如何与listview项目进行交互

Question

我正在尝试与ListView中的CheckBox实例进行交互。我创建了一个CheckBox数组，将ListView中的CheckBox项复制到它，然后创建了一个公共方法 - checkIfNull - 来获取这个数组，但是它表示数组中的所有元素都是null。你能帮我解决这个问题吗？下面是我的ListAtapter代码，它扩展了BaseAdapte，主要活动和listview的布局。

提前谢谢

<TableLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">
    <TableRow android:id="@+id/tableRow1" 
        android:layout_width="wrap_content" android:layout_height="wrap_content">

    <CheckBox android:layout_height="wrap_content" android:layout_width="wrap_content" 
        android:id="@+id/checkBox1" />
    <TwoLineListItem android:id="@+id/twoLineListItem1" 
        android:layout_weight="1"
        android:paddingTop="10px"
        android:layout_width="wrap_content" android:layout_height="wrap_content">
        <TextView android:id="@+id/textView1" 
                android:text="TextView"
                android:layout_width="wrap_content" android:layout_height="wrap_content" 
                android:textAppearance="?android:attr/textAppearanceMedium" />
        <TextView android:id="@+id/textView2" 
                android:text="TextView"
                android:layout_width="wrap_content" android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceSmall" 
                android:paddingTop="30px"/>
    </TwoLineListItem>
    <TextView android:text="TextView" 
        android:id="@+id/textView3" 
        android:layout_weight="1"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:paddingTop="10px"/>
    <RadioButton android:id="@+id/radioButton1" 
            android:gravity="center|center_vertical"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
    </TableRow>
</TableLayout>

public class ListViewSampleMain extends ListActivity {
    private String[] list1 = {"Lionel Messi", "Kai Hansen", "Jim Carrey","Christoper Nolan",
            "ABC", "Persona", "Shawdow and Collosuss"};
    private String[] list2 = {"Argentina", "Germany", "Canada", "U.S.A.", 
            "Unknown", "Japan", "Ico"};
    private String[] list3 = {"March 2nd", "January 22th", "December 15th", "Februray 1st",
            "May 4th", "August 23th", "July 17th"};

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    createListViewWithListActivity();        
}

private void createListViewWithListActivity(){
    ListAdapter listAdapter = new ListAdapter(this, list1, list2, list3);
    this.setListAdapter(listAdapter);
    listAdapter.checkIfNull();
}




public class ListAdapter extends BaseAdapter {
    private Context mContext;
    private String[] list1;
    private String[] list2;
    private String[] list3;
    private static LayoutInflater layoutInflater = null;
    private CheckBox[] cb_list;

public ListAdapter(Context context, 
        String[] list1, String[] list2, String[] list3){
    this.mContext = context;
    this.list1 = list1;
    this.list2 = list2;
    this.list3 = list3;
    ListAdapter.layoutInflater =
        (LayoutInflater)this.mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    cb_list = new CheckBox[list1.length];
}

public int getCount() {
    // TODO Auto-generated method stub
    return list1.length;
}

public Object getItem(int arg0) {
    // TODO Auto-generated method stub
    return arg0;
}

public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;
}

public View getView(int position, View convertView, ViewGroup parent) {
    View view = convertView;
    ViewHolder viewHolder;

    // To interact with OnClickListener()
    final int pos = position;

    if(convertView == null){ // check if convertView exists
        view = layoutInflater.inflate(R.layout.listview_layout, null);

        viewHolder = new ViewHolder();
        viewHolder.tv1 = (TextView)view.findViewById(R.id.textView1);
        viewHolder.tv2 = (TextView)view.findViewById(R.id.textView2);
        viewHolder.tv3 = (TextView)view.findViewById(R.id.textView3);
        viewHolder.cb = (CheckBox)view.findViewById(R.id.checkBox1);

        viewHolder.cb.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                Toast.makeText(mContext, "You clicked: "+pos, Toast.LENGTH_SHORT).show();
            }
        });

        cb_list[position] = (CheckBox) view.findViewById(R.id.checkBox1);

        view.setTag(viewHolder);
    }
    else{
        viewHolder = (ViewHolder)view.getTag();
    }
    viewHolder.tv1.setText(this.list1[position]);
    viewHolder.tv2.setText(this.list2[position]);
    viewHolder.tv3.setText(this.list3[position]);

    return view;
}

public void checkIfNull(){
    for(int i=0; i<cb_list.length; i++){
        if (cb_list[i] == null)
            Log.d("checkIfNull method", "cb_list["+i+"] is null");
        else if (cb_list[i] != null)
            Log.d("checkIfNull method", "cb_list["+i+"] is not null");
    }
}

public static class ViewHolder{
    public TextView tv1;
    public TextView tv2;
    public TextView tv3;
    public CheckBox cb;
}

/** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); createListViewWithListActivity(); } private void createListViewWithListActivity(){ ListAdapter listAdapter = new ListAdapter(this, list1, list2, list3); this.setListAdapter(listAdapter); listAdapter.checkIfNull(); }

public ListAdapter(Context context, String[] list1, String[] list2, String[] list3){ this.mContext = context; this.list1 = list1; this.list2 = list2; this.list3 = list3; ListAdapter.layoutInflater = (LayoutInflater)this.mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); cb_list = new CheckBox[list1.length]; } public int getCount() { // TODO Auto-generated method stub return list1.length; } public Object getItem(int arg0) { // TODO Auto-generated method stub return arg0; } public long getItemId(int position) { // TODO Auto-generated method stub return position; } public View getView(int position, View convertView, ViewGroup parent) { View view = convertView; ViewHolder viewHolder; // To interact with OnClickListener() final int pos = position; if(convertView == null){ // check if convertView exists view = layoutInflater.inflate(R.layout.listview_layout, null); viewHolder = new ViewHolder(); viewHolder.tv1 = (TextView)view.findViewById(R.id.textView1); viewHolder.tv2 = (TextView)view.findViewById(R.id.textView2); viewHolder.tv3 = (TextView)view.findViewById(R.id.textView3); viewHolder.cb = (CheckBox)view.findViewById(R.id.checkBox1); viewHolder.cb.setOnClickListener(new OnClickListener(){ public void onClick(View v) { Toast.makeText(mContext, "You clicked: "+pos, Toast.LENGTH_SHORT).show(); } }); cb_list[position] = (CheckBox) view.findViewById(R.id.checkBox1); view.setTag(viewHolder); } else{ viewHolder = (ViewHolder)view.getTag(); } viewHolder.tv1.setText(this.list1[position]); viewHolder.tv2.setText(this.list2[position]); viewHolder.tv3.setText(this.list3[position]); return view; } public void checkIfNull(){ for(int i=0; i<cb_list.length; i++){ if (cb_list[i] == null) Log.d("checkIfNull method", "cb_list["+i+"] is null"); else if (cb_list[i] != null) Log.d("checkIfNull method", "cb_list["+i+"] is not null"); } } public static class ViewHolder{ public TextView tv1; public TextView tv2; public TextView tv3; public CheckBox cb; }

Answer 1

为什么要选中null的复选框？您将检查复选框是“true”选中还是“false”未选中。