无法设置OnCheckedChangeListener一个复选框 [英] Can't set OnCheckedChangeListener to a Checkbox

问题描述

我想设定一个 OnCheckedChangeListener 到复选框，但我的应用程序在运行时退出。我也试着设置监听我的的TextView ，我仍然得到同样的结果。任何人都可以帮忙吗？

 进口android.app.ListActivity;
进口android.content.Context;
进口android.content.DialogInterface;
进口android.content.DialogInterface.OnClickListener;
进口android.os.Bundle;
进口android.view.LayoutInflater;
进口android.view.View;
进口android.view.ViewGroup;
进口android.widget.AdapterView;
进口android.widget.AdapterView.OnItemClickListener;
进口android.widget.ArrayAdapter;
进口android.widget.CheckBox;
进口android.widget.CompoundButton;
进口android.widget.CompoundButton.OnCheckedChangeListener;
进口android.widget.ImageView;
进口android.widget.ListView;
进口android.widget.TextView;
进口android.widget.Toast;

公共类ListViewActivity扩展ListActivity实现OnCheckedChangeListener {

TextView的标签;
复选框复选框;

公共类MyCustomAdapter扩展ArrayAdapter＆LT;字符串＆GT; {


公共MyCustomAdapter（上下文的背景下，INT textViewResourceId，
的String []对象）{
超（背景下，textViewResourceId，对象）;

 // TODO自动生成构造函数存根
}

@覆盖
公共查看getView（INT位置，查看convertView，ViewGroup中父）{
// TODO自动生成方法存根
//返回super.getView（位置，convertView，父母）;

查看排= convertView;

如果（行== NULL）{
LayoutInflater充气= getLayoutInflater（）;
行= inflater.inflate（R.layout.main，父母，假）;

}


标签=（TextView中）row.findViewById（R.id.weekofday）;
label.setText（月[位置]）;
复选框=（复选框）row.findViewById（R.id.checkBox）;


返回行;
}
}

的String []月= {
月，月，月，月，
五一，六一，七一，八一，
九·一，十月，月，月
};

 / **第一次创建活动时调用。 * /
 @覆盖
 公共无效的onCreate（包savedInstanceState）{
 super.onCreate（savedInstanceState）;
//的setContentView（R.layout.main）;
 / * setListAdapter（新ArrayAdapter＆LT;字符串＆GT;（这一点，
   R.layout.row，R.id.weekofday，星期几））; * /


   setListAdapter（新MyCustomAdapter（ListViewActivity.this，R.layout.main，一个月））;

   checkBox.setOnCheckedChangeListener（本）; //我的应用程序退出这里!!!!

 }





@覆盖
公共无效onCheckedChanged（CompoundButton为arg0，布尔ARG1）{
// TODO自动生成方法存根
//Toast.makeText（getApplicationContext（）中选中，Toast.LENGTH_LONG）;

}


}
 

解决方案

您不能设置监听你的复选框从的ListView 这样的（它可能会抛出一个 NullPointerException异常），而不是设置在 getView（）办法（你也必须保持复选框状态，这样你就不会结束与陌生行状态）。贝娄是一个例子：

 公共类ListViewActivity扩展ListActivity {

    公共类MyCustomAdapter扩展ArrayAdapter＆LT;字符串＆GT; {

        私人的ArrayList＆LT;布尔＆GT;状态=新的ArrayList＆LT;布尔＆GT;（）;

        公共MyCustomAdapter（上下文的背景下，INT textViewResourceId，
                的String []对象）{
            超（背景下，textViewResourceId，对象）;
            的for（int i = 0; I＆LT; objects.length;我++）{
                status.add（假）;
            }
        }

        @覆盖
        公共查看getView（最终诠释的立场，观点convertView，
                ViewGroup中父）{
            查看排= convertView;
            如果（行== NULL）{
                LayoutInflater充气= getLayoutInflater（）;
                行= inflater.inflate（R.layout.adapters_listviewactivity_row，
                        父母，假）;
            }

            TextView的标签=（TextView中）row.findViewById（R.id.weekofday）;
            label.setText（月[位置]）;
            复选框复选框=（复选框）row.findViewById（R.id.checkBox）;
            checkBox.setOnCheckedChangeListener（新OnCheckedChangeListener（）{

