIcon.setImageResource(R.drawable.tab_third);
            TextView tab3TabText = (TextView) tab3TabView.findViewById(R.id.tabText);
            tab3TabText.setText("tab3");
            tab3TabText.setTypeface(arialTypeface);
            tab3TabBadge = (TextView) tab3TabView.findViewById(R.id.tabBadge);
            tab3TabBadge.setTypeface(arialTypeface);
            tabLayout.getTabAt(2).setCustomView(tab3TabView);

            // tab4 Tab
            View tab4TabView = inflater.inflate(R.layout.tab, null);
            ImageView tab4TabIcon = (ImageView) tab4TabView.findViewById(R.id.tabIcon);
            tab4TabIcon.setImageResource(R.drawable.tab_fourth);
            TextView tab4TabText = (TextView) tab4TabView.findViewById(R.id.tabText);
            tab4TabText.setText("tab4");
            tab4TabText.setTypeface(arialTypeface);
            tab4TabBadge = (TextView) tab4TabView.findViewById(R.id.tabBadge);
            tab4TabBadge.setTypeface(arialTypeface);
            tabLayout.getTabAt(3).setCustomView(tab4TabView);

            // tab5 Tab
            View tab5TabView = inflater.inflate(R.layout.tab, null);
            ImageView tab5TabIcon = (ImageView) tab5TabView.findViewById(R.id.tabIcon);
            tab5TabIcon.setImageResource(R.drawable.tab_fifth);
            TextView tab5TabText = (TextView) tab5TabView.findViewById(R.id.tabText);
            tab5TabText.setText("tab5");
            tab5TabText.setTypeface(arialTypeface);
            tab5TabBadge = (TextView) tab5TabView.findViewById(R.id.tabBadge);
            tab5TabBadge.setTypeface(arialTypeface);
            tabLayout.getTabAt(4).setCustomView(tab5TabView);

            // Tab listener
            /*
            tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
                @Override
                public void onTabSelected(TabLayout.Tab tab) {
                    txtViewHeading.setText(tab.getText());
                }

                @Override
                public void onTabUnselected(TabLayout.Tab tab) {

                }

                @Override
                public void onTabReselected(TabLayout.Tab tab) {

                }
            });
            */

        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            int id = item.getItemId();
            if (id == android.R.id.home) {
                if(mViewPager.getCurrentItem()==0){
                    onBackPressed();
                }
                else{
                    mViewPager.setCurrentItem(mViewPager.getCurrentItem()-1);
                }
            }
            return super.onOptionsItemSelected(item);
        }

        @Override
        protected void onPause() {
            super.onPause();
            isVisible = false;
        }

        @Override
        protected void onResume() {
            super.onResume();
            isVisible = true;
        }

        @Override
        protected void onStop() {
            super.onStop();
            isVisible = false;
        }

        private boolean checkPlayServices() {
            GoogleApiAvailability apiAvailability = GoogleApiAvailability.getInstance();
            int resultCode = apiAvailability.isGooglePlayServicesAvailable(this);
            if (resultCode != ConnectionResult.SUCCESS) {
                if (apiAvailability.isUserResolvableError(resultCode)) {
                    apiAvailability.getErrorDialog(this, resultCode, PLAY_SERVICES_RESOLUTION_REQUEST)
                            .show();
                } else {
                    ToastNotify("This device is not supported by Google Play Services.");
                    finish();
                }
                return false;
            }
            return true;
        }

        public void ToastNotify(final String notificationMessage) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(Main.this, notificationMessage, Toast.LENGTH_LONG).show();
                }
            });
        }

        private void registerWithNotificationHubs()
        {
            if (checkPlayServices()) {
                // Start IntentService to register this application with GCM.
                Intent intent = new Intent(this, RegistrationIntentService.class);
                startService(intent);
            }
        }

    }


...这是我的FragmentStatePagerAdapter的代码

TabGroupAdapter

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.util.Log;

import java.util.ArrayList;


public class TabGroupAdapter extends FragmentStatePagerAdapter {

    private static int fragmentSize = 5;
    private static ArrayList<String> fragmentTitles = new ArrayList<String>() {
        {
            add("tab1");
            add("tab2");
            add("tab3");
            add("tab4");
            add("tab5");
        }
    };

    public TabGroupAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        Log.d("tag","POSITION: " + position);
        switch (position) {
            case 0:
            default:
                return new Tab1Fragment();
            case 1:
                return new Tab2Fragment();
            case 2:
                return new Tab3Fragment();
            case 3:
                return new Tab4Fragment();
            case 4:
                return new Tab5Fragment();
        }
    }

    @Override
    public int getCount() {
        return fragmentSize;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return fragmentTitles.get(position);
    }


}


综上所述,当我的应用加载时,第一个标签为空。只是一个空白的屏幕。它不是我应该的Tab1Fragment。同样,当我单击选项卡时,位置应该从左到右显示0、1、2、3、4,因为我有5个选项卡。虽然没有。我的getItem(position)方法中有一个Log.d语句,其中将当前位置记录到控制台中。当我的应用加载时,显示位置0,然后显示位置1:全部处于加载状态,这很奇怪,因为它应该仅显示位置0,因为这是默认标签(tab1)。然后,当我单击时,选项卡2显示位置2,选项卡3显示位置3,选项卡4显示位置4,而选项卡5根本不记录。然后从选项卡5移回到选项卡1,这些位置全都不用了,当我进入选项卡1时,它不会登录。真奇怪另外,片段中的后退箭头应该仅在我不在选项卡的根片段时才显示,而是一直显示。

谁能帮我弄清楚为什么会这样吗?
如果需要更多代码来确定问题,我很乐意将其发布,请告诉我您需要看什么。

最佳答案

尝试注释掉下面的所有代码:

 TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);


在您的onCreate方法中。再次运行,看看会发生什么。

您的switch语句的布局也很奇怪。如果绝对只有5种情况,则应从0-4情况开始,最后是默认情况,该情况会在日志中输出错误或引发异常。我认为这不会引起您的问题,但这是一个好习惯。

同样,使用默认构造函数实例化片段通常也不是一个好主意。更好的方法是使用静态工厂方法,即:

Tab1Fragment fragment = Tab1Fragment.create();
return fragment;


在片段中使用静态create()方法可以初始化对象。它为您提供了一个单一的片段访问点,这意味着您需要进行的任何初始化(现在或在该行的某个点)都可以一次完成,从而减少了出错的可能性。 Android还使用默认构造函数重新创建片段,因此您将在重载的构造函数中进行的任何初始化都会被忽略。同样,我不认为这是造成您问题的原因,但值得牢记。

编辑:此外,当您说正在选择随机片段“位置将仅显示随机数0、3、2、0、4、1”时,您是说这些是正在屏幕上显示的片段,还是那些您从“ getItem(int position)”参数记录的位置?

07-24 09:48
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