BaseAdapter简单封装

一、前言

在Android开发中，常常需要使用到适配器，但是每次都直接继承BaseAdapter造成了很多重复的代码和逻辑，因此我们可以对BaseAdapter进行一次封装，大大减少我们的重复代码和逻辑

二、使用

这里介绍一个我在开发中使用的一个BaseAdapter的封装，它的优势有：

代码简单，只有不到100行的代码
效率高，内部已完成ViewHolder的重用，静态的ViewHolder内部类更节约资源，加载速度更快，并用更高效的SparseArray存储View
使用简单，使用如下

public class TestAdapter extends MyBaseAdapter<Person> {

private ImageView image;
private TextView name;

/**
* @param list 数据
* @param layout 布局id
*/
public TestAdapter(Context context, List<Person> list, int layout) {
super(context, list, layout);
}

@Override
public void convert(ViewHolder holder, Person person) {
image = holder.findViewById(R.id.image);
name = holder.findViewById(R.id.name);
image.setImageResource(R.mipmap.ic_launcher);
name.setText(person.getName());
}
}

我们只需要继承MyBaseAdapter，并重写必要的构造方法和抽象方法即可。其中Person类为一个bean类。

三、效果图

四、MyBaseAdapter及其它类

MyBaseAdapter类

package com.afei.baseadapterdemo.adapter;

import java.util.List;

import android.content.Context;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

public abstract class MyBaseAdapter<T> extends BaseAdapter {
protected Context mContext;
protected List<T> mList; // 数据
protected int mLayout; // 布局id

public MyBaseAdapter(Context context, List<T> list, int layout) {
this.mContext = context;
this.mList = list;
this.mLayout = layout;
}

@Override
public int getCount() {
return mList == null ? 0 : mList.size();
}

@Override
public Object getItem(int position) {
return mList == null ? null : mList.get(position);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = ViewHolder.getInstance(mContext, convertView, mLayout);
convert(holder, mList.get(position)); // 子类重写的方法，完成holder中view的初始化
return holder.getConvertView();
}

/**
* 子类必须重写的方法，通过这个方法初始化holder中的View即可
*/
public abstract void convert(ViewHolder holder, T t);

protected static class ViewHolder {
private View convertView;
private SparseArray<View> views;

private ViewHolder(View convertView) {
this.views = new SparseArray<View>();
this.convertView = convertView;
convertView.setTag(this);
}

public static ViewHolder getInstance(Context context, View convertView, int layout) {
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(layout, null);
return new ViewHolder(convertView);
}
return (ViewHolder) convertView.getTag(); // 重用convertView
}

@SuppressWarnings("unchecked")
public <T extends View> T findViewById(int id) {
View view = views.get(id); // 同id的控件可重复使用，无需再次findViewById
if (view == null) {
view = convertView.findViewById(id);
views.append(id, view); // 将此id的控件添加进sparseArray
}
return (T) view;
}

private View getConvertView() {
return convertView;
}
}
}

Person类

public class Person {

private String name;

public Person(String name) {
this.name = name;
}

public String getName() {
return name;
}

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

MainActivity

package com.afei.baseadapterdemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;

import com.afei.baseadapterdemo.adapter.TestAdapter;
import com.afei.baseadapterdemo.bean.Person;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

private ListView mListView;

private TestAdapter mAdapter;
private ArrayList<Person> mList;

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

private void initView() {
mListView = (ListView) findViewById(R.id.listView);
mList = new ArrayList<>();
for (int i = 0; i < 20; i++) {
mList.add(new Person("美女" + i));
}
mAdapter = new TestAdapter(this, mList, R.layout.item_list);
mListView.setAdapter(mAdapter);
}
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
tools:context="com.afei.baseadapterdemo.MainActivity">

<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>

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"
android:gravity="center_vertical"
android:padding="20dp">

<ImageView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"/>

</LinearLayout>