我在屏幕左侧有一个列表视图，单击项目时我想更新屏幕右半部分的文本，我在这里要做的是将单击的项目移动到中心列表显示。就像如果该项目在顶部并且我单击它它会自动移动到列表视图的中心，我该怎么做？任何形式的帮助将不胜感激。
我有一个列表视图，其中 7 个项目是可见的，并且在启动时将选择第 4 个项目，因为它位于列表视图中可见项目的中心，如果有 n 个项目并且用户选择的任何项目都将位于中心列表视图中的可见项目。就像我有 10 个项目，并且在开始时选择了第 4 个项目，当用户选择第 3 个项目时，listview 中的第 n 个项目应该指向索引零，第 3 个项目将出现在第 4 位。对于每个其他选定的项目也是如此？任何人都可以为此提供代码sn-p吗？
【问题讨论】：
在ListView 源Array 中更改项目顺序，然后在ListView Adapter 中调用notifyDataSetChanged()
编辑：代码示例
public class ListAdapter extends BaseAdapter{
private Activity activity;
private ArrayList<ListRowObject> listItems;
public ListAdapter(Activity activity){
this.activity = activity;
listItems = new ArrayList<ListRowObject>();
}
public void addItem(ListRowObject item){
listItems.add(item);
notifyDataSetChanged();
}
public void addItems(ArrayList<ListRowObject> items){
listItems = items;
notifyDataSetChanged();
}
public void clear(){
listItems = null;
listItems = new ArrayList<ListRowObject>();
notifyDataSetChanged();
}
@Override
public int getCount() {
return listItems.size();
}
@Override
public Object getItem(int position) {
return listItems.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup viewGroup) {
ViewHolder holder;
if(convertView == null){
holder = new ViewHolder();
convertView = activity.getLayoutInflater().inflate(R.layout.list_row, null);
holder.text = (TextView) convertView.findViewById(R.id.text);
holder.bgLayout = (LinearLayout) convertView.findViewById(R.id.bgLayout);
convertView.setTag(holder);
}else{
holder = (ViewHolder) convertView.getTag();
}
ListRowObject row = listItems.get(position);
if(row.isSelected())
holder.bgLayout.setBackgroundColor(Color.GRAY);
else
holder.bgLayout.setBackgroundColor(Color.WHITE);
holder.text.setText(row.getText());
return convertView;
}
}
//--------
public class ListRowObject {
private String text;
private int positionInList;
private boolean isSelected;
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public int getPositionInList() {
return positionInList;
}
public void setPositionInList(int positionInList) {
this.positionInList = positionInList;
}
public boolean isSelected() {
return isSelected;
}
public void setSelected(boolean selected) {
isSelected = selected;
}
}
//------
public class Main extends Activity {
private ListView listView;
private ListAdapter adapter;
private Activity activity;
private ArrayList<ListRowObject> items;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
activity = this;
initializeFormViews();
initializeOnClickEvents();
fillList();
}
private void initializeFormViews(){
listView = (ListView) findViewById(R.id.listView);
}
private void initializeOnClickEvents(){
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
Toast.makeText(activity, "Pressed " +position, Toast.LENGTH_SHORT).show();
// unselect all rows
for(ListRowObject item : items){
item.setSelected(false);
}
int first = adapterView.getFirstVisiblePosition();
int last = adapterView.getLastVisiblePosition();
int centerPosition = (first + last) / 2;
// change bg for centerPosition row
adapterView.getChildAt(centerPosition).findViewById(R.id.bgLayout).setBackgroundColor(Color.GRAY);
changeItems(position, centerPosition);
}
});
}
private void changeItems(int pressedPosition, int centerPosition){
ListRowObject centerRow = items.get(centerPosition);
ListRowObject pressedRow = items.get(pressedPosition);
pressedRow.setSelected(true);
centerRow.setSelected(false);
items.remove(centerPosition);
items.add(centerPosition, pressedRow);
items.remove(pressedPosition);
items.add(pressedPosition, centerRow);
adapter.clear();
adapter.addItems(items);
}
private void fillList(){
adapter = new ListAdapter(activity);
items = new ArrayList<ListRowObject>();
items = getItems();
for(ListRowObject item : items){
adapter.addItem(item);
}
listView.setAdapter(adapter);
}
private ArrayList<ListRowObject> getItems(){
ArrayList<ListRowObject> result = new ArrayList<ListRowObject>();
for(int i = 0; i < 15; i++){
ListRowObject object = new ListRowObject();
object.setPositionInList(i);
object.setText("Item #" + i);
if(i != 4)
object.setSelected(false);
else
object.setSelected(true);
result.add(object);
}
return result;
}
}
//------
public class ViewHolder {
public TextView text;
public LinearLayout bgLayout;
}
list_row.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="50dp"
android:id="@+id/bgLayout">
<TextView
android:layout_width="match_parent"
android:layout_height="50dp"
android:id="@+id/text"
android:textColor="#000000"
android:textSize="24dp"
android:gravity="center"/>
</LinearLayout>
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listView"/>
</LinearLayout>
【讨论】：
当您为您的列表视图创建 ArrayAdapter 时，您会向它发送一个 ListArray。当您想要更改内容时。您只需更改此 listArray，然后当单击您的项目时，您可以更改 ListArray 并调用 notifyDataSetChanged();方法你的适配器。
【讨论】：