ListView和RecyclerView的使用和效能優化總結
阿新 • • 發佈：2019-01-09
1.ListView介紹
在手機中，使用列表顯示是一種常見的顯示格式，那麼ListView就是一種常見的方式。例如：今日頭條，網易新聞都是使用ListView或者是最近流行的RecyclerView進行首頁的佈局，最後一節將會對它進行介紹。
2.ListView常用方法和實現邏輯介紹
2.1使用ListView
Android提供了ListView和ExpandableListView用來實現ListView這個功能。2.2 Adapter介面卡
當你需要建立一個ListView時，需要繫結一個adapter用來實現listview中的item view資源申請和item view的資料繫結。2.3 ListView的過濾和排序
ListView也可以實現對每一個item進行過濾或者排序，當然在開發的工程中也需要對adapter進行設計才能實現該項功能。2.4 動態更新
notifyDataSetChanged()：這個方法將在資料被改變，或者資料新建立的時候會被呼叫。這個時候你可以在這個方法中重寫方
法以至於達到動態更新資料的目的。
3.預設介面卡
3.1 預設平臺介面卡
Android提供了預設的介面卡，最主要的兩個是：ArrayAdapter和CursorAdapter。其中ArrayAdapter可基於Arrays
或java.util.List來處理資料。而SimpleCursorAdapter可以處理相關資料庫。
3.2使用ArrayAdapter的一個例子：
package com.example.zhengxie.demo_testcase;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.ListView;
import android.widget.TextView;
import java.security.KeyStore;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class MainActivity extends AppCompatActivity {
ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listview);
String[] values = new String[]{"中國移動", "中國聯通", "中國電信"};
final ArrayList<String> arrayList = new ArrayList<String>();
for (int i = 0; i < values.length; i++) {
arrayList.add(values[i]);
}
//設定adapter(context,listview中的樣式，資料)
final StableArrayAdapter adapter = new StableArrayAdapter(this, R.layout.rowbuttonlayout, arrayList);
listView.setAdapter(adapter);
//當用戶點選了一個Item時，對Item的監聽事件
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, final View view, int position, long id) {
final String item = (String) parent.getItemAtPosition(position);
view.animate().setDuration(2000).alpha(0).withEndAction(new Runnable() {//對view的漸變顯示
@Override
public void run() {
arrayList.remove(item);
adapter.notifyDataSetChanged();//記：View refresh
view.setAlpha(1);//0為透明，1為不透明
}
});
}
});
}
private class StableArrayAdapter extends ArrayAdapter<String> {
HashMap<String, Integer> mInMap = new HashMap<String, Integer>();
private Context context;
private List<String> list;
public StableArrayAdapter(Context context, int resource, List<String> objects) {
super(context, resource, objects);
this.context = context;
this.list = objects;
for (int i = 0; i < objects.size(); i++) {
mInMap.put(objects.get(i), i);
}
}
@Override
public long getItemId(int position) {
String item = getItem(position);
return mInMap.get(item);
}
@Override
public boolean hasStableIds() {
return true;
}
@NonNull
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.rowbuttonlayout,null);
final ViewHolder viewHolder ;
if (convertView == null){//佈局快取是否為空
viewHolder = new ViewHolder();
viewHolder.textView = (TextView) view.findViewById(R.id.label);
viewHolder.checkBox = (CheckBox) view.findViewById(R.id.check);
viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
viewHolder.checkBox.setSelected(buttonView.isChecked());
}
});
view.setTag(viewHolder);//將viewHolder載入到view中
}
else {
view = convertView;
viewHolder = (ViewHolder) view.getTag();
}
viewHolder.textView.setText(list.get(position));
viewHolder.checkBox.setSelected(false);
return view;
}
class ViewHolder{
private TextView textView;
private CheckBox checkBox;
}
}
} 3.3 使用ArrayActivity實現的例子
1.新建List資料集合
package com.example.zhengxie.demo_testcase;
/**
*
*/
public class Model {
private String name;
private boolean selected;
public Model(String name) {
this.name = name;
selected = false;
}
public String getName() {
return name;
}
public boolean isSelected() {
return selected;
}
public void setName(String name) {
this.name = name;
}
public void setSelected(boolean selected) {
this.selected = selected;
}
}2.新建ListActivity
package com.example.zhengxie.demo_testcase;
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import java.util.ArrayList;
import java.util.List;
/**
*
*/
public class MyList extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ArrayAdapter<Model> adapter = new myArrayAdapter<Model>(this, getModel());
setListAdapter(adapter);
}
private List<Model> getModel() {
List<Model> list = new ArrayList<Model>();
list.add(get("電信"));
list.add(get("移動"));
list.add(get("聯通"));
list.get(1).setSelected(true);
return list;
}
private Model get(String s) {
return new Model(s);
}
}3.建立adater類：myArrayAdapter.java
package com.example.zhengxie.demo_testcase;
import android.app.Activity;
import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.TextView;
import java.util.List;
/**
*
*/
public class myArrayAdapter<T> extends ArrayAdapter<Model> {
private final List<Model> list;
private final Activity context;
public myArrayAdapter(Activity context, List<Model> model) {
super(context, R.layout.rowbuttonlayout, model);
this.list = model;
this.context = context;
}
static class ViewHolder {
protected TextView textView;
protected CheckBox checkBox;
}
@NonNull
