我正在尝试学习如何在 fragment 中显示具有 3 列的 GridView 。这些值来自 strings.xml 文件,以数组列表形式提供。当我运行应用程序时它崩溃了。谁能帮我显示 3 列中的值,即地点、描述和时间。我无法继续了解如何在 GridView 中显示读取的值。
My Code are as follows:
**Strings.XML**
<string-array name="PlacesName">
<item>Durban</item>
<item>Paris</item>
<item>HongKong</item>
<item>Canada</item>
</string-array>
<string-array name="Description">
<item>Description1</item>
<item>Description2</item>
<item>Description3</item>
</string-array>
<string-array name="ScheduleDate">
<item>12/1/2015</item>
<item>13/2/2015</item>
<item>14/4/2015</item>
<item>15/5/2015</item>
</string-array>
**Fragment**
*/
public class FlightFragment extends Fragment {
GridView grid;
public FlightFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_flight, container, false);
// Inflate the layout for this fragment
grid = (GridView) view.findViewById(R.id.gridView);
MyAdapter myAdapter = new MyAdapter();
grid.setAdapter(myAdapter);
return view;
}
class MyAdapter extends BaseAdapter {
ArrayList<Schedule> list;
private Context context;
MyAdapter() {
list = new ArrayList();
Resources resources = context.getResources();
String[] tempPlaces = resources.getStringArray(R.array.PlacesName);
String[] tempDate = resources.getStringArray(R.array.ScheduleDate);
String[] tempDescription = resources.getStringArray(R.array.Description);
for(int count=0;count<4;count++ ){
Schedule tempSchedule = new Schedule(tempPlaces[count],tempDate[count],tempDescription[count]);
list.add(tempSchedule);
}
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Schedule tempSchedule = list.get(position);
TextView textView;
if (convertView == null){
textView = new TextView(context);
textView.setLayoutParams(new GridView.LayoutParams(85, 85));
textView.setPadding(8, 8, 8, 8);
}
else{
textView = (TextView) convertView;
}
textView.setText(tempSchedule.Place);
return textView;
}
}
class Schedule {
String Place;
String ScheduleTime;
String Description;
Schedule(String place, String scheduleTime, String description ) {
this.Description = description;
this.Place = place;
this.ScheduleTime = scheduleTime;
}
}
}
错误
FATAL EXCEPTION: main java.lang.NullPointerException at com.ts.FlightFragment$MyAdapter.(FlightFragment.java:51) at com.ts.FlightFragment.onCreateView(FlightFragment.java:38) at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:5279) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869) at dalvik.system.NativeStart.main(Native Method)
最佳答案
问题是您忘记在适配器中分配上下文。您可以通过构造函数传递它。在 Activity 中,您可以简单地使用 this
作为上下文。在您的情况下,在 fragment 中,需要将 getActivity()
作为上下文传递。
public class FlightFragment extends Fragment {
GridView grid;
public FlightFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_flight, container, false);
// Inflate the layout for this fragment
grid = (GridView) view.findViewById(R.id.gridView);
MyAdapter myAdapter = new MyAdapter(getActivity());
grid.setAdapter(myAdapter);
return view;
}
class MyAdapter extends BaseAdapter {
ArrayList<Schedule> list;
private Context context;
MyAdapter(Context context) {
this.context = context;
list = new ArrayList();
Resources resources = context.getResources();
String[] tempPlaces = resources.getStringArray(R.array.PlacesName);
String[] tempDate = resources.getStringArray(R.array.ScheduleDate);
String[] tempDescription = resources.getStringArray(R.array.Description);
for(int count=0;count<4;count++ ){
Schedule tempSchedule = new Schedule(tempPlaces[count],tempDate[count],tempDescription[count]);
list.add(tempSchedule);
}
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Schedule tempSchedule = list.get(position);
if (convertView == null){
convertView = LayoutInflater.from(context).inflate(R.layout.grid_row, parent, false);
}
TextView placeName = (TextView) convertView.findViewById(R.id.place_name);
TextView scheduleDate = (TextView) convertView.findViewById(R.id.schedule_date);
TextView description = (TextView) convertView.findViewById(R.id.description);
placeName.setText(tempSchedule.Place);
scheduleDate.setText(tempSchedule.ScheduleTime);
description.setText(tempSchedule.Description);
return convertView;
}
}
在 grid_row.xml 中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical">
<TextView
android:id="@+id/place_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView
android:id="@+id/schedule_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView
android:id="@+id/description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
编辑
您需要创建包含 3 个 TextView 的 grid_row.xml
。在 getView
上膨胀该布局,然后返回它。
您可以通过使用 ViewHolder Pattern 来提高性能以避免 findViewById()
.
关于java - 如何在Android中的GridView中在fragment中显示ArrayList对象,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28980792/