为PreferenceFragmentCompat安装支持库

Question

我是Android Studio的新手，总的来说是Android编程的初学者。我看着，看着，我找不到合适的事情去做。

所有我想要的是安装库使用PreferenceFragmentCompat或替换android.app.PreferenceFragment任何类，所以我的应用程序可以在11 API和较低的工作。

任何人都可以请给我一些细节，如我应该使用哪个库以及如何将它安装在我的AS项目中。

编辑：于是我开始开发使用android.support.v4和android.support.v7库来处理的片段，所以我可以在11 API和更低的运行这个程序。

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); 
    } 
} 

我在这里遇到真正的问题是这一行：mainFragment = new SettingsFragment();在onNavigationDrawerItemSelected(int position)方法MainActivity.java。

它返回一个错误说：

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

我怎样才能解决这个问题，仍然可以使用我的应用程序的API 11和低？

Answer 1

加入com.android.support:preference-v7:23.0.1到您的build.gradle文件后，只需将线

public class SettingsFragment extends PreferenceFragment { 

到

public class SettingsFragment extends PreferenceFragmentCompat { 

错误是由PreferenceFragment引起的，它扩展android.app.Fragment，不android.support.v4.app.Fragment您需要，因为你正在使用支持库类。