2021-05-17 19:47:17
关于 Fragment 可以归纳出如下特征:
为了在 Activity 中显示 Fragment,还必须将 Fragment 添加到 Activity 中。将 Fragment 添加到 Activity 中有如下两种方式:
Fragment 与 Activity 之间传递数据
FragmentManager 可以完成如下的功能:
如果我们需要添加、删除、替换 Fragment,则需要使用 FragmentTransaction 对象,它 代表 Activity 对 Fragment 执行多个改变。我们可以通过如下方法获取 FragmentTransaction 对象:
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
在调用 commit() 方法之前,我们也可以调用 addToBackStack() 方法将事务添加到 back 栈中,该栈由 Activity 负责管理,这样允许用户按下 BACK 键返回到上一个 Fragment 的状态。
示例代码:
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.book_detail_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
首先是 fragment_book_detail.xml 布局文件:
<?xml version="1.0" encoding="utf-8"?>
接下来是 activity_book_twopane.xml 布局文件:
<?xml version="1.0" encoding="utf-8"?>
接下来,是 BookContent.java 文件:
package com.toby.personal.testlistview;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Created by toby on 17-3-29.
*/
class BookContent {
static class Book {
public Integer id;
String title;
String desc;
Book(Integer id, String title, String desc) {
this.id = id;
this.title = title;
this.desc = desc;
}
@Override
public String toString() {
return title;
}
}
static List ITEMS = new ArrayList<>();
static Map ITEM_MAP = new HashMap<>();
static {
addItem(new Book(1, "小狗钱钱", "理财入门读物"));
addItem(new Book(2, "小狗钱钱的爸爸", "理财入门读物"));
addItem(new Book(3, "穷爸爸和富爸爸", "理财入门读物"));
}
private static void addItem(Book book) {
ITEMS.add(book);
ITEM_MAP.put(book.id, book);
}
}
接下来,是 BookListFragment.java 文件:
package com.toby.personal.testlistview;
import android.app.ListFragment;
import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
/**
* Created by toby on 17-3-29.
*/
public class BookListFragment extends ListFragment {
private Callbacks callbacks;
interface Callbacks {
void onItemSelected(Integer id);
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setListAdapter(new ArrayAdapter<>(getActivity(),
android.R.layout.simple_list_item_activated_1,
android.R.id.text1, BookContent.ITEMS));
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (!(context instanceof Callbacks)){
throw new IllegalStateException("Callbacks interface must be implemented!");
}
callbacks = (Callbacks) context;
}
@Override
public void onDetach() {
super.onDetach();
callbacks = null;
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
callbacks.onItemSelected(BookContent.ITEMS.get(position).id);
}
public void setActivateOnItemClick(boolean activateOnItemClick) {
getListView().setChoiceMode(activateOnItemClick ?
ListView.CHOICE_MODE_SINGLE: ListView.CHOICE_MODE_NONE);
}
}
接下来,是 BookDetailFragment.java 文件:
package com.toby.personal.testlistview;
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
/**
* Created by toby on 17-3-29.
*/
public class BookDetailFragment extends Fragment {
final public static String ITEM_ID = "item_id";
private BookContent.Book book;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments().containsKey(ITEM_ID)) {
book = BookContent.ITEM_MAP.get(getArguments().getInt(ITEM_ID));
}
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_book_detail, container, false);
if (book != null) {
((TextView) rootView.findViewById(R.id.book_title)).setText(book.title);
((TextView) rootView.findViewById(R.id.book_desc)).setText(book.desc);
}
return rootView;
}
}
接下来,是 SelectBookActivity.java 文件:
package com.toby.personal.testlistview;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.annotation.Nullable;
/**
* Created by toby on 17-3-29.
*/
public class SelectBookActivity extends Activity implements BookListFragment.Callbacks {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_book_twopane);
}
@Override
public void onItemSelected(Integer id) {
Bundle arguments = new Bundle();
arguments.putInt(BookDetailFragment.ITEM_ID, id);
BookDetailFragment fragment = new BookDetailFragment();
fragment.setArguments(arguments);
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.book_detail_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
}
最后,调整 AndroidManifest.xml 文件:
程序在虚拟机上的运行效果:
参考文献:《疯狂Android讲义(第2版)》
原文链接:http://www.yuepc.com/a/71946.html
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