android - 安装 PreferenceFragmentCompat 的支持库

Question

我是 Android Studio 的新手，总体上是 Android 编程的初学者。我看了又看，找不到合适的事情做。

我只想安装一个库来使用 PreferenceFragmentCompat 或任何替换 android.app.PreferenceFragment 的类，这样我的应用程序就可以在 API 11 及更低版本中运行。

谁能给我一些详细信息，例如我应该使用哪个库以及如何在我的 AS 项目中安装它。

编辑: 所以我开始使用 android.support.v4 和 android.support.v7 库来处理 fragment ，所以我开始开发这个应用程序我可以在 API 11 及更低版本上运行它。

这是我的 MainActivity.java。

package com.example.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.ActionBar;

import android.content.Context;
import android.os.Build;
import android.os.Bundle;
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.support.v4.widget.DrawerLayout;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

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

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {
        Fragment mainFragment = null;

        switch(position) {
            case 0: // home fragment
                mainFragment = new HomeFragment();
                break;
            case 1: // favorites list
                mainFragment = new FaveFragment();
                break;
            case 2: // rate app
                /* visit app TODO put application package id in the link */
                Intent visitStore = new Intent(Intent.ACTION_VIEW);
                visitStore.setData(Uri.parse("market://details?id=com.google.android.apps.maps"));
                startActivity(visitStore);
                break;
            case 3: // settings
                mainFragment = new SettingsFragment();
                break;
            case 4: // about
                mainFragment = new AboutFragment();
                break;

        }

        if(position != 2) {
            // update the main content by replacing fragments
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.container, mainFragment)
                    .commit();
        }
    }

    public void onSectionAttached(int number) {
        String[] stringArray = getResources().getStringArray(R.array.section_titles);
        if (number >= 1) {
            mTitle = stringArray[number - 1];
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.main, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @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 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);
            return rootView;
        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            ((MainActivity) activity).onSectionAttached(
                    getArguments().getInt(ARG_SECTION_NUMBER));
        }
    }

}

现在这是我的 SettingsFragment.java:

package com.example.myapplication;

import android.os.Bundle;
import android.preference.PreferenceFragment;

public class SettingsFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        addPreferencesFromResource(R.xml.settings);
    }
}

我在这里遇到的真正问题是这一行: MainActivity.java 中的 onNavigationDrawerItemSelected(int position) 方法中的 mainFragment = new SettingsFragment(); 。

它返回一个错误说:

Error:(70, 32) error: incompatible types: SettingsFragment cannot be converted to Fragment

如何解决这个问题，并且仍然能够在 API 11 及更低版本上使用我的应用？

Answer 1

将 com.android.support:preference-v7:23.0.1 添加到您的 build.gradle 文件后，只需更改行

对于 AndroidX:androidx.preference:preference:1.0.0

public class SettingsFragment extends PreferenceFragment {

到

public class SettingsFragment extends PreferenceFragmentCompat {

错误是由 PreferenceFragment 引起的，它扩展了 android.app.Fragment，而不是 android.support.v4.app.Fragment您需要，因为您正在使用支持库类。