ListView的运行效率与点击事件

提升ListView的运行效率

ListView的缓存原理

1、Adapter是ListView与数据之间的桥梁
2、ListView在开始绘制的时候，系统首先调用getCount（）方法，根据返回值得到ListView的长度，然后根据这个长度，调用getView（）一行一行地绘制ListView的每一项。
3、当ListView的每一项将要显示时，都会调用Adapter的getView（）方法返回一个View。
4、ListView中有多少项，就调用多少次getView（）方法去创建每一项的View，这一过程是耗时操作。

程序

public class MyListViewActivity extends AppCompatActivity {
private ListView mListView;
    private List<Student> mData;
     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_my_list_view);
   mListView= (ListView) findViewById(R.id.listview);
       initData();
        LayoutInflater inflater=getLayoutInflater();
        Studentadapter adapter=new Studentadapter(inflater,mData);
       mListView.setAdapter(adapter);
       }

    private void initData() {
        mData=new ArrayList<>();
        Student zhangsan=new Student("张三","20","男","吃",R.mipmap.uqiwei);
        Student lisi=new Student("李四","22","女","睡觉",R.mipmap.yangmi);
        Student wangwu=new Student("王五","25","男","打游戏",R.mipmap.ic_launcher);
        Student zhaoliu=new Student("赵六","23","女","逛街",R.mipmap.uqiwei);
        for(int i=0;i<50;i++) {
            mData.add(zhangsan);
            mData.add(lisi);
            mData.add(wangwu);
            mData.add(zhaoliu);
        }
    }
"****************************************************"
public class Studentadapter extends BaseAdapter {
    private List<Student> mData;
    private LayoutInflater mInflater;

    public Studentadapter(LayoutInflater inflater, List<Student> data) {
        mInflater = inflater;
        mData = data;
    }

    @Override
    public int getCount() {
        //得到ListView要显示数据的条数
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        //返回索引
        return position;
    }

    @Override
    public long getItemId(int position) {
        //返回索引
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //LayoutInflater
        Student student = mData.get(position);
        ViewHolder viewHolder = null;
        if (convertView == null) {
            viewHolder = new ViewHolder();
            convertView = mInflater.inflate(R.layout.simple_adapter, null);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageview_photo);
            viewHolder.textView_name = (TextView) convertView.findViewById(R.id.textview_name);
            viewHolder.textView_age = (TextView) convertView.findViewById(R.id.textview_age);
            viewHolder.textView_sex = (TextView) convertView.findViewById(R.id.textview_sex);
            viewHolder.textView_hobby = (TextView) convertView.findViewById(R.id.textview_hobby);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        viewHolder.textView_name.setText(student.getName());
        viewHolder.textView_age.setText(student.getAge());
        viewHolder.textView_hobby.setText(student.getHobby());
        viewHolder.textView_sex.setText(student.getSex());
        viewHolder.imageView.setImageResource(student.getImg());
        return convertView;
    }

    class ViewHolder {
        TextView textView_name;
        TextView textView_age;
        TextView textView_sex;
        TextView textView_hobby;
        ImageView imageView;
    }
}
"*******************************************"
<?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">

    <ImageView
        android:id="@+id/imageview_photo"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:src="@mipmap/yangmi"
        />
<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"

    android:layout_margin="20dp">
    <TextView
        android:id="@+id/textview_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="姓名"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
       >
        <TextView
            android:id="@+id/textview_age"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="年龄"/>
        <TextView
            android:id="@+id/textview_sex"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="性别"/>
    </LinearLayout>
    <TextView
        android:id="@+id/textview_hobby"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="爱好"/>

</LinearLayout>

</LinearLayout>
"********************************************************"
public class Student {
    private String name;
    private String hobby;
    private String  age;
    private String  sex;
    private int img;
    public Student(String name,String age,String sex,String hobby,int img){
        this.name=name;
        this.age=age;
        this.sex=sex;
        this.hobby=hobby;
        this.img=img;
    }

    public int getImg() {
      return img;
    }

    public void setImg(int img) {
        this.img = img;
    }



    public String getName() {
        return name;
    }

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

    public void setHobby(String hobby) {
        this.hobby = hobby;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }


    public String getSex() {
        return sex;
    }

    public String getHobby() {
        return hobby;
    }

    public String getAge() {
        return age;
    }
}

结果图：

ListView水果界面及各种效果图

ListView界面

<?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">

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

    </ListView>
</LinearLayout>

MyFruitActivity

public class MyFruitActivity extends AppCompatActivity {
private ListView mListView;
    private List<Fruit> mFruits;
    private Fruitadapter adapter;
    private  LayoutInflater Inflater;
    private  View mHeaderView;
    private Button mBtnCheckedAll;
    private  View mFooterView;
    private Button mBtnCheckedOver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_fruit);
        mListView= (ListView) findViewById(R.id.listview_fruit);
        Inflater=getLayoutInflater();
        initData();
        mFooterView=Inflater.inflate(R.layout.fruit_footer, null);
        mHeaderView=Inflater.inflate(R.layout.fruit_header,null);
        mBtnCheckedOver= (Button) mFooterView.findViewById(R.id.button_overChecked);