                @覆盖
                公共无效onCheckedChanged（CompoundButton buttonView，
                        布尔器isChecked）{
                    Toast.makeText（getApplicationContext（），+位置，
                            Toast.LENGTH_SHORT）.show（）;
                    如果（器isChecked）{
                        status.set（位置，真正的）;
                    } 其他 {
                        status.set（位置，假）;
                    }
                }
            }）;
            checkBox.setChecked（status.get（位置））;
            返回行;
        }
    }

    的String []月= {一月，二月，月，月，五一，六一，
            七五，八五，九五，十月，月，十二月};

    / **第一次创建活动时调用。 * /
    @覆盖
    公共无效的onCreate（包savedInstanceState）{
        super.onCreate（savedInstanceState）;
        setListAdapter（新MyCustomAdapter（ListViewActivity.this，
                R.layout.main，一个月））;
    }

}
 

对于的TextView 你必须做同样的事情。

I am trying to set a OnCheckedChangeListener to a CheckBox but my application exits in the run time. I also tried to set listeners for my TextView and I still get the same result. Can anyone help?

import android.app.ListActivity;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class ListViewActivity extends ListActivity implements OnCheckedChangeListener {

TextView label;
CheckBox checkBox;

public class MyCustomAdapter extends ArrayAdapter<String> {


public MyCustomAdapter(Context context, int textViewResourceId,
String[] objects) {
super(context, textViewResourceId, objects);

 // TODO Auto-generated constructor stub
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
//return super.getView(position, convertView, parent);

View row = convertView;

if(row==null){
LayoutInflater inflater=getLayoutInflater();
row=inflater.inflate(R.layout.main, parent, false); 

}  


label=(TextView)row.findViewById(R.id.weekofday);
label.setText(month[position]);
checkBox=(CheckBox)row.findViewById(R.id.checkBox);


return row;
}
}

String[] month = {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December"
};

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
// setContentView(R.layout.main);
 /*setListAdapter(new ArrayAdapter<String>(this,
   R.layout.row, R.id.weekofday, DayOfWeek));*/


   setListAdapter(new MyCustomAdapter(ListViewActivity.this, R.layout.main, month));

   checkBox.setOnCheckedChangeListener(this); //my application exits here!!!!

 }





@Override
public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
// TODO Auto-generated method stub
//Toast.makeText(getApplicationContext(), "box checked", Toast.LENGTH_LONG);

}


}

解决方案

You can't set the listener for your CheckBox from the ListView like that(it will probably throw a NullPointerException), instead set the listener in the getView() method(you'll also have to keep the CheckBox status so you don't end up with strange rows status). Bellow is an example:

public class ListViewActivity extends ListActivity {

    public class MyCustomAdapter extends ArrayAdapter<String> {

        private ArrayList<Boolean> status = new ArrayList<Boolean>();

        public MyCustomAdapter(Context context, int textViewResourceId,
                String[] objects) {
            super(context, textViewResourceId, objects);
            for (int i = 0; i < objects.length; i++) {
                status.add(false);
            }
        }

        @Override
        public View getView(final int position, View convertView,
                ViewGroup parent) {
            View row = convertView;
            if (row == null) {
                LayoutInflater inflater = getLayoutInflater();
                row = inflater.inflate(R.layout.adapters_listviewactivity_row,
                        parent, false);
            }

            TextView label = (TextView) row.findViewById(R.id.weekofday);
            label.setText(month[position]);
            CheckBox checkBox = (CheckBox) row.findViewById(R.id.checkBox);
            checkBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {

                @Override
                public void onCheckedChanged(CompoundButton buttonView,
                        boolean isChecked) {
                    Toast.makeText(getApplicationContext(), "" + position,
                            Toast.LENGTH_SHORT).show();
                    if (isChecked) {
                        status.set(position, true);
                    } else {
                        status.set(position, false);
                    }
                }
            });
            checkBox.setChecked(status.get(position));
            return row;
        }
    }

    String[] month = { "January", "February", "March", "April", "May", "June",
            "July", "August", "September", "October", "November", "December" };

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setListAdapter(new MyCustomAdapter(ListViewActivity.this,
                R.layout.main, month));
    }

}

For the TextView you'll have to do the same thing.

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