[英]App crashes when passing data from activity to fragment
我試圖通過一個活動傳遞來自fragmentA的一些數據,以在fragmentB中開始一個動作。 它的工作方式是,用戶在listview(listFragment)中按下一個項目,將項目數據發送到另一個片段(可見且已在運行),以使用來自fragmentA的數據開始新的事件/操作。
片段A:
@Override
public void onListItemClick(ListView listView, View view, int position,
long longId) {
super.onListItemClick(listView, view, position, longId);
String trackId = SD_PATH + songs.get(position);
mCallbacks.onTrackSelected(trackId);
通過活動:
@Override
public void onTrackSelected(String trackId) {
// This starts onTrackSelected() method in fragmentB
topBarFragment topBarFragment = (topBarFragment)getSupportFragmentManager().findFragmentById(R.id.topBar_fragment);
topBarFragment.onTrackSelected();
Bundle bundle = new Bundle();
bundle.putString("trackId", trackId);
//set Fragmentclass Arguments
topBarFragment fragObject = new topBarFragment();
fragObject.setArguments(bundle);
}
檢索fragmentB中的數據(這是崩潰的地方):
public void onTrackSelected() {
// crashes on this line
String trackId = getArguments().getString("trackId");
Toast.makeText(getActivity().getApplicationContext(), trackId,Toast.LENGTH_SHORT).show();
}
我已經檢查過,並且數據可以從fragmentA
傳遞到activity
,但是在嘗試接收fragmentB
時它崩潰了。
該怎么辦?
(fragmentB的當前活動與fragmentA的不同。這與它有關系嗎?)
logcat的:
02-24 23:28:47.757: E/AndroidRuntime(14047): FATAL EXCEPTION: main
02-24 23:28:47.757: E/AndroidRuntime(14047): java.lang.NullPointerException
02-24 23:28:47.757: E/AndroidRuntime(14047): at com.harteg.fragmentstest.topBarFragment.onTrackSelected(topBarFragment.java:47)
02-24 23:28:47.757: E/AndroidRuntime(14047): at com.harteg.fragmentstest.ItemListActivity.onTrackSelected(ItemListActivity.java:83)
02-24 23:28:47.757: E/AndroidRuntime(14047): at com.harteg.fragmentstest.TracksFragment.onListItemClick(TracksFragment.java:136)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.support.v4.app.ListFragment$2.onItemClick(ListFragment.java:58)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.widget.AdapterView.performItemClick(AdapterView.java:298)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.widget.AbsListView$1.run(AbsListView.java:3423)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.os.Handler.handleCallback(Handler.java:725)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.os.Handler.dispatchMessage(Handler.java:92)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.os.Looper.loop(Looper.java:137)
02-24 23:28:47.757: E/AndroidRuntime(14047): at android.app.ActivityThread.main(ActivityThread.java:5039)
02-24 23:28:47.757: E/AndroidRuntime(14047): at java.lang.reflect.Method.invokeNative(Native Method)
02-24 23:28:47.757: E/AndroidRuntime(14047): at java.lang.reflect.Method.invoke(Method.java:511)
02-24 23:28:47.757: E/AndroidRuntime(14047): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-24 23:28:47.757: E/AndroidRuntime(14047): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-24 23:28:47.757: E/AndroidRuntime(14047): at dalvik.system.NativeStart.main(Native Method)
更新:
我這樣更新代碼,發現getArguments()返回null。為什么?
Bundle arguments = getArguments();
if (arguments != null)
{
String trackId = getArguments().getString("trackId");
Toast.makeText(getActivity().getApplicationContext(), trackId,Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getActivity().getApplicationContext(), "arguments returns null", Toast.LENGTH_SHORT).show();
}
UPDATE
我在這樣的活動中更新了onTrackSelected(),但現在它崩潰了,並說該片段已處於活動狀態。 您如何解決這個問題?
@Override
public void onTrackSelected(String trackId) {
// TODO Auto-generated method stub
topBarFragment topBarFragment = (topBarFragment)getSupportFragmentManager().findFragmentById(R.id.topBar_fragment);
Bundle bundle = new Bundle();
bundle.putString("trackId", trackId);
//set Fragmentclass Arguments
// topBarFragment fragObject = new topBarFragment();
topBarFragment.setArguments(bundle);
topBarFragment.onTrackSelected();
}
在Activity的onTrackSelected()
方法中,兩次使用topBarFragment
。 第一個可能來自您的布局文件(或來自先前的事務)。 無論如何,第一個片段還沒有參數,但是無論如何您onTrackSelected()
調用onTrackSelected()
。 您應該將通話放在最后。
並檢查為什么還要在方法末尾重新創建它(與該問題無關,但可能不必要)。
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