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.rowbuttonlayout, null);
final ViewHolder viewHolder = new ViewHolder();
viewHolder.textView = (TextView) view.findViewById(R.id.label);
viewHolder.checkBox = (CheckBox) view.findViewById(R.id.check);
viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (!buttonView.isPressed()) return;
Model element = (Model) viewHolder.checkBox.getTag();
element.setSelected(buttonView.isChecked());
}
});
view.setTag(viewHolder);
viewHolder.checkBox.setTag(list.get(position));
} else {
view = convertView;
((ViewHolder) view.getTag()).checkBox.setTag(list.get(position));
}
ViewHolder holder = (ViewHolder) view.getTag();
holder.textView.setText(list.get(position).getName());
holder.checkBox.setChecked(list.get(position).isSelected());
return view;
}
}4.RecyclerView
上面介紹完了ListView的常用顯示方式和技巧。下面進行一個當前最火的RecyclerView，這個實現類擁有著很多有點，
基本解決了ListView的一些缺陷，比如：需要手動重寫ViewHolder，對於item的動畫操作也需要很複雜的邏輯去實現等等。
下面我將用自己實現的一個例項為大家介紹：
1.新建RecyclerView的xml資源：
<?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:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="wrap_content"
tools:context="com.example.zhengxie.recyclerview.MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/rw_main"
android:layout_width="match_parent"
android:layout_centerHorizontal="true"
android:background="#000000"
android:layout_height="wrap_content"
>
</android.support.v7.widget.RecyclerView>
</RelativeLayout>2.新建類，對於RecyclerView進行初始化：
package com.example.zhengxie.recyclerview;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.animation.Animation;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private MyAdapter mMyAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//第一步：宣告RecyclerView
mRecyclerView = (RecyclerView) findViewById(R.id.rw_main);
//第二步：設定佈局的格式：LinearLayoutManager是水平顯示(如果要建立一個自定義佈局管理器，請擴充套件 RecyclerView.LayoutManager 類別)
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
//第三步：宣告一個Adapter
mMyAdapter = new MyAdapter(this, initData());
//繫結一個自定義的分割線
mRecyclerView.addItemDecoration(new MyItemDivider(this,R.drawable.shape));
//第四步：繫結adapter
mRecyclerView.setAdapter(mMyAdapter);
}
//第五步：宣告一個ArrayList陣列儲存資料
private List<String> initData() {
List<String> datas = new ArrayList<>();
for (int i = 0; i <= 40; i++) {
datas.add("Item:"+i);
}
return datas;
}
}3.初始化adapter：MyAdapter.java類
package com.example.zhengxie.recyclerview;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.List;
/**
*
*/
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private List<String> datas;
private LayoutInflater inflater;
//第一步：建立建構函式需要的引數
public MyAdapter(Context context, List<String> datas) {
this.datas = datas;
//記第二步：初始化inflate
inflater = LayoutInflater.from(context);
}
//第三步：宣告MyViewHolder這個類,初始化每個資源
public class MyViewHolder extends RecyclerView.ViewHolder {
private TextView title;
//第五步：宣告每個item
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.rv_main_item_title);
}
}
//第四步：重寫createView
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
MyViewHolder holder = new MyViewHolder(inflater.inflate(R.layout.rv_main_item, parent, false));
return holder;
}
//第六步：這裡對資料進行賦值操作
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.title.setText(datas.get(position));
}
@Override
public int getItemCount() {
return datas.size();
}
}
4.新增一個Decoratoin的shape：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:centerColor="#FF00FF00"
android:endColor="#FF0000FF"
android:startColor="#FFFF0000"
android:type="linear"
>
</gradient>
<size
android:height="1dp">
</size>
</shape>5.新增addItemDecoration類：MyItemDivider.java
package com.example.zhengxie.recyclerview;
import android.content.Context;
import android.content.res.Configuration;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.RecyclerView;
import android.view.View;
/**
*
*/
public class MyItemDivider extends RecyclerView.ItemDecoration{
private Drawable mDrawable;
public MyItemDivider(Context context, int resId) {
mDrawable = context.getResources().getDrawable(resId);
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
int left = parent.getPaddingLeft();//左邊距
int right = parent.getWidth() - parent.getPaddingRight();//右邊距
int childCount = parent.getChildCount();//獲得當前首次重新整理時頁面的item個數
for (int i = 0; i < childCount; i++) {
View child = parent.getChildAt(i);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
int top = child.getBottom() + params.bottomMargin;//獲得要畫decoration的上高度
int bottom = top + mDrawable.getIntrinsicHeight();//獲得要畫decoration下高度
mDrawable.setBounds(left, top, right, bottom);
mDrawable.draw(c);
}
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
outRect.set(0,0,0,mDrawable.getIntrinsicWidth());
}
}5.附加
對於RecyclerView中實現的Drawable的left,top,right,botton這裡做一下說明：
這樣大家就更容易更方便的理解Drawable方法在Android系統裡的繪製圖片的模式和座標位置了。