Android 如何从 ListView 中提取对象 - getItemAtPosition 不起作用
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How to extract objects from ListView - getItemAtPosition won't work
提问by Harsh
I've a custom adapter implemented for my ListView. How do I extract objects from a particular list item. Here's how my custom adapter looks:
我为我的ListView. 如何从特定列表项中提取对象。这是我的自定义适配器的外观：
MyCustomAdapter.java
我的自定义适配器.java
public class MyCustomAdapter extends ArrayAdapter<DashboardBean> {
Context context;
int layoutResourceId;
DashboardBean currentMRB;
Vector<DashboardBean> data;
public MyCustomAdapter(Context context, int layoutResourceId, Vector<DashboardBean> data)
{
super(context,layoutResourceId,data);
this.layoutResourceId = layoutResourceId;
this.context=context;
this.data = data;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
MyStringReaderHolder holder;
if(row==null)
{
LayoutInflater inflater = ((Activity)context).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent,false);
holder= new MyStringReaderHolder();
holder.project = (TextView)row.findViewById(R.id.project);
holder.workRequest = (TextView)row.findViewById(R.id.work_request);
holder.startDate = (TextView)row.findViewById(R.id.start_date);
holder.status = (TextView) row.findViewById(R.id.status);
row.setTag(holder);
}
else
{
holder=(MyStringReaderHolder) row.getTag();
}
DashboardBean mrb =data.elementAt(position);
System.out.println("Position="+position);
holder.project.setText(mrb.project);
holder.workRequest.setText(mrb.workRequest);
holder.startDate.setText(mrb.startDate);
holder.status.setText(mrb.status);
return row;
}
static class MyStringReaderHolder {
TextView project, workRequest, startDate, status;
}
}
Here's the DashboardBean.java
这是 DashboardBean.java
public class DashboardBean {
public String project;
public String workRequest;
public String startDate;
public String status;
public DashboardBean(String project,String workRequest,String startDate,String status)
{
this.project = project;
this.workRequest = workRequest;
this.startDate = startDate;
this.status = status;
}
}
Here's java snippet from where I call onClickListener() :
这是我调用 onClickListener() 的 java 片段：
mListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> myAdapter, View myView,
int myItemInt, long mylng) {
TableRow tableRow = (TableRow) (mListView.getItemAtPosition(myItemInt));
String project = ((TextView) tableRow.findViewById(R.id.project)).getText().toString();
String workRequest = ((TextView) tableRow.findViewById(R.id.work_request)).getText().toString();
String startDate = ((TextView) tableRow.findViewById(R.id.start_date)).getText().toString();
String status = ((TextView) tableRow.findViewById(R.id.status)).getText().toString();
showWorkRequest(project, workRequest, startDate, status);
}
});
And the xml code:
和 xml 代码：
<?xml version="1.0" encoding="utf-8"?>
<TableRow xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/tabRow1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
style="@style/BodyRow"
android:gravity="center_horizontal" >
<RelativeLayout
android:id="@+id/relativeLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_horizontal" >
<TextView
android:id="@+id/status"
android:layout_width="wrap_content"
style="@style/BodyText"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:textColor="@color/textColor"
android:text="TextView" />
<TextView
android:id="@+id/start_date"
style="@style/HourText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="TextView" android:textColor="@color/textColor" android:textSize="10sp"/>
<TextView
android:id="@+id/project"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_toRightOf="@+id/start_date"
android:gravity="center_horizontal"
style="@style/LeftHeaderText"
android:text="TextView" android:layout_marginLeft="5dp"
android:textColor="@color/textColor" android:textStyle="bold"/>
<TextView
android:id="@+id/work_request"
android:layout_width="wrap_content"
style="@style/BodyText"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/project"
android:layout_below="@+id/project"
android:text="TextView"
android:textColor="@color/textColor" />
</RelativeLayout>
</TableRow>
I guess I can't use onClickListener as it is usually used because I'm extendind custom adapter. In that case they may be a problem with
我想我不能使用通常使用的 onClickListener，因为我扩展了自定义适配器。在这种情况下，他们可能会遇到问题
public void onItemClick(AdapterView<?> myAdapter, View myView,
int myItemInt, long mylng)
But the log says: ClassCastException at DashboardBean.
但是日志说：DashboardBean 的 ClassCastException。
Anyway, I can't fix it. Could anyone help?
无论如何，我无法解决它。有人可以帮忙吗？
回答by Giulio Piancastelli
The ClassCastExceptionis caused by the following line in your OnItemClickListener:
这ClassCastException是由您的以下行引起的OnItemClickListener：
TableRow tableRow = (TableRow) (mListView.getItemAtPosition(myItemInt));
And that's because your adapter is filled with DashboardBeaninstances. The getItemAtPositionmethod returns an object belonging to the data structure the adapter works with, notan instance of the graphic widget (TableRow, I assume) which the object is shown on. Just writing:
那是因为您的适配器充满了DashboardBean实例。该getItemAtPosition方法返回一个属于适配器使用的数据结构的对象，而不是TableRow显示该对象的图形小部件（我假设为 ）的实例。只是写：
DashboardBean board = (DashboardBean) (mListView.getItemAtPosition(myItemInt));
in place of the offending line would do the trick. You can then work directly with the fields in the DashboardBeanobject instead of passing through TextViews and similar UI elements.
代替违规行就可以了。然后您可以直接使用DashboardBean对象中的字段，而不是通过TextViews 和类似的 UI 元素。
回答by Jules Colle
You should be able to get your DashboardBean object in onItemclick like this:
您应该能够像这样在 onItemclick 中获取 DashboardBean 对象：
DashboardBean bean = (DashboardBean) mListView.getItemAtPosition(myItemInt);
回答by Vipul Shah
If you just want to extract object then OnItemClickListenermakes your task easier.You ger view instance of the row.from that you can extract the contents.
如果您只想提取对象，那么OnItemClickListener您的任务就更容易了。您可以查看行的实例。从中您可以提取内容。
Change
改变
mListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> myAdapter, View myView,
int myItemInt, long mylng) {
TableRow tableRow = (TableRow) (mListView.getItemAtPosition(myItemInt));
String project = ((TextView) tableRow.findViewById(R.id.project)).getText().toString();
String workRequest = ((TextView) tableRow.findViewById(R.id.work_request)).getText().toString();
String startDate = ((TextView) tableRow.findViewById(R.id.start_date)).getText().toString();
String status = ((TextView) tableRow.findViewById(R.id.status)).getText().toString();
showWorkRequest(project, workRequest, startDate, status);
}
});
To This
至此
mListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView <? > myAdapter, View myView, int myItemInt, long mylng) {
String project = ((TextView) myView.findViewById(R.id.project)).getText().toString();
String workRequest = ((TextView) myView.findViewById(R.id.work_request)).getText().toString();
String startDate = ((TextView) myView.findViewById(R.id.start_date)).getText().toString();
String status = ((TextView) myView.findViewById(R.id.status)).getText().toString();
showWorkRequest(project, workRequest, startDate, status);
}
});
