我试图在ListFragment中实现动态更新列表。 但是，当我更改我的片段（即从片段1到片段2并返回到片段1）时，列表内容将丢失。
下面是我的ListFragment。
public class FragmentOne extends ListFragment {
String[] order = new String[] {};
public FragmentOne(){}
/** Items entered by the user is stored in this ArrayList variable */
ArrayList<String> list = new ArrayList<String>();
/** Declaring an ArrayAdapter to set items to ListView */
ArrayAdapter<String> adapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.fragment_1, container, false);
/** Reference to the button of the layout main.xml */
Button btn = (Button) rootView.findViewById(R.id.btnAdd);
/** Defining a click event listener for the button "Add" */
OnClickListener listener = new OnClickListener() {
@Override
public void onClick(View v) {
EditText edit = (EditText) rootView.findViewById(R.id.txtItem);
list.add(edit.getText().toString());
edit.setText("");
adapter.notifyDataSetChanged();
}
};
/** Setting the event listener for the add button */
btn.setOnClickListener(listener);
/** Defining the ArrayAdapter to set items to ListView */
adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, list);
/** Setting the adapter to the ListView */
setListAdapter(adapter);
return rootView;
}}
编辑：
我试图实现一个滑块菜单，这是我的活动（对不起代码太长了）：
public class MainActivity extends FragmentActivity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
private CharSequence mDrawerTitle;
// used to store app title
private CharSequence mTitle;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.nav_drawer_icons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_slidermenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1), true, "4"));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1), true, "2"));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1), true, "4"));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "6"));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1), true, "8"));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "4"));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
//getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, //nav menu toggle icon
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
* */
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* *
* Called when invalidateOptionsMenu() is triggered
*/
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if nav drawer is opened, hide the action items
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
/**
* Diplaying fragment view for selected nav drawer list item
* */
private void displayView(int position) {
// update the main content by replacing fragments
ListFragment fragment = null;
switch (position) {
case 0:
fragment = new FragmentOne();
break;
case 1:
fragment = new FragmentTwo();
break;
case 2:
fragment = new FragmentThree();
break;
case 3:
fragment = new FragmentFour();
break;
case 4:
fragment = new FragmentFive();
break;
case 5:
fragment = new FragmentSix();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
}
提前致谢
答案 0 :(得分：0)
当您从Fragment2返回Fragment1时，您正在创建Fragment1的新实例。所以你的ListView当然是空的（直到用户通过你提供的按钮添加项目）。
也许您需要修改displayView(int position)所以它不会每次都通过空检查和全局变量来创建实例？
答案 1 :(得分：0)
正如@lenix在回到fragment1时提到的那样，displayView会创建一个新的片段，因为你对FragmentManager说我创建了一个新的片段并替换它。 在这种情况下，您应该检查isFragment已添加？否则添加否则隐藏并显示片段..
FragmentTransaction transaction = fragmentManager.beginTransaction();
if(fragment1.isAdded){
transaction.show(fragment1)
}else{
transaction.add(fragment1)
}
不要忘记在你完成时提交......并且它只是看你如何做的方式......这个片段不起作用..
答案 2 :(得分：0)
每次加载片段时，ArrayList都将从空开始。您可以将当前列表项保存到共享首选项，并在每次加载片段时获取列表，或在活动中实现set / get回调。