Android - 使用 Android Studio 默认 ViewPager 设置在 Activity 和 Fragment 之间传递数据

Question

我正在研究在 Activity (ActionBarActivity) 和 Fragment 之间传递数据。目前，我正在使用 Android Studio 生成的代码进行测试（唯一添加的是显示片段编号的 TextView）。

我已经看到指向使用捆绑包的答案，但是在这种情况下它似乎不起作用，因为捆绑包是在片段本身而不是父 Activity 内创建的。在这种情况下，使用默认实现，您将如何传递数据。或者，在不偏离基地太远的情况下，还有什么替代方案？

MainActivity.java（包含 activity、适配器和演示片段）

package com.blah.fragmentswitchingtest;

import java.util.Locale;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.FragmentPagerAdapter;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity {

    /**
     * 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}.
     */
    SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    ViewPager mViewPager;
    public String stringToCarry = "String"; // How would I carry this string to into the Fragment

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


        // 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.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

    }


    @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.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        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).
            return PlaceholderFragment.newInstance(position + 1);
        }

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

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
                case 2:
                    return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        protected TextView mSectionLabel;
        /**
         * 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);

            mSectionLabel = (TextView)rootView.findViewById(R.id.section_label);


            Integer myValue = this.getArguments().getInt(ARG_SECTION_NUMBER);
            String blah = myValue.toString();

            mSectionLabel.setText(blah);

            return rootView;
        }
    }

}

Answer 1

嗨，一个简单的解决方案是在主 activity 中创建一个 public 静态 class 并从片段

访问其属性

另一个是实现回调

例如在主 activity 中你创建一个静态的 class 像这样：

public static class MyData{

String mName;
String mSurname;

public MyData(String mName, String mSurname) {
    this.mName = mName;
    this.mSurname = mSurname;
}


public String getmName() {
    return mName;
}


public String getmSurname() {
    return mSurname;
}

}

同样在 Main Activity 中我们有一个 public 静态数组保存数据项：

public static ArrayList<MyData>mData = new ArrayList<>();

在 OnCreate Main Activity 我们填充数据：

mData.add(new MyData("John","Doe"));
mData.add(new MyData("Peter","Pan"));

从片段中我们可以像这样访问数据：

ArrayList<MainActivity.MyData>list = MainActivity.mData;

for(MainActivity.MyData obj : list){
    Log.d("DATA", obj.getmName() + " " + obj.getmSurname());

}