工具类/基础优化形ListView

创建类继承自arrayAdapter类->重写父类方法->建立自定义ViewHolder->将数据类中的数据实例化->用ViewHolder存储于View中->setTag（）设置数据

使用ViewHolder模式提高效率

    ViewHolder利用listView的试图缓存机制，每次getView（），通过findViewById（）实例化控件。

    当数量较多，频繁动态增减时使用arrayadapter，通过setNotifyOnChange，降低view的处理量。

convertView：用于将之前加载好的布局进行缓存，以便以后可以进行重用。

resourceId=textViewResourceId->ListView子项布局id

if (cOnvertView==null){
    view=LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
    viewHolder=new ViewHolder();
    viewHolder.imageView= (ImageView) view.findViewById(R.id.imageView);
    viewHolder.textView= (TextView) view.findViewById(R.id.textView);

如果convertView为null，使用LayoutInflater加载布局

 view=LayoutInflater.from(getContext()).inflate(resourceId,parent,false);

package com.example.yrc.listviewptest;

import android.content.Context;
import android.support.annotation.IdRes;
import android.support.annotation.LayoutRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

/**  * Created by YRC on 2017/5/29.  */  public class ViewHolderAdapter extends ArrayAdapter {
    private int resourceId;


    public ViewHolderAdapter(Context context,int textViewResourceId,List objects) {
        super(context, textViewResourceId, objects);
        resourceId=textViewResourceId;
    }

    @NonNull
    @Override
    public View getView(int position,  View convertView,  ViewGroup parent) {
        Form form=getItem(position);
        View view;
        ViewHolder viewHolder;
        if (cOnvertView==null){
            view=LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
            viewHolder=new ViewHolder();
            viewHolder.imageView= (ImageView) view.findViewById(R.id.imageView);
            viewHolder.textView= (TextView) view.findViewById(R.id.textView);
            view.setTag(viewHolder);
        }else {
            view=convertView;
            viewHolder= (ViewHolder) view.getTag();
        }
        viewHolder.imageView.setImageResource(form.getImageId());
        viewHolder.textView.setText(String.valueOf(form.getNumber()));
        return view;
    }

    class ViewHolder{
        ImageView imageView;
        TextView textView;
    }
}

MainActivity

public class MainActivity extends AppCompatActivity {
    private List formList=new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initForm();
        final ViewHolderAdapter adapter=new ViewHolderAdapter(MainActivity.this,
                                                        R.layout.viewholder_item,formList);
        Button button= (Button) findViewById(R.id.b1);
        final ListView listView= (ListView) findViewById(R.id.ListView);
        listView.setAdapter(adapter);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Form form18=new Form(9,R.mipmap.ic_launcher);
                formList.add(form18);
                adapter.notifyDataSetChanged();
                listView.setSelection(formList.size()-1);
            }
        });
        for (int i=0;iprivate void initForm() {
        Form form1=new Form(1,R.mipmap.ic_launcher);
        formList.add(form1);
        Form form2=new Form(2,R.mipmap.ic_launcher);
        formList.add(form2);
        Form form3=new Form(3,R.mipmap.ic_launcher);
        formList.add(form3);
        Form form4=new Form(4,R.mipmap.ic_launcher);
        formList.add(form4);
        Form form5=new Form(5,R.mipmap.ic_launcher);
        formList.add(form5);
        Form form6=new Form(6,R.mipmap.ic_launcher);
        formList.add(form6);
        Form form7=new Form(7,R.mipmap.ic_launcher);
        formList.add(form7);
    }
}

写在最后 

设置分隔线：android：divider=“@android:color:”

                                        divider

                                        divider="@null"  透明

隐藏滚动条：android：scrollbars="none"

设置ListView显示在第几项 listView.setSelection(N)    

                                          listView.smoothScrollBy()

                                          listView.smoothScrollByOffset

                                          listView.smoothScrollToPosition

取消Item点击效果：android:listSelector="#00000000"

动态修改ListView :修改传递给Adapter映射的List    add（）

                              调用notifyDataSetChanged()进行动态修改

遍历ListView所有的子成员： 

for (int i=0;i 
 
处理空ListView ：Listview.setEmptyView