在任何 Listview 中,视图都被重用。当您滚动浏览列表时,那些向上滚动和离开屏幕的内容将被回收并与下面的更新信息一起使用。
您需要使用稀疏数组跟踪您的复选框。当用户触摸每个索引时,将数组中的索引标记为 cherked/unchecked。然后根据数组中的值设置复选框的状态。
这是来自旧应用程序的一些示例代码,它同时执行“全选”复选框以及管理已选中和未选中的整个列表。这是我写的一个课堂考勤应用程序,所以老师更容易选择“所有”在课堂上,然后取消选择那些不在场的人。
我在此列表视图中有两个复选框,以及两个稀疏数组 itemCheckedHere 和 itemCheckedLate(学生是否在课堂上或迟到)。
public class MyDataAdapter extends SimpleCursorAdapter {
private Cursor c;
private Context context;
private Long classnum;
private gradeBookDbAdapter mDbHelper;
public static final int LATE=2;
public static final int ATTEND=1;
int idxCol;
int idx;
// itemChecked will store the position of the checked items.
public MyDataAdapter(Context context, int layout, Cursor c, String[] from,
int[] to, Long mRowId) {
super(context, layout, c, from, to);
this.c = c;
this.context = context;
mDbHelper = new gradeBookDbAdapter(context);
mDbHelper.open();
classnum = mRowId;
c.moveToFirst();
}
public class ViewHolder{
public TextView text;
public TextView text2;
public ImageView image;
public CheckBox here;
public CheckBox late;
}
public View getView(final int pos, View inView, ViewGroup parent) {
Bitmap bm;
ImageView studentPhoto;
View vi=inView;
final ViewHolder holder;
if (inView == null) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
vi = inflater.inflate(R.layout.show_attendance, null);
holder=new ViewHolder();
holder.text=(TextView)vi.findViewById(R.id.stuname);
holder.text2=(TextView)vi.findViewById(R.id.stuIndex);
holder.image=(ImageView)vi.findViewById(R.id.icon);
holder.here=(CheckBox)vi.findViewById(R.id.attend);
holder.late=(CheckBox)vi.findViewById(R.id.late);
vi.setTag(holder);
}
else
holder=(ViewHolder)vi.getTag();
c.moveToPosition(pos);
int index = c.getColumnIndex(gradeBookDbAdapter.KEY_NAME);
String name = c.getString(index);
holder.text.setText(name);
index = c.getColumnIndex(gradeBookDbAdapter.KEY_ROWID);
String Index = c.getString(index);
holder.text2.setText(Index);
bm = gradeBookDbAdapter.getStudentPhoto(name);
if (bm != null) {
holder.image.setImageBitmap(bm);
}
else {
// use icon image
holder.image.setImageResource(R.drawable.person_icon);
}
// pull out existing attend/late fields and set accordingly
int attend = c.getInt(c.getColumnIndex(gradeBookDbAdapter.KEY_ATTEND));
if(attend==1){
holder.here.setChecked(true);
itemCheckedHere.set(pos, true);
}
//else {
// holder.here.setChecked(false);
// itemCheckedHere.set(pos, false);
//}
int late = c.getInt(c.getColumnIndex(gradeBookDbAdapter.KEY_LATE));
if (late==1){
holder.late.setChecked(true);
itemCheckedLate.set(pos, true);
}
//else {
// holder.late.setChecked(false);
// itemCheckedLate.set(pos, false);
//}
if (selectAllTouched) {
if(selectAll){
holder.here.setChecked(true);
itemCheckedHere.set(pos, true);
int who= new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(who, classnum, ATTEND, 1, attendDate );
}
else{
holder.here.setChecked(false);
itemCheckedHere.set(pos, false);
int who = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(who, classnum, ATTEND, 0, attendDate );
}
}
holder.here.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
CheckBox cb = (CheckBox) v.findViewById(R.id.attend);
if (cb.isChecked()) {
itemCheckedHere.set(pos, true);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, ATTEND, 1, attendDate );
} else if (!cb.isChecked()) {
itemCheckedHere.set(pos, false);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, ATTEND, 0, attendDate );
}
}
});
holder.late.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
CheckBox cb = (CheckBox) v.findViewById(R.id.late);
if (cb.isChecked()) {
itemCheckedLate.set(pos, true);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, LATE, 1, attendDate );
} else if (!cb.isChecked()) {
itemCheckedLate.set(pos, false);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, LATE, 0, attendDate );
}
}
});
holder.here.setChecked(itemCheckedHere.get(pos)); // this will Check or Uncheck the
holder.late.setChecked(itemCheckedLate.get(pos)); // this will Check or Uncheck the
// CheckBox in ListView
// according to their original
// position and CheckBox never
// loss his State when you
// Scroll the List Items.
return vi;
}
}
}