封装适配器

先看效果：

具体实现：

1.CommonAdapter：

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

public abstract class CommonAdapter<T> extends BaseAdapter {
    private Context context;
    private List<T> list;
    private LayoutInflater inflater;
    private int itemLayoutId;

    public CommonAdapter(Context context, List<T> list, int itemLayoutId) {
        this.context = context;
        this.list = list;
        this.itemLayoutId = itemLayoutId;
        inflater = LayoutInflater.from(context);
    }

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

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

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        CommonViewHolder holder = getViewHolder(position, convertView, parent);
        convert(holder, (T) getItem(position));
        return holder.getConvertView();
    }

    public abstract void convert(CommonViewHolder holder, T item);

    private CommonViewHolder getViewHolder(int position, View convertView, ViewGroup parent) {
        return CommonViewHolder.get(context, convertView, parent, itemLayoutId, position);
    }
}

2.commonViewHolder:
 
import android.content.Context;
import android.graphics.Bitmap;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.bumptech.glide.Glide;

public class CommonViewHolder {
    //现在对于int作为键的官方推荐用SparseArray替代HashMap
    private final SparseArray<View> views;
    private View convertView;
    private Context context;

    private CommonViewHolder(Context context, ViewGroup parent, int layoutId, int position) {
        this.context = context;
        this.views = new SparseArray<>();
        this.convertView = LayoutInflater.from(parent.getContext()).inflate(layoutId, parent, false);
        convertView.setTag(this);
    }

    /**
     * 拿到一个ViewHolder对象
     */
    public static CommonViewHolder get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {
        if (convertView == null) {
            return new CommonViewHolder(parent.getContext(), parent, layoutId, position);
        }
        return (CommonViewHolder) convertView.getTag();
    }

    /**
     * 通过控件的Id获取对于的控件，如果没有则加入views
     */
    public <T extends View> T getView(int viewId) {
        View view = views.get(viewId);
        if (view == null) {
            view = convertView.findViewById(viewId);
            views.put(viewId, view);
        }
        return (T) view;
    }

    public View getConvertView() {
        return convertView;
    }

    //设置字符串
    public CommonViewHolder setText(int viewId, String text) {
        TextView tv = getView(viewId);
        tv.setText(text);
        return this;
    }

    //设置图片
    public CommonViewHolder setImageByUrl(int viewId, String url) {
        Glide.with(context).load(url).into((ImageView) getView(viewId));
        return this;
    }

    public CommonViewHolder setImageResource(int viewId, int drawableId) {
        ImageView iv = getView(viewId);
        iv.setImageResource(drawableId);
        return this;
    }

    public CommonViewHolder setImageBitmap(int viewId, Bitmap bitmap) {
        ImageView iv = getView(viewId);
        iv.setImageBitmap(bitmap);
        return this;
    }
}

3.MyData:

public class MyData {
    private String name;

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

    public String getName() {
        return name;
    }

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

4.MainActivity:

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView mListView;

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

    }

    private void initData() {
        final List<MyData> list = new ArrayList<>();
        for (int i = 0; i < 50; i++) {
            list.add(new MyData("刘婕" + i + ""));
        }
        mListView.setAdapter(new CommonAdapter<MyData>(this, list, R.layout.item) {
            @Override
            public void convert(CommonViewHolder holder, MyData item) {
                holder.setText(R.id.text, item.getName());
                holder.setImageResource(R.id.image,R.mipmap.ic_launcher);
            }
        });
    }

    private void initView() {
        mListView = (ListView) findViewById(R.id.listView);
    }
}

5.activity_main:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.administrator.commonadapter.MainActivity">

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

</android.support.constraint.ConstraintLayout>

6.item:

<?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">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp" />

    <ImageView
        android:id="@+id/image"
        android:layout_width="30dp"
        android:layout_height="20dp" />
</LinearLayout>

这就封装好了。