最近在写Android界面时经常用到listview这个控件,个人认为其缺陷很多,比如快速滑动时,会出现加载缓慢,不能缓存加载过得数据,每次滑动时都要加载控件的ID,所以须有将listview优化,下面将讲讲我遇到的问题。 在listview 中加入CheckBox时,选中第一个,当往下滑动时,出现了下面没有选中的也被选中的情况,下面看看截图。
我在第一张图中选中了第一个和第二个CheckBox,将其后面的数量分别加到5和3,但是玩下滑动时,发现,在第7个和第8个item中,CheckBox也被选中,其后面的数量也和之前第一个和第二个一样。出现这种情况的原因就是我的listview在我的手机屏幕上只能加载6个item,在加载第一个时,会出现重复调用,后来我调整了listview的高度,将其调整为fill_parent 也是不行,后来在网上找到很多资料发现解决方法都太繁琐,我自己就写了一个简单的方法。
解决方法:
我的方法就是将CheckBox的选中状态保存起来,每次加载时,就会判断这个状态,这样就不会重复加载了。下面来看代码
先是Adapter的代码:
package com.example.book; import android.content.Context; import android.graphics.Color; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.CheckBox; import android.widget.CompoundButton; import android.widget.ImageView; import android.widget.TextView; import android.widget.Toast; import org.w3c.dom.Text; import java.util.List; /** * Created by THINK on 2017/10/28. */ public class MygouwuchebookAdapter extends ArrayAdapter{ private int resourseId; private Context context; private static boolean[] checks;//定义数组来保存CheckBox的状态 private String[] booknum;//同样定义数组来保存Textview的状态 private int length;//定义一个长度,来获取listview 的长度 public MygouwuchebookAdapter(Context context, int textViewResourseId, List objects) { super(context,textViewResourseId,objects); resourseId=textViewResourseId; this.context=context; checks = new boolean[objects.size()];//初始化数组 booknum=new String[objects.size()]; length=objects.size(); for(int i=0;i ; } } @Override public View getView(final int position, View converView, ViewGroup parent) { Mygouwuchebookclass mygouwuchebookclass=getItem(position); View view; final ViewHolder viewHolder; if(converView==null) { view = LayoutInflater.from(getContext()).inflate(resourseId, parent, false); viewHolder=new ViewHolder(); viewHolder.mygouwuchexuanze=(CheckBox) view.findViewById(R.id.Mygouwuchexuanze); viewHolder.mygouwuchebookimage=(ImageView)view.findViewById(R.id.mygouwuchebook); viewHolder.mygouwuchebookname=(TextView)view.findViewById(R.id.Mygouwuchebookname); viewHolder.mugouwuchebookprice=(TextView)view.findViewById(R.id.Mygouwuchebookprice); viewHolder.mygouwuchebooknum=(TextView)view.findViewById(R.id.Mygouwuchebooknum); viewHolder.mygouwuchebooknumjian=(Button)view.findViewById(R.id.Mygouwuchebooknumjian); viewHolder.mygouwuchebooknumjia=(Button)view.findViewById(R.id.Mygouwuchebooknumjia); viewHolder.mygouwuchebookshanchu=(Button)view.findViewById(R.id.Mygouwuchebookshanchu); view.setTag(viewHolder); } else { view=converView; viewHolder=(ViewHolder)view.getTag(); } final int pos = position;//定义一个final的int类型pos用来记录点击的位置 viewHolder.mygouwuchexuanze.setFocusable(false); viewHolder.mygouwuchebooknumjian.setFocusable(false); viewHolder.mygouwuchebooknumjia.setFocusable(false); viewHolder.mygouwuchebookshanchu.setFocusable(false); viewHolder.mygouwuchebooknumjian.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if(viewHolder.mygouwuchebooknum.getText().toString().equals("1")) { } else { viewHolder.mygouwuchebooknum.setText(String.valueOf(Integer.parseInt(viewHolder.mygouwuchebooknum.getText().toString())-1)); booknum[pos]=String.valueOf(Integer.parseInt(viewHolder.mygouwuchebooknum.getText().toString())); //text的text改变时,将text保存进数组里面 } } }); viewHolder.mygouwuchebooknumjia.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { viewHolder.mygouwuchebooknum.setText(String.valueOf(Integer.parseInt(viewHolder.mygouwuchebooknum.getText().toString())+1)); booknum[pos]=String.valueOf(Integer.parseInt(viewHolder.mygouwuchebooknum.getText().toString())); //text的text改变时,将text保存进数组里面 } }); viewHolder.mygouwuchebookshanchu.