Java 无法恢复Android应用程序中的活动错误
因此,我有一个零碎的活动,它目前运行得很好Java 无法恢复Android应用程序中的活动错误,java,android,android-fragments,Java,Android,Android Fragments,因此,我有一个零碎的活动,它目前运行得很好 public class ChallongeEvent extends FragmentActivity { private TextView tab_text; private String EVENT_ID, URL; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstance
public class ChallongeEvent extends FragmentActivity {
private TextView tab_text;
private String EVENT_ID, URL;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.challonge_act_event);
init();
}
private void init() {
tab_text = (TextView) findViewById(R.id.tab_text);
Intent intent = getIntent();
EVENT_ID = intent.getStringExtra("event_id");
URL = "https://api.challonge.com/v1/tournaments/" + EVENT_ID + ".json";
String titles[] = new String[] { getString(R.string.details), getString(R.string.players) };
int numTabs = titles.length;
EventAdapter adapter = new EventAdapter(getSupportFragmentManager(), titles, numTabs);
ViewPager pager = (ViewPager) findViewById(R.id.pager);
pager.setAdapter(adapter);
pager.setCurrentItem(numTabs - 1);
SlidingTabLayout sliding_tabs = (SlidingTabLayout) findViewById(R.id.sliding_tabs);
sliding_tabs.setDistributeEvenly(true);
sliding_tabs.setViewPager(pager);
}
@Override
public void onResume() {
super.onResume();
populate();
}
private void populate() {
AsyncGet fetch = new AsyncGet(new AsyncResponse() {
@Override
public void processFinish(String output) {
for (Fragment fragment : getSupportFragmentManager().getFragments())
{
if (fragment instanceof ChallongePlayers) {
((ChallongePlayers) fragment).parsePlayers(output);
} else if (fragment instanceof ChallongeMatches) {
((ChallongeMatches) fragment).parseMatches(output);
}
}
}
});
HttpUrl.Builder urlBuilder = HttpUrl.parse(URL).newBuilder();
urlBuilder.addQueryParameter("api_key", Challonge.API_KEY);
urlBuilder.addQueryParameter("include_participants", "1");
urlBuilder.addQueryParameter("include_matches", "1");
fetch.execute(urlBuilder.build().toString());
}
}
当FragmentActivity启动时,它从API获取JSON,然后将此API的数据发送到寻呼机中的多个片段。它使用以下代码执行此操作:
AsyncGet fetch = new AsyncGet(new AsyncResponse() {
@Override
public void processFinish(String output) {
for (Fragment fragment : getSupportFragmentManager().getFragments())
{
if (fragment instanceof ChallongePlayers) {
((ChallongePlayers) fragment).parsePlayers(output);
} else if (fragment instanceof ChallongeMatches) {
((ChallongeMatches) fragment).parseMatches(output);
}
}
}
});
HttpUrl.Builder urlBuilder = HttpUrl.parse(URL).newBuilder();
urlBuilder.addQueryParameter("api_key", Challonge.API_KEY);
urlBuilder.addQueryParameter("include_participants", "1");
urlBuilder.addQueryParameter("include_matches", "1");
fetch.execute(urlBuilder.build().toString());
但是,这些片段中的每一个都有一个SwipeRefreshLayout
,我想在AsyncTask请求之前激活它。因此,我将每个片段上的SwipeRefreshLayout设置为公共,并尝试在AsyncGet fetch=…
行上方添加以下内容:
for (Fragment fragment : getSupportFragmentManager().getFragments())
{
if (fragment instanceof ChallongePlayers) {
((ChallongePlayers) fragment).swipe_container.setRefreshing(true);
} else if (fragment instanceof ChallongeMatches) {
((ChallongeMatches) fragment).swipe_container.setRefreshing(true);
}
}
不幸的是,此代码的第一行产生错误:
java.lang.NullPointerException:尝试对空对象引用调用接口方法“java.util.Iterator java.util.List.Iterator()”
为什么不起作用?调用
getFragments()
返回的集合尚未初始化,为空
如果检查以确保getFragments()
在迭代之前不会返回null
集合,则可以添加:
if(getSupportFragmentManager().getFragments() != null) {
for (Fragment fragment : getSupportFragmentManager().getFragments())
{
if (fragment instanceof ChallongePlayers) {
((ChallongePlayers) fragment).swipe_container.setRefreshing(true);
} else if (fragment instanceof ChallongeMatches) {
((ChallongeMatches) fragment).swipe_container.setRefreshing(true);
}
}
}
是否可能在调用getSupportFragmentManager().getFragments()
时您还没有添加任何片段?这些片段是在init()
中添加的,这发生在onCreate
之后,第一次运行填充可以发生在onResume
中。getSupportFragmentManager().executePendingTransactions()代码>未更改任何内容。。。但是检查空值是一个足够好的解决方案。那么最好将其从答案中删除。我想,FragmentPagerAdapter
一定在对片段做一些不同的处理。