Android学习（ListView）

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本文详细介绍如何自定义BaseAdapter并结合ListView展示复杂数据。包括实体类创建、Adapter继承、ViewHolder模式应用、多布局实现及数据更新技巧。此外，还探讨了ListView的高级特性如表头表尾设置、焦点管理等。

自定义BaseAdapter，然后绑定ListView的最简单例子
在这里插入图片描述
Animal.java:

public class Animal {
    private String aName;
    private String aSpeak;
    private int aIcon;

    public Animal() {
    }

    public Animal(String aName, String aSpeak, int aIcon) {
        this.aName = aName;
        this.aSpeak = aSpeak;
        this.aIcon = aIcon;
    }

    public String getaName() {
        return aName;
    }

    public String getaSpeak() {
        return aSpeak;
    }

    public int getaIcon() {
        return aIcon;
    }

    public void setaName(String aName) {
        this.aName = aName;
    }

    public void setaSpeak(String aSpeak) {
        this.aSpeak = aSpeak;
    }

    public void setaIcon(int aIcon) {
        this.aIcon = aIcon;
    }
}

AnimalAdapter.java：

public class AnimalAdapter extends BaseAdapter {

    private LinkedList<Animal> mData;
    private Context mContext;

    public AnimalAdapter(LinkedList<Animal> mData, Context mContext) {
        this.mData = mData;
        this.mContext = mContext;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
	    ViewHolder holder = null;
	    if(convertView == null){
	        convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list_animal,parent,false);
	        holder = new ViewHolder();
	        holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
	        holder.txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
	        holder.txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
	        convertView.setTag(holder);   //将Holder存储到convertView中
	    }else{
	        holder = (ViewHolder) convertView.getTag();
	    }
	    holder.img_icon.setBackgroundResource(mData.get(position).getaIcon());
	    holder.txt_aName.setText(mData.get(position).getaName());
	    holder.txt_aSpeak.setText(mData.get(position).getaSpeak());
	    return convertView;
	}
	
	static class ViewHolder{
	    ImageView img_icon;
	    TextView txt_aName;
	    TextView txt_aSpeak;
	}
}

MainActivity.java：

public class MainActivity extends AppCompatActivity {

    private List<Animal> mData = null;
    private Context mContext;
    private AnimalAdapter mAdapter = null;
    private ListView list_animal;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = MainActivity.this;
        list_animal = (ListView) findViewById(R.id.list_animal);
        mData = new LinkedList<Animal>();
        mData.add(new Animal("狗说", "你是狗么?", R.mipmap.ic_icon_dog));
        mData.add(new Animal("牛说", "你是牛么?", R.mipmap.ic_icon_cow));
        mData.add(new Animal("鸭说", "你是鸭么?", R.mipmap.ic_icon_duck));
        mData.add(new Animal("鱼说", "你是鱼么?", R.mipmap.ic_icon_fish));
        mData.add(new Animal("马说", "你是马么?", R.mipmap.ic_icon_horse));
        mAdapter = new AnimalAdapter((LinkedList<Animal>) mData, mContext);
        list_animal.setAdapter(mAdapter);
    }

}

表头表尾分割线的设置：

ooterDividersEnabled：是否在footerView(表尾)前绘制一个分隔条,默认为true
headerDividersEnabled:是否在headerView(表尾)前绘制一个分隔条,默认为true
divider:设置分隔条,可以用颜色分割,也可以用drawable资源分割
dividerHeight:设置分隔条的高度

翻遍了了API发现并没有可以直接设置ListView表头或者表尾的属性，只能在Java中写代码进行设置了，可供我们调用的方法如下：

addHeaderView(View v)：添加headView(表头),括号中的参数是一个View对象
使用这个addHeaderView方法必须放在listview.setAdapter前面，否则会报错
addFooterView(View v)：添加footerView(表尾)，括号中的参数是一个View对象
addHeaderView(headView, null, false)：和前面的区别：设置Header是否可以被选中
addFooterView(View,view,false)：同上

//添加表头和表尾需要写在setAdapter方法调用之前！！！
        list_animal.addHeaderView(headView);
        list_animal.addFooterView(footView);

        list_animal.setAdapter(mAdapter);
        list_animal.setOnItemClickListener(this);

列表从底部开始显示：stackFromBottom
将stackFromBottom 属性设置为true即可

设置点击颜色cacheColorHint
如果你为ListView设置了一个图片作为Background的话，当你拖动或者点击listView空白位置会发现 item都变成黑色了，这是时候我们可以通过这个cacheColorHint将颜色设置为透明:#00000000