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Toast.makeText(context,position+"查看",Toast.LENGTH_LONG).show(); } }); viewHolder.mygouwuchebookimage.setImageResource(mygouwuchebookclass.getImageviewId()); viewHolder.mygouwuchebookname.setText(mygouwuchebookclass.getBookname()); viewHolder.mugouwuchebookprice.setText(String.valueOf(mygouwuchebookclass.getPrice())); //pos必须声明为final //下面是CheckBox的点击事件, viewHolder.mygouwuchexuanze.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){ @Override public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) { checks[pos] = isChecked;//当被选中时,将该位置的CheckBox的状态保存下来 }}); viewHolder.mygouwuchexuanze.setChecked(checks[pos]);//每次加载这个item时,将CheckBox的状态赋值就OK了 viewHolder.mygouwuchebooknum.setText(booknum[pos]);//每次加载item时,给TextView的text赋值就OK了 return view; } public static boolean[] getChecks() { return checks; } public static void setChecks(boolean[] checks) { MygouwuchebookAdapter.checks = checks; } /*public void quanxuan(boolean ischecked) { for(int i=0;i */ class ViewHolder { CheckBox mygouwuchexuanze; ImageView mygouwuchebookimage; TextView mygouwuchebookname; TextView mugouwuchebookprice; TextView mygouwuchebooknum; Button mygouwuchebooknumjian; Button mygouwuchebooknumjia; Button mygouwuchebookshanchu; CheckBox mygouwuchequanxuan; } }
下面是主活动:
package com.example.book; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.support.v7.widget.Toolbar; import android.text.Layout; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.CheckBox; import android.widget.CompoundButton; import android.widget.HorizontalScrollView; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.Toast; import java.util.ArrayList; import java.util.List; public class MygouwucheActivity extends AppCompatActivity { private ListmydianpubookclassList=new ArrayList<>(); private MygouwuchebookAdapter mygouwuchebookAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_mygouwuche); inits();//初始化list mygouwuchebookAdapter=new MygouwuchebookAdapter(MygouwucheActivity.this,R.layout.mygouwuchebook,mydianpubookclassList); ListView listView=(ListView)findViewById(R.id.mygouwuchelistview); listView.setAdapter(mygouwuchebookAdapter); listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView> parent, View view, final int position, long id) { Toast.makeText(MygouwucheActivity.this,position+"sss",Toast.LENGTH_LONG).show(); } }); /*CheckBox checkBoxquanxuan=(CheckBox)findViewById(R.id.mygouwuchecheckBox); checkBoxquanxuan.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){ @Override public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) { mygouwuchebookAdapter.quanxuan(isChecked); mygouwuchebookAdapter.notifyDataSetChanged(); }});*/ } } public void inits() { for (int i = 0; i < 3; i++) { Mygouwuchebookclass mygouwuchebookclass = new Mygouwuchebookclass(R.drawable.gonglue, "数据结构对对对点点滴滴", 3); mydianpubookclassList.add(mygouwuchebookclass); Mygouwuchebookclass mygouwuchebookclass1 = new Mygouwuchebookclass(R.drawable.fenlei, "数据结构对对对点点滴滴", 5); mydianpubookclassList.add(mygouwuchebookclass1); Mygouwuchebookclass mygouwuchebookclass2 = new Mygouwuchebookclass(R.drawable.fenlei, "数据结构对对对点点滴滴", 6); mydianpubookclassList.add(mygouwuchebookclass2); Mygouwuchebookclass mygouwuchebookclass3 = new Mygouwuchebookclass(R.drawable.shopping, "数据结构对对对点点滴滴", 2); mydianpubookclassList.add(mygouwuchebookclass3); Mygouwuchebookclass mygouwuchebookclass4 = new Mygouwuchebookclass(R.drawable.fenlei, "数据结构对对对点点滴滴", 8); mydianpubookclassList.add(mygouwuchebookclass4); Mygouwuchebookclass mygouwuchebookclass5 = new Mygouwuchebookclass(R.drawable.shopping, "数据结构对对对点点滴滴", 1); mydianpubookclassList.add(mygouwuchebookclass5); Mygouwuchebookclass mygouwuchebookclass6 = new Mygouwuchebookclass(R.drawable.gonglue, "数据结构对对对点点滴滴", 0); mydianpubookclassList.add(mygouwuchebookclass6); } } }
