我有两个碎片：FragmentA和FragmentB。 FragmentA有一个按钮，FragmentB有一个ListView，其适配器设计为使用自定义行。我想通过单击FragmentA中的按钮在FragmentB中的这个ListView中添加一行。我已经研究了谷歌关于片段之间的沟通的一些文件，我写了一些代码，但我没有成功。我试图将一个按钮和ListView放在一个片段中。单击按钮时，我成功使用了适配器的notifiyDataSetChanged()方法。 Hovewer，我不知道如何解决这个问题。
我的MainActiviy.java：
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener, FragmentA.ButtonClickListener{
private static final int NUM_PAGES = 2;
private ViewPager mPager;
private PagerAdapter mPagerAdapter;
private ActionBar actionBar;
private String[] tabs = { "A", "B"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
// ViewPager's PageChangeListener.
mPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
});
// Retrieve actionbar and set some properties.
actionBar = getSupportActionBar();
// actionBar.setHomeButtonEnabled(true);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowCustomEnabled(true);
actionBar.setDisplayShowTitleEnabled(true);
Fragment frag1 = new FragmentA();
Fragment frag2 = new FragmentB();
FragmentTransaction fragmentTransaction;
FragmentManager fragMgr = getSupportFragmentManager();
fragmentTransaction = fragMgr.beginTransaction();
fragmentTransaction.add(frag1, "frag1Tag");
fragmentTransaction.add(frag2, "frag2Tag");
fragmentTransaction.commit();
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name).setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private class ViewPagerAdapter extends FragmentStatePagerAdapter {
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position){
case 0:
return new FragmentA();
case 1:
return new FragmentB();
}
return null;
}
@Override
public int getCount() {
return NUM_PAGES;
}
}
@Override
public void onButtonClicked() { // IMPLEMENTATION OF INTERFACE METHOD
FragmentB fragmentB = (FragmentB)getSupportFragmentManager().findFragmentByTag("frag2Tag");
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if (fragmentB != null) {
fragmentB.updateList();
} else {
FragmentB newFragment = new FragmentB();
}
}
}
我的FragmentA.java：
public class FragmentA extends Fragment {
ButtonClickListener mCallback;
FragmentTransaction ft;
List<String> values = new ArrayList<String>();
// Container Activity must implement this interface.
// INTERFACE DEFINATION.
public interface ButtonClickListener {
public void onButtonClicked();
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception
try {
mCallback = (ButtonClickListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnHeadlineSelectedListener");
}
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
ViewGroup vG = (ViewGroup)inflater.inflate(R.layout.fragment1_layout, container,false);
Button btn = (Button)vG.findViewById(R.id.button1);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCallback.onButtonClicked();
}
});
return vG;
}
}
我的FragmentB.java：
public class FragmentB extends Fragment {
List<String> values = new ArrayList<String>();
List<String> valuesRefresh = new ArrayList<String>();
ListView list;
MyListAdapter adapter;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
values.add("asda");
values.add("kasd");
ViewGroup vG = (ViewGroup)inflater.inflate(R.layout.fragment2_layout, container,false);
list = (ListView)vG.findViewById(R.id.listView2);
adapter = new MyListAdapter(getActivity(),values);
list.setAdapter(adapter);
return vG;
}
public void updateList(){
adapter.notifyDataSetChanged();
}
public static class MyListAdapter extends ArrayAdapter<String>{
private final Context context;
private final List<String> values = new ArrayList<String>();
public MyListAdapter(Context context, List<String> values) {
super(context, R.layout.list_item, values);
this.context = context;
for (int i=0; i<values.size(); i++) {
this.values.add(values.get(i));
}
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return 0;
}
public long getCount(int position) {
// TODO Auto-generated method stub
return values.size();
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View list = inflater.inflate(R.layout.list_item,parent,false);
return list;
}
}
}
答案 0 :(得分：1)
您的问题是，您正在活动的onCreate中创建片段，再次在寻呼机适配器中创建片段，再次在onButtonClicked（FragmentB）中创建片段。你应该只创建一次。由于您在Activity中执行了所有这些操作，因此最简单的方法是在Activity字段中保留对片段的引用。但是，您需要确保处理重新创建活动的情况，因为在这种情况下，Android已经重新创建了您的片段，您不需要再次创建和添加它们。
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener, FragmentA.ButtonClickListener{
private static final int NUM_PAGES = 2;
private ViewPager mPager;
private PagerAdapter mPagerAdapter;
private ActionBar actionBar;
private String[] tabs = { "A", "B"};
private Fragment frag1;
private Fragment frag2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// First check if Android has already created the fragments
FragmentManager fragMgr = getSupportFragmentManager();
frag1 = fragMgr.findFragmentByTag("frag1Tag");
frag2 = fragMgr.findFragmentByTag("frag2Tag");
if (frag1 == null && frag2 == null) {
// Create and add fragments only if needed
frag1 = new FragmentA();
frag2 = new FragmentB();
FragmentTransaction fragmentTransaction = fragMgr.beginTransaction();
fragmentTransaction.add(frag1, "frag1Tag");
fragmentTransaction.add(frag2, "frag2Tag");
fragmentTransaction.commit();
}
mPager = (ViewPager) findViewById(R.id.pager);
...
}
...
private class ViewPagerAdapter extends FragmentStatePagerAdapter {
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position){
case 0:
return frag1;
case 1:
return frag2;
}
return null;
}
@Override
public int getCount() {
return NUM_PAGES;
}
}
@Override
public void onButtonClicked() { // IMPLEMENTATION OF INTERFACE METHOD
frag2.updateList();
}
}