java - 切换 fragment 时滑动选项卡滞后

Question

我有一个小问题，我只有 3 个 fragment ，我向其中一个 fragment 添加了 Photoshop 背景(1080 x 1920)，问题是当它加载到手机时，选项卡之间的切换会滞后很多，但是如果我只是将图像渲染到 720 x 1280 它工作正常并且没有出现延迟，我实现了 mViewPager.setOffscreenPageLimit(0); 但它似乎不起作用，我不知道是什么导致了问题，我将在这里放置我的主要代码，提前致谢

import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;

import android.widget.ExpandableListView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setOffscreenPageLimit(0);
        mViewPager.setAdapter(mSectionsPagerAdapter);

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

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }




    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */


    //-----------------------FRAGMENTS-----------------------

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).


            switch (position) {
                case 0:
                    Fragment fragment = new DummySectionFragment3();
                    Bundle args = new Bundle();
                    args.putInt(DummySectionFragment3.ARG_SECTION_NUMBER, position + 1);
                    fragment.setArguments(args);
                    return fragment;

                case 1:
                    Fragment fragment2 = new DummySectionFragment2();
                    Bundle args2 = new Bundle();
                    args2.putInt(DummySectionFragment2.ARG_SECTION_NUMBER, position + 2);
                    fragment2.setArguments(args2);
                    return fragment2;

                case 2:

                    Fragment fragment3 = new DummySectionFragment();
                    Bundle args3 = new Bundle();
                    args3.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 3);
                    fragment3.setArguments(args3);
                    return fragment3;


                default:
                    return null;
            }
        }
        //-----------------------FRAGMENTS-----------------------



        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }



        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "Bares";
                case 1:
                    return "No se";
                case 2:
                    return "Eventos";
            }
            return null;
        }
    }





    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        public PlaceholderFragment() {
        }




        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
            dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }
    }

Answer 1

i implemented mViewPager.setOffscreenPageLimit(0); but it seems it dosnt work

首先，

如果您希望滑动更顺畅，为什么要将页面限制设置为 0？

这样做(如果您有 3 个选项卡，只需将 limitiit 设置为 1 ，如果有 5 个选项卡，则将其设置为 2 即可)

mViewPager.setOffscreenPageLimit(2); 

这意味着您正在强制缓存当前选项卡中的 2 个左侧选项卡和 2 个右侧选项卡。

这样它们就不会被一次又一次加载，而是会被缓存。

注意话虽如此，您应该记住它会消耗更多内存并避免不必要的内存消耗。

希望它对某人有帮助。