隐藏滑动条
可以通过设置：android:scrollbars=“none” 或者 setVerticalScrollBarEnabled(true); 解决这个问题

ListView的焦点问题

方法1：为抢占了控件的组件设置:android:focusable=“false”
为抢占了ListView Item焦点的控件设置android:focusable="false"即可解决这个问题或者在代码中获得控件后调用：setFocusable(false)

方法2：item根节点设置android:descendantFocusability=“blocksDescendants”
在Item布局的根节点添加上述属性，android:descendantFocusability=“blocksDescendants” 即可，另外该属性有三个可供选择的值：

beforeDescendants：viewgroup会优先其子类控件而获取到焦点
afterDescendants：viewgroup只有当其子类控件不需要获取焦点时才获取焦点
blocksDescendants：viewgroup会覆盖子类控件而直接获得焦点

ListView之checkbox错位问题解决

Entity类：Person.java：

public class Person implements Serializable{
    private String name;
    private String number;
    private boolean checkStatus;
    
    public Person(String name, String number) {
        super();
        this.name = name;
        this.number = number;
        this.checkStatus = false;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public boolean getCheckStatus() {
        return checkStatus;
    }

    public void setCheckStatus(boolean checkStatus) {
        this.checkStatus = checkStatus;
    }
    
}

实现的Adapter类：ContactListAdapter.java：

public class ContactListAdapter extends BaseAdapter implements CompoundButton.OnCheckedChangeListener{

    private List<Person> mData;
    private Context mContext;

    public ContactListAdapter(List<Person> data, Context context) {
        mData = data;
        mContext = context;
    }

    // 定义一个刷新数据的方法
    public void changeData(List<Person> data) {
        mData = data;
        notifyDataSetChanged();
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Person getItem(int position) {
        return mData.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final int index = position;
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(
                    R.layout.item_contact, parent, false);
            viewHolder = new ViewHolder();
            viewHolder.ly = (RelativeLayout) convertView
                    .findViewById(R.id.lyContactListItem);
            viewHolder.txtName = (TextView) convertView
                    .findViewById(R.id.txtName);
            viewHolder.txtNumber = (TextView) convertView
                    .findViewById(R.id.txtNumber);
            viewHolder.cbxStatus = (CheckBox) convertView
                    .findViewById(R.id.cbxStatus);
            convertView.setTag(viewHolder);
            viewHolder.cbxStatus.setTag(index);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        viewHolder.cbxStatus.setOnCheckedChangeListener(this);
        viewHolder.cbxStatus.setChecked(mData.get(position).getcheckStatus());
        viewHolder.txtName.setText(mData.get(index).getName());
        viewHolder.txtNumber.setText(mData.get(index).getNumber());
        return convertView;
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        int index = (int)buttonView.getTag();
        if (isChecked)
            mData.get(index).setCheckStatus(true);
        else
            mData.get(index).setCheckStatus(false);
    }


    private class ViewHolder {
        RelativeLayout ly;
        TextView txtName;
        TextView txtNumber;
        CheckBox cbxStatus;
    }
}

checkbox监听器的方法要添加在初始化Checkbox状态的代码之前

ListView的数据更新问题

entity类：Data.java：

public class Data {
    private int imgId;
    private String content;

    public Data() {}

    public Data(int imgId, String content) {
        this.imgId = imgId;
        this.content = content;
    }

    public int getImgId() {
        return imgId;
    }

    public String getContent() {
        return content;
    }

    public void setImgId(int imgId) {
        this.imgId = imgId;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

activity_main.xml：

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

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="添加一条记录" />

        <Button
            android:id="@+id/btn_add2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="往第五列插入一条数据" />


    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_remove"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="根据对象删除数据" />

        <Button
            android:id="@+id/btn_remove2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="根据游标删除数据" />


    </LinearLayout>


    <ListView
        android:id="@+id/list_one"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/txt_empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textColor="#000000"
        android:textSize="15pt" />

</LinearLayout>

item_list.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">

    <ImageView
        android:id="@+id/img_icon"
        android:layout_width="56dp"
        android:layout_height="56dp"/>

    <TextView
        android:id="@+id/txt_content"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:layout_marginLeft="10dp"
        android:textSize="18sp" />

