android - 滚动 ListView 时自动取消选中复选框

Question

我有一个带有复选框和文本框的 ListView 。当我选中复选框并上下滚动它时，它会自动取消选中。如何在 ListView 中解决这个问题？请给我解决方案。
下面是我的屏幕截图和代码。

screen shot

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lvMain"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

        <Button
            android:id="@+id/btnSelectAll"
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            android:text="Select All" >
        </Button>
    </LinearLayout>

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <CheckBox
        android:id="@+id/cbItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:buttonTint="#000000">
    </CheckBox>

    <TextView
        android:id="@+id/tvItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#000000">
    </TextView>

</LinearLayout>

MainActivity.java

package com.example.checkallcheckbox;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;

public class MainActivity extends Activity {
    ListView lvMain;
    String[] name = { "Jenis", "Pratik", "Jaydeep", "Hiren", "Himansu",
            "yagnik", "Atul", "Prakas", "Nihal", "Darshan", "Chetan", "Sagar",
            "Nikhil", "Sanket", "Rahul", "Jigar" };

    Button btnSelectAll;
    boolean isSelectAll = true;
    ListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        lvMain = (ListView) findViewById(R.id.lvMain);
        btnSelectAll = (Button) findViewById(R.id.btnSelectAll);

        btnSelectAll.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                if(isSelectAll)
                {
                adapter = new ListAdapter(getApplicationContext(), name, true);
                lvMain.setAdapter(adapter);
                adapter.notifyDataSetChanged();
                btnSelectAll.setText("ClearAll");
                isSelectAll=false;
                }
                else
                {
                    adapter = new ListAdapter(getApplicationContext(), name, false);
                    lvMain.setAdapter(adapter);
                    adapter.notifyDataSetChanged();
                    btnSelectAll.setText("CheckAll");
                    isSelectAll=true;

                }

            }
        });

        adapter = new ListAdapter(getApplicationContext(), name,false);
        lvMain.setAdapter(adapter);
        adapter.notifyDataSetChanged();

    }
}

ListAdapter.java

package com.example.checkallcheckbox;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.TextView;

public class ListAdapter extends BaseAdapter {

    Context mContext;
    String[] name;
    private static LayoutInflater inflater = null;
    Boolean state=false;

    public ListAdapter(Context c, String[] name, boolean isSelectAll) {
        // TODO Auto-generated constructor stub
        mContext = c;
        this.name = name;
        inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        state=isSelectAll;
    }

    @Override
    public int getCount() {

        return name.length;
    }

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

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

    public class ViewHolder {
        TextView tvName;
        CheckBox cbName;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup arg2) {
        // TODO Auto-generated method stub
        ViewHolder viewHolder;

        if (convertView == null) {

            convertView = inflater.inflate(R.layout.list_item, null);
            viewHolder = new ViewHolder();
            viewHolder.tvName = (TextView) convertView
                    .findViewById(R.id.tvItem);
            viewHolder.cbName = (CheckBox) convertView
                    .findViewById(R.id.cbItem);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.tvName.setText(name[position]);

        if(state){
            viewHolder.cbName.setChecked(true);
        }else{
            viewHolder.cbName.setChecked(false);
        }

        return convertView;
    }

}

Answer 1

问题是因为您的 ListView View 正在重新制作。当您将它们滚动到屏幕外时，android 不会保留它们(列表可能真的很长，所以这意味着有很多您看不到的 View )。

因此，每次您将某个项目滚动回屏幕时，Android 会再次调用 getView 并返回一个未选中复选框的 View 。

您需要做的是在每个列表项上设置一个单击/选中的监听器，以便能够记住它们何时被选中。然后当 android 向你询问 View 时，你可以检查它是否应该被检查。

您可以看到 getItem 方法已经存在，可以帮助您完成此操作。您可以尝试重写 ArrayAdapter，因为这样您就可以存储一些可以保存“已单击”状态的简单对象。请参阅:http://developer.android.com/reference/android/widget/ArrayAdapter.html

这就是为什么 Aditya 会问您模型类在哪里。目前你只有一份学生名单，你想要的是一份学生名单以及他们是否被选中。也许是这样的类(class):

class Student
{
    private String mName;
    public Boolean selected;

    public Student(String name)
    {
        mName = name;
    }

    public String getName()
    {
        return mName;
    }
}

然后你可以用这些数组代替。单击某个项目时，您将在相关学生项目上设置 selected。

您的 getView 可能如下所示:

@Override
public View getView(int position, View convertView, ViewGroup arg2) {
    // TODO Auto-generated method stub
    ViewHolder viewHolder;

    if (convertView == null) {

        convertView = inflater.inflate(R.layout.list_item, null);
        viewHolder = new ViewHolder();
        viewHolder.tvName = (TextView) convertView
                .findViewById(R.id.tvItem);
        viewHolder.cbName = (CheckBox) convertView
                .findViewById(R.id.cbItem);
        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
    }

    Student thisStudent = students[position];
    viewHolder.tvName.setText(thisStudent.getName());

    if(state || thisStudent.selected){
        viewHolder.cbName.setChecked(true);
    }else{
        viewHolder.cbName.setChecked(false);
    }

    return convertView;
}

有很多关于此的指南，这里有一个这样的指南，它解释了 View 回收在列表中的工作原理(您的问题)以及如何使用 ArrayAdapter https://github.com/codepath/android_guides/wiki/Using-an-ArrayAdapter-with-ListView