        mBtnCheckedAll= (Button) mHeaderView.findViewById(R.id.button_allChecked);
        mBtnCheckedOver.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                adapter.checkedOver();
            }
        });
       mBtnCheckedAll.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               //此处要全选
               adapter.checkedAll();
           }
       });
        mListView.addHeaderView(mHeaderView);
       mListView.addFooterView(mFooterView);
        adapter=new Fruitadapter(Inflater,mFruits);
        mListView.setAdapter(adapter);
        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Log.d("myfruit","点击的水果是："+mFruits.get(position-1).getName());
                adapter.itemSelect(position-1);
            }
        });
    }


    private void initData() {
  mFruits=new ArrayList<>();

        for(int i=0;i<50;i++) {
            Fruit apple=new Fruit("苹果",R.mipmap.pineapple);
            Fruit banana=new Fruit("香蕉",R.mipmap.fbanana);
            Fruit strawberry=new Fruit("葡萄",R.mipmap.fstrawberry);
            mFruits.add(apple);
            mFruits.add(banana);
            mFruits.add(strawberry);
        }
    }

全选和反选XML文件

<?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">
<Button
    android:id="@+id/button_allChecked"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="全选"/>
</LinearLayout>
"********************************************************"
<?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">
<Button
    android:id="@+id/button_overChecked"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="反选"/>
</LinearLayout>

水果布局XML文件

<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:gravity="center"
    android:orientation="horizontal"
    tools:context="com.example.administrator.mywiget.MyFruitActivity">
 <CheckBox
        android:id="@+id/checkbox_choose"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:focusable="false"
        android:text="选择水果"/>
    <ImageView
        android:id="@+id/imageview_fruit"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:src="@mipmap/peach"/>
    <TextView
        android:id="@+id/textview_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="苹果"
        />

</LinearLayout>

布局视图：

Fruit类

public class Fruit {
    private String name;
    private int Img;
    private boolean isChecked;

    public boolean isChecked() {
        return isChecked;
    }

    public void setIsChecked(boolean isChecked) {
        this.isChecked = isChecked;
    }

    public String getName() {
        return name;
    }

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

    public int getImg() {
        return Img;
    }

    public void setImg(int img) {
        Img = img;
    }

    public Fruit(String name, int img) {
        this.name = name;
        Img = img;
    }
}

Fruitadapter适配器

public class Fruitadapter extends BaseAdapter {
    private List<Fruit> mFruits;
    private LayoutInflater mInflater;
    private boolean[] mManagerAllCheckBox;

    public Fruitadapter(LayoutInflater Inflater, List<Fruit> Fruits) {
        mInflater = Inflater;
        mFruits = Fruits;
        //有多少条数据就有多少个checkBox
        mManagerAllCheckBox = new boolean[Fruits.size()];
    }

    /** * 全部选择 */
    public void checkedAll(){
        for(int i=0;i<mManagerAllCheckBox.length;i++){
            mManagerAllCheckBox[i]=true;
        }
        notifyDataSetChanged();
    }

    public void checkedOver(){
        for (int i=0;i<mManagerAllCheckBox.length;i++){
            mManagerAllCheckBox[i]=!mManagerAllCheckBox[i];
        }
        notifyDataSetChanged();
    }
    public void itemSelect(int position) {
        mManagerAllCheckBox[position] = !mManagerAllCheckBox[position];
        notifyDataSetChanged();
    }

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

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

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

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.activity_my_fruit, null);
            viewHolder = new ViewHolder();
            viewHolder.checkBox = (CheckBox) convertView.findViewById(R.id.checkbox_choose);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageview_fruit);
            viewHolder.textView = (TextView) convertView.findViewById(R.id.textview_name);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        Fruit fruit = mFruits.get(position);
        viewHolder.imageView.setImageResource(fruit.getImg());
        viewHolder.textView.setText(fruit.getName());
        viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                Log.d("myFruit", "选择框发生的变化：" + isChecked);
                mManagerAllCheckBox[position] = isChecked;
                notifyDataSetChanged();
            }
        });
        viewHolder.checkBox.setChecked(mManagerAllCheckBox[position]);
        return convertView;
    }

    class ViewHolder {
        CheckBox checkBox;
        ImageView imageView;
        TextView textView;
    }
}

结果图