[英]findViewById in DialogFragment - NullPointerException
我顯示的對話框有兩個Spinners,其中一個我想設置所選項目(要選擇的項目是使用setArguments()/ getArguments()從主活動傳遞的
問題是我無法獲得微調器,而是在我處獲得NullPointerException
Spinner spinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner);
DialogFragment代碼:
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Spinner;
public class DFrag extends DialogFragment
{
public Dialog onCreateDialog(Bundle savedInstanceState)
{
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
builder.setView(inflater.inflate(R.layout.activity_schedule_select_dialog, null))
.setPositiveButton(R.string.ssd_select_positive, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
mListener.onDialogPositiveClick(DFrag.this);
}
})
.setNegativeButton(R.string.select_negative, new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
mListener.onDialogNegativeClick(DFrag.this);
DFrag.this.getDialog().cancel();
}
});
builder.setInverseBackgroundForced(true);
return builder.create();
}
public void onActivityCreated(Bundle savedInstanceState)
{
View view = getView();
Spinner spinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner);
spinner.setSelection(getArguments().getInt("SelectWeek"));
super.onActivityCreated(savedInstanceState);
}
public interface DFragListener
{
public void onDialogPositiveClick(DialogFragment dialog);
public void onDialogNegativeClick(DialogFragment dialog);
}
DFragListener mListener;
@Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
try
{
mListener = (DFragListener) activity;
}
catch (ClassCastException e)
{
throw new ClassCastException(activity.toString() + " Listener not implemented");
}
}
}
根據要求,對話框的布局(activity_schedule_select_dialog.xml):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/ssd_classLabel"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/select_class_label"
android:layout_marginRight="4dip"
android:layout_marginLeft="4dip"/>
<Spinner
android:id="@+id/ssd_classSelectSpinner"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="4dip"
android:entries="@array/urnikClasses"/>
<TextView
android:id="@+id/ssd_weekLabel"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/select_week_label"
android:layout_marginRight="4dip"
android:layout_marginLeft="4dip"/>
<Spinner
android:id="@+id/ssd_weeksSelectSpinner"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:entries="@array/weeksArray"/>
<CheckBox
android:id="@+id/ssd_DefaultChkbox"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/ssd_DefaultChkBoxTxt"/>
</LinearLayout>
logcat的:
05-12 13:16:16.288: E/AndroidRuntime(4310): FATAL EXCEPTION: main
05-12 13:16:16.288: E/AndroidRuntime(4310): java.lang.NullPointerException
05-12 13:16:16.288: E/AndroidRuntime(4310): at com.rogy.scks.urnik.DFrag.onActivityCreated(DFrag.java:91)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1468)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:931)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:429)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.os.Handler.handleCallback(Handler.java:725)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.os.Handler.dispatchMessage(Handler.java:92)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.os.Looper.loop(Looper.java:137)
05-12 13:16:16.288: E/AndroidRuntime(4310): at android.app.ActivityThread.main(ActivityThread.java:5195)
05-12 13:16:16.288: E/AndroidRuntime(4310): at java.lang.reflect.Method.invokeNative(Native Method)
05-12 13:16:16.288: E/AndroidRuntime(4310): at java.lang.reflect.Method.invoke(Method.java:511)
05-12 13:16:16.288: E/AndroidRuntime(4310): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-12 13:16:16.288: E/AndroidRuntime(4310): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-12 13:16:16.288: E/AndroidRuntime(4310): at dalvik.system.NativeStart.main(Native Method)
找到解決方案,而不是試圖在public void onActivityCreated(Bundle savedInstanceState)
找到視圖
在public Dialog onCreateDialog(Bundle savedInstanceState)
我改變了
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
builder.setView(inflater.inflate(R.layout.activity_schedule_select_dialog, null))
.setPositiveButton(R.string.ssd_select_positive, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
mListener.onDialogPositiveClick(DFrag.this);
}
})
.setNegativeButton(R.string.select_negative, new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
mListener.onDialogNegativeClick(DFrag.this);
DFrag.this.getDialog().cancel();
}
});
至
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.activity_schedule_select_dialog, null);
builder.setView(view)
.setPositiveButton(R.string.ssd_select_positive, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
mListener.onDialogPositiveClick(DFrag.this);
}
})
.setNegativeButton(R.string.select_negative, new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
mListener.onDialogNegativeClick(DFrag.this);
DFrag.this.getDialog().cancel();
}
});
並在最后添加
Spinner spinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner);
spinner.setSelection(getArguments().getInt("SelectWeek"));
首先將Spinner對象提取到類的成員中。
public class DFrag extends DialogFragment
{
private Spinner mSpinner;
...
然后從onCreateDialog()函數中指定微調器
public Dialog onCreateDialog(Bundle savedInstanceState)
{
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.activity_schedule_select_dialog, null);
// Assign spinner
mSpinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner);
builder.setView(view);
// Set positive and negative buttons here
...
}
現在將微調器的值放在onCreateView()函數上
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
mSpinner.setSelection(getArguments().getInt("SelectWeek"));
...
}
干杯!
這是由於:
public void onActivityCreated(Bundle savedInstanceState) { View view = getView(); Spinner spinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner); spinner.setSelection(getArguments().getInt("SelectWeek")); super.onActivityCreated(savedInstanceState); }
它給你一個NullPointerException,因為當活動開始時,它沒有被選中並且它是空的...你需要把它放在onItemSelected監聽器上。
public class SpinnerActivity extends Activity implements OnItemSelectedListener {
...
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
// An item was selected. You can retrieve the selected item using
// parent.getItemAtPosition(pos)
}
public void onNothingSelected(AdapterView<?> parent) {
// Another interface callback
}
}
有關詳細信息,請參閱此處 : http : //developer.android.com/guide/topics/ui/controls/spinner.html#SelectListener
編輯:你還需要導入“R”java文件..我沒有在導入列表上看到它:
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Spinner;
編輯2:要向微調器添加偵聽器,請執行以下操作:
Spinner spinner = (Spinner) view.findViewById(R.id.ssd_weeksSelectSpinner);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> arg0, View v, int position, long id)
{
// int position is the element you pressed
}
});
這也可以使用Kotlin優雅地完成:
lateinit val myView: View;
override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
return AlertDialog.Builder(activity!!)
.setPositiveButton(R.string.close) { dialog, which -> }
.setView(LayoutInflater.from(activity).inflate(R.layout.my_fragment, null, false).apply {
this@MyDialogFragment.myview = findViewById(R.id.my_view)
})
.create()
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
//do something with myView
}
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