Question

我有自定义列表视图和自定义适配器。布局如下：

enter image description here

现在，我有一个默认隐藏的复选框（在customlistlayout中定义）。我希望它在用户按下删除按钮时显示。

我尝试在按钮onclicklistener中设置setVisibility(View.VISIBLE);，但应用程序崩溃了。我怎样才能做到这一点。感谢您的帮助

Log Cat`12-23 22:27:54.236: E/AndroidRuntime(18681): FATAL EXCEPTION: main
12-23 22:27:54.236: E/AndroidRuntime(18681): Process: com.testing.callreminder, PID: 18681
12-23 22:27:54.236: E/AndroidRuntime(18681): java.lang.NullPointerException
12-23 22:27:54.236: E/AndroidRuntime(18681):    at com.testing.callreminder.MainActivity.onClick(MainActivity.java:130)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at android.view.View.performClick(View.java:4633)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at android.view.View$PerformClick.run(View.java:19330)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at android.os.Handler.handleCallback(Handler.java:733)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at android.os.Handler.dispatchMessage(Handler.java:95)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at android.app.ActivityThread.main(ActivityThread.java:5356)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at java.lang.reflect.Method.invokeNative(Native Method)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at java.lang.reflect.Method.invoke(Method.java:515)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
12-23 22:27:54.236: E/AndroidRuntime(18681):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)

布局的OnClickListener实现：

public void onClick(View v) {
    // TODO Auto-generated method stub

    switch(v.getId())
    {
    case R.id.btn_add :
        Intent next = new Intent("com.testing.callreminder.ADDITEM");
        startActivity(next);

        break;
    case R.id.btn_delete:
        chk.setVisibility(View.VISIBLE);
        break;


    default:
        chk.setVisibility(View.GONE);
        break;

    }       
}

CustomAdapter

public class MenuListAdapter extends BaseAdapter {
    boolean i;
    Context c;
    ArrayList<MenuListItems> menuList;

    public MenuListAdapter(Context context, ArrayList<MenuListItems> list){
        c=context;
        menuList=list;
    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return menuList.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return menuList.get(position);

    }

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

    public void setCheckBoxVisibility(boolean visible) {
        i = visible;


    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        MenuListItems menuListItems = menuList.get(position);

          if (convertView == null) {
               LayoutInflater inflater = (LayoutInflater) c
                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
               convertView = inflater.inflate(R.layout.customlist, parent, false);

              }
          if(i){
              CheckBox ck = (CheckBox) convertView.findViewById(R.id.delBox);
              ck.setVisibility(View.VISIBLE);
              notifyDataSetChanged();

          }
                TextView id = (TextView) convertView.findViewById(R.id.tvhide);
                id.setText(menuListItems.getSlno());
              TextView title = (TextView) convertView.findViewById(R.id.tvtitle);
              title.setText(menuListItems.getTitle());
              TextView phone = (TextView) convertView.findViewById(R.id.tvpnumber);
              phone.setText(menuListItems.getPhone());

              return convertView;
        }
}

Answer 1

在适配器上创建一个方法，例如＆＃34; setCheckBoxVisibility（boolean visible）;＆＃34;在此方法中，您将布尔值保存到私有字段中并调用notifyDataSetChanged（）;在getView方法中，您将检查此字段并设置可见性。

public class MenuListAdapter extends BaseAdapter {
boolean i;
boolean showCheckbox;
Context c;
ArrayList<MenuListItems> menuList;

public MenuListAdapter(Context context, ArrayList<MenuListItems> list){
    c=context;
    menuList=list;
}
@Override
public int getCount() {
    // TODO Auto-generated method stub
    return menuList.size();
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return menuList.get(position);

}

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

public void setCheckBoxVisibility(boolean visible) {
    i = visible;
    notifyDataSetChanged(); //notify dataset changed here

}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    MenuListItems menuListItems = menuList.get(position);

      if (convertView == null) {
           LayoutInflater inflater = (LayoutInflater) c
             .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
           convertView = inflater.inflate(R.layout.customlist, parent, false);

          }
      if(i){
          CheckBox ck = (CheckBox) convertView.findViewById(R.id.delBox);

          if(i)
              ck.setVisibility(View.VISIBLE);
          else
              ck.setVisibility(View.GONE);
      }
            TextView id = (TextView) convertView.findViewById(R.id.tvhide);
            id.setText(menuListItems.getSlno());
          TextView title = (TextView) convertView.findViewById(R.id.tvtitle);
          title.setText(menuListItems.getTitle());
          TextView phone = (TextView) convertView.findViewById(R.id.tvpnumber);
          phone.setText(menuListItems.getPhone());

          return convertView;
    }
    }

单击按钮时的ListView自定义

1 个答案: