Adapter類的定義：
Adapter對象是AdapterView和底層數據見的橋梁。Adapter用于訪問數據項，并且負責為數據項生成視圖
AdapterView是一個抽象類，用于那些需要通過Adapter填充自身的視圖，其常見子類是ListView。顯示AdapterView時會調用Adapter的getView()方法創建并添加每個子條目的視圖。Adapter的getView()方法就是用來創建這些視圖的，Adapter并不會為每行數據都創建一個新視圖，而是提供了回收舊視圖的方法。運行機制簡單說就是當getView()方法被調用是，如果convertView參數不為null,就使用convertView，不用新建視圖，通過convertView.findViewById()方法獲取每個UI控件的引用，然后使用與當前項的位置綁定的數據來填充視圖
為了優化，使用ViewHolder模式，ViewHolder是一個靜態類，可以用于保存每行的視圖以避免每次調用getView時都會調用findViewById()
public class Hack25Activity extends ListActivity { private static final int MODEL_COUNT = 30; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setListAdapter(new ModelAdapter(this, 0, buildModels())); } private List<Model> buildModels() { final ArrayList<Model> ret = new ArrayList<Model>(MODEL_COUNT); for (int i = 0; i < MODEL_COUNT; i++) { final Model model = new Model(); model.setImage(R.mipmap.ic_launcher); model.setText1("Name " + i); model.setText2("Description " + i); ret.add(model); } return ret; }}Model.java
public class Model { private String mText1; private String mText2; private int mImageResId; public String getText1() { return mText1; } public void setText1(String text1) { mText1 = text1; } public String getText2() { return mText2; } public void setText2(String text2) { mText2 = text2; } public int getImage() { return mImageResId; } public void setImage(int imageResId) { mImageResId = imageResId; }}ModelAdapter.java
public class ModelAdapter extends ArrayAdapter<Model> { private LayoutInflater mInflater; public ModelAdapter(Context context, int textViewResourceId, List<Model> objects) { super(context, textViewResourceId, objects); mInflater = LayoutInflater.from(context); } @Override public View getView(int position, View convertView, ViewGroup parent) { final ViewHolder viewHolder; if (convertView == null) { convertView = mInflater.inflate(R.layout.row_layout, parent, false); viewHolder = new ViewHolder(); viewHolder.imageView = (ImageView) convertView .findViewById(R.id.image); viewHolder.text1 = (TextView) convertView .findViewById(R.id.text1); viewHolder.text2 = (TextView) convertView .findViewById(R.id.text2); convertView.setTag(viewHolder); } else { viewHolder = (ViewHolder) convertView.getTag(); } Model model = getItem(position); viewHolder.imageView.setImageResource(model.getImage()); viewHolder.text1.setText(model.getText1()); viewHolder.text2.setText(model.getText2()); return convertView; } private static class ViewHolder { public ImageView imageView; public TextView text1; public TextView text2; }}row_layout.xml
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" > <ImageView android:id="@+id/image" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_centerVertical="true" /> <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_centerVertical="true" android:layout_toRightOf="@id/image" android:orientation="vertical" > <TextView android:id="@+id/text1" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/text2" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </LinearLayout></RelativeLayout>
以上代碼就基本實現了功能
不過每次都自定義ViewHolder比較繁瑣，在網上找了一個工具類，共享一下
ViewHolder.java
public class ViewHolder { public static <T extends View> T get(View view, int id) { SparseArray<View> viewHolder = (SparseArray<View>) view.getTag(); if (viewHolder == null) { viewHolder = new SparseArray<View>(); view.setTag(viewHolder); } View childView = viewHolder.get(id); if (childView == null) { childView = view.findViewById(id); viewHolder.put(id, childView); } return (T) childView; } } 使用方法：
@Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = LayoutInflater.from(context) .inflate(R.layout.banana_phone, parent, false); } ImageView bananaView = ViewHolder.get(convertView, R.id.banana); TextView phoneView = ViewHolder.get(convertView, R.id.phone); BananaPhone bananaPhone = getItem(position); phoneView.setText(bananaPhone.getPhone()); bananaView.setImageResource(bananaPhone.getBanana()); return convertView; } 以上這篇Android 通過ViewHolder優化適配器的實現方法(必看)就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支持VEVB武林網。
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