</LinearLayout>

自定义BaseAdapter的实现：MyAdapter.java：

public class MyAdapter extends BaseAdapter {

    private Context mContext;
    private LinkedList<Data> mData;

    public MyAdapter() {
    }

    public MyAdapter(LinkedList<Data> mData, Context mContext) {
        this.mData = mData;
        this.mContext = mContext;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list, parent, false);
            holder = new ViewHolder();
            holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
            holder.txt_content = (TextView) convertView.findViewById(R.id.txt_content);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.img_icon.setImageResource(mData.get(position).getImgId());
        holder.txt_content.setText(mData.get(position).getContent());
        return convertView;
    }

    //添加一个元素
    public void add(Data data) {
        if (mData == null) {
            mData = new LinkedList<>();
        }
        mData.add(data);
        notifyDataSetChanged();
    }

    //往特定位置，添加一个元素
    public void add(int position,Data data){
        if (mData == null) {
            mData = new LinkedList<>();
        }
        mData.add(position, data);
        notifyDataSetChanged();
    }

    public void remove(Data data) {
        if(mData != null) {
            mData.remove(data);
        }
        notifyDataSetChanged();
    }

    public void remove(int position) {
        if(mData != null) {
            mData.remove(position);
        }
        notifyDataSetChanged();
    }

    public void clear() {
        if(mData != null) {
            mData.clear();
        }
        notifyDataSetChanged();
    }





    private class ViewHolder {
        ImageView img_icon;
        TextView txt_content;
    }

}

MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private ListView list_one;
    private TextView txt_empty;
    private Button btn_add;
    private Button btn_add2;
    private Button btn_remove;
    private Button btn_remove2;
    private MyAdapter mAdapter = null;
    private List<Data> mData = null;
    private Context mContext = null;
    private int flag = 1;
    private Data mData_5 = null;   //用来临时放对象的

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = MainActivity.this;
        mData = new LinkedList<Data>();
        mAdapter = new MyAdapter((LinkedList<Data>) mData,mContext);
        bindViews();

    }

    private void bindViews(){

        list_one = (ListView) findViewById(R.id.list_one);
        txt_empty = (TextView) findViewById(R.id.txt_empty);
        btn_add = (Button) findViewById(R.id.btn_add);
        btn_add2 = (Button) findViewById(R.id.btn_add2);
        btn_remove = (Button) findViewById(R.id.btn_remove);
        btn_remove2 = (Button) findViewById(R.id.btn_remove2);

        txt_empty.setText("暂无数据~");
        list_one.setAdapter(mAdapter);
        list_one.setEmptyView(txt_empty);
        btn_add.setOnClickListener(this);
        btn_add2.setOnClickListener(this);
        btn_remove.setOnClickListener(this);
        btn_remove2.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_add:
                if(flag == 5){
                    mData_5 = new Data(R.mipmap.ic_icon_qitao,"给猪哥跪了~~~ x " + flag);
                    mAdapter.add(mData_5);
                }else{
                    mAdapter.add(new Data(R.mipmap.ic_icon_qitao,"给猪哥跪了~~~ x " + flag));
                }
                flag++;
                break;
            case R.id.btn_add2:
                //position从0开始算的
                mAdapter.add(4,new Data(R.mipmap.ic_icon_qitao,"给猪哥跪了~~~ x " + flag));
                break;
            case R.id.btn_remove:
                mAdapter.remove(mData_5);
                break;
            case R.id.btn_remove2:
                mAdapter.remove(2);
                break;
        }
    }
}

ListView Item多布局的实现

MutiLayoutAdapter.java

public class MutiLayoutAdapter extends BaseAdapter{

    //定义两个类别标志
    private static final int TYPE_BOOK = 0;
    private static final int TYPE_APP = 1;
    private Context mContext;
    private ArrayList<Object> mData = null;


    public MutiLayoutAdapter(Context mContext,ArrayList<Object> mData) {
        this.mContext = mContext;
        this.mData = mData;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return mData.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    //多布局的核心，通过这个判断类别
    @Override
    public int getItemViewType(int position) {
        if (mData.get(position) instanceof App) {
            return TYPE_APP;
        } else if (mData.get(position) instanceof Book) {
            return TYPE_BOOK;
        } else {
            return super.getItemViewType(position);
        }
    }