下面是主活动的布局文件:
xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/activity_mygouwuche" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.book.MygouwucheActivity"> <LinearLayout android:id="@+id/mygouwuchelayout" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_below="@+id/Mygouwuchetoolbar" android:layout_alignParentStart="true"> <ListView android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:layout_below="@+id/Mygouwuchetoolbar" android:layout_alignParentStart="true" android:id="@+id/mygouwuchelistview" /> LinearLayout> RelativeLayout>
listview的布局文件:
xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.book.MainActivity" android:background="#FFFFFFFF"> <LinearLayout android:orientation="horizontal" android:layout_width="match_parent" android:layout_marginTop="11dp" android:weightSum="1" android:layout_alignParentTop="true" android:layout_alignParentStart="true" android:layout_height="110dp"> <CheckBox android:layout_gravity="center" android:layout_height="match_parent" android:layout_marginLeft="15dp" android:layout_width="30dp" android:id="@+id/Mygouwuchexuanze" android:button="@drawable/checkboxseletor"/> <ImageView app:srcCompat="@color/colorPrimary" android:id="@+id/mygouwuchebook" android:layout_marginTop="10dp" android:layout_marginBottom="10dp" android:layout_marginLeft="15dp" android:layout_width="70dp" android:layout_height="90dp" /> <LinearLayout android:orientation="vertical" android:layout_height="110dp" android:layout_width="80dp"> <TextView android:text="TextView" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="10dp" android:layout_marginLeft="15dp" android:textSize="15sp" android:id="@+id/Mygouwuchebookname" /> <TextView android:text="TextView" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="20dp" android:layout_marginLeft="15dp" android:textSize="15sp" android:textColor="@android:color/holo_red_light" android:id="@+id/Mygouwuchebookprice" /> LinearLayout> <LinearLayout android:orientation="horizontal" android:layout_width="wrap_content" android:layout_weight="1" android:layout_height="110dp"> <Button android:text="-" android:textSize="40dp" android:layout_height="match_parent" android:id="@+id/Mygouwuchebooknumjian" android:layout_width="30dp" android:background="#FFFFFFFF" style="?android:attr/borderlessButtonStyle" android:textColor="#979696" /> <TextView android:layout_gravity="center" android:layout_marginLeft="5dp" android:textSize="25dp" android:text="1" android:layout_height="wrap_content" android:id="@+id/Mygouwuchebooknum" android:layout_width="30dp" android:textDirection="inherit" /> <Button android:text="+" android:textSize="30dp" android:layout_height="match_parent" android:id="@+id/Mygouwuchebooknumjia" android:layout_width="30dp" android:background="#FFFFFFFF" style="?android:attr/borderlessButtonStyle" android:textColor="#979696" /> <Button android:text="删除" android:layout_width="wrap_content" android:layout_height="match_parent" android:id="@+id/Mygouwuchebookshanchu" android:background="#FFFFFFFF" android:layout_weight="1" /> LinearLayout> LinearLayout> RelativeLayout>
加红色标记的为解决方案,我这里的listview是经过优化之后的,如果对listview优化不懂得可以先看看资料了解一下,看了我的代码是不是很简单就解决了这个问题呢?如果还有不懂得可以来问我。
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