    //类别数目
    @Override
    public int getViewTypeCount() {
        return 2;
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        int type = getItemViewType(position);
        ViewHolder1 holder1 = null;
        ViewHolder2 holder2 = null;
        if(convertView == null){
           switch (type){
               case TYPE_APP:
                   holder1 = new ViewHolder1();
                   convertView = LayoutInflater.from(mContext).inflate(R.layout.item_one, parent, false);
                   holder1.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
                   holder1.txt_aname = (TextView) convertView.findViewById(R.id.txt_aname);
                   convertView.setTag(R.id.Tag_APP,holder1);
                   break;
               case TYPE_BOOK:
                   holder2 = new ViewHolder2();
                   convertView = LayoutInflater.from(mContext).inflate(R.layout.item_two, parent, false);
                   holder2.txt_bname = (TextView) convertView.findViewById(R.id.txt_bname);
                   holder2.txt_bauthor = (TextView) convertView.findViewById(R.id.txt_bauthor);
                   convertView.setTag(R.id.Tag_Book,holder2);
                   break;
           }
        }else{
            switch (type){
                case TYPE_APP:
                    holder1 = (ViewHolder1) convertView.getTag(R.id.Tag_APP);
                    break;
                case TYPE_BOOK:
                    holder2 = (ViewHolder2) convertView.getTag(R.id.Tag_Book);
                    break;
            }
        }

        Object obj = mData.get(position);
        //设置下控件的值
        switch (type){
            case TYPE_APP:
                App app = (App) obj;
                if(app != null){
                    holder1.img_icon.setImageResource(app.getaIcon());
                    holder1.txt_aname.setText(app.getaName());
                }
                break;
            case TYPE_BOOK:
                Book book = (Book) obj;
                if(book != null){
                    holder2.txt_bname.setText(book.getbName());
                    holder2.txt_bauthor.setText(book.getbAuthor());
                }
                break;
        }
        return convertView;
    }


    //两个不同的ViewHolder
    private static class ViewHolder1{
        ImageView img_icon;
        TextView txt_aname;
    }

    private static class ViewHolder2{
        TextView txt_bname;
        TextView txt_bauthor;
    }
}

这里有个地方要注意的，convertView.setTag(R.id.Tag_APP,holder1);我们平时都直接 setTag(Object)的，这个是setTag的重载方法，参数是一个唯一的key以及后面的一个对象

strings.xml

<resources>
    <string name="app_name">ListViewDemo6</string>

    <string name="hello_world">Hello world!</string>
    <string name="action_settings">Settings</string>


    <item name="Tag_APP" type="id"></item>
    <item name="Tag_Book" type="id"></item>

</resources>

MainActivity.java：

public class MainActivity extends AppCompatActivity {

    private static final int TYPE_BOOK = 0;
    private static final int TYPE_APP = 1;
    private ListView list_content;
    private ArrayList<Object> mData = null;
    private MutiLayoutAdapter myAdapter = null;

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

        //数据准备：
        mData = new ArrayList<Object>();
        for(int i = 0;i < 20;i++){
            switch ((int)(Math.random() * 2)){
                case TYPE_BOOK:
                    mData.add(new Book("《第一行代码》","郭霖"));
                    break;
                case TYPE_APP:
                    mData.add(new App(R.mipmap.iv_icon_baidu,"百度"));
                    break;
            }
        }

        list_content = (ListView) findViewById(R.id.list_content);
        myAdapter = new MutiLayoutAdapter(MainActivity.this,mData);
        list_content.setAdapter(myAdapter);
    }
}

App.java

public class App {
    private int aIcon;
    private String aName;

    public App() {
    }

    public App(int aIcon, String aName) {
        this.aIcon = aIcon;
        this.aName = aName;
    }

    public int getaIcon() {
        return aIcon;
    }

    public String getaName() {
        return aName;
    }

    public void setaIcon(int aIcon) {
        this.aIcon = aIcon;
    }

    public void setaName(String aName) {
        this.aName = aName;
    }
}

item_one.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:padding="5dp">

    <ImageView
        android:id="@+id/img_icon"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@mipmap/iv_icon_baidu" />

    <TextView
        android:id="@+id/txt_aname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginTop="20dp"
        android:text="百度"
        android:textSize="20sp" />


</LinearLayout>

Book.java

public class Book {
    private String bName;
    private String bAuthor;

    public Book() {
    }

    public Book(String bName, String bAuthor) {
        this.bName = bName;
        this.bAuthor = bAuthor;
    }

    public String getbName() {
        return bName;
    }

    public String getbAuthor() {
        return bAuthor;
    }

    public void setbName(String bName) {
        this.bName = bName;
    }

    public void setbAuthor(String bAuthor) {
        this.bAuthor = bAuthor;
    }
}

item_two.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:padding="10dp">

    <TextView
        android:id="@+id/txt_bname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="一条数据"
        android:textColor="#F3684A"
        android:textSize="18sp" />

    <TextView
        android:id="@+id/txt_bauthor"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:text="小明"
        android:textColor="#44BDED"
        android:textSize="18sp" />

</LinearLayout>