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学习适配器有一段时间了,现在对BaseAdapter的优化和要是项目中用到的适配其很多的话,完全可以建立一个SimpleBaseAdapter(继承自BaseAdapter),方便扩展.
主布局代码:
1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 android:layout_width="match_parent" 4 android:layout_height="match_parent" 5 android:orientation="vertical" 6 tools:context=".MainActivity"> 7 8 <ListView 9 android:id="@+id/listview" 10 android:layout_width="wrap_content" 11 android:layout_height="wrap_content" 12 /> 13 14 </LinearLayout>
item的布局:
1 <?xml version="1.0" encoding="utf-8"?> 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 3 android:layout_width="match_parent" 4 android:layout_height="wrap_content" 5 android:background="@drawable/bread__selector_pink_item" 6 android:orientation="horizontal" 7 android:gravity="center" 8 android:padding="10dp"> 9 10 <RelativeLayout 11 android:id="@+id/shop_info" 12 android:layout_width="fill_parent" 13 android:layout_height="wrap_content" 14 android:gravity="center_vertical" 15 android:paddingRight="12dp" 16 android:paddingLeft="12dp"> 17 18 <TextView 19 android:id="@+id/student_name" 20 android:layout_width="match_parent" 21 android:layout_height="wrap_content" 22 android:text="东海堂天河公园店" 23 android:textSize="14sp" /> 24 25 <TextView 26 android:id="@+id/student_addr" 27 android:layout_width="match_parent" 28 android:layout_height="wrap_content" 29 android:layout_below="@+id/student_name" 30 android:layout_marginTop="10dp" 31 android:text="广州天河区建业路华翠街" 32 android:textColor="@color/font_gray" 33 android:textSize="10sp" /> 34 35 </RelativeLayout> 36 37 </LinearLayout>
现在来说说BaseAdapter的优化,目前通用的优化就是ViewHolder,在getView()方法中,首次对convertView非空的处理,convertView会绑定一个ViewHolder对象，这个viewHolder主要用于帮convertView存储布局中的控件。了解这个就可以了.
来看看BaseAdapter的写法:
1 package com.fightzhao.myadapter1.ui.adapter; 2 3 import android.content.Context; 4 import android.view.LayoutInflater; 5 import android.view.View; 6 import android.view.ViewGroup; 7 import android.widget.BaseAdapter; 8 import android.widget.TextView; 9 10 import com.fightzhao.myadapter1.R; 11 import com.fightzhao.myadapter1.dao.Student; 12 13 import java.util.ArrayList; 14 15 /** 16 * Created by fightzhao on 15-9-16. 17 */ 18 public class FirstAdapter extends BaseAdapter { 19 private ArrayList<Student> data; 20 private Context context; 21 // private Student chosenStudent; 22 23 public FirstAdapter(Context context, ArrayList<Student> data) { 24 this.context = context; 25 this.data = data == null ? new ArrayList<Student>() : data; 26 } 27 28 @Override 29 public int getCount() { 30 return data.size(); 31 } 32 33 @Override 34 public Object getItem(int position) { 35 if (position > data.size()) 36 return null; 37 return data.get(position); 38 } 39 40 @Override 41 public long getItemId(int position) { 42 return position; 43 } 44 45 @Override 46 public View getView(int position, View convertView, ViewGroup parent) { 47 ViewHolder holder; 48 if (null == convertView) { 49 convertView = LayoutInflater.from(context).inflate(R.layout.item_student, null); 50 holder = new ViewHolder(); 51 holder.student_name = (TextView) convertView.findViewById(R.id.student_name); 52 holder.student_addr = (TextView) convertView.findViewById(R.id.student_addr); 53 convertView.setTag(holder); 54 } else { 55 holder = (ViewHolder) convertView.getTag(); 56 } 57 holder.student_name.setText(data.get(position).getName()); 58 holder.student_addr.setText(data.get(position).getAddr()); 59 return convertView; 60 } 61 62 class ViewHolder { 63 TextView student_name; 64 TextView student_addr; 65 } 66 // public void setChosenStudent(Student student){ 67 // chosenStudent = student; 68 // notifyDataSetChanged(); 69 // } 70 // public Student getChosenStudent(){ 71 // return chosenStudent; 72 // } 73 }
这里的Student就是以模拟数据,不贴代码了.
如果项目中用到的适配器不是很多的话,用这个是没问题的,但是,为了更好扩展的话,看来下张奇大大的做法,这里直接引用:
代码:
1 package com.fightzhao.myadapter1.ui.adapter; 2 3 import android.content.Context; 4 import android.util.SparseArray; 5 import android.view.View; 6 import android.view.ViewGroup; 7 import android.widget.BaseAdapter; 8 9 import java.util.ArrayList; 10 import java.util.List; 11 12 /** 13 * Created by fightzhao on 15-9-16. 14 */ 15 public abstract class SimpleBaseAdapter<T> extends BaseAdapter { 16 protected Context context; 17 protected List<T> data; 18 19 public SimpleBaseAdapter(Context context, List<T> data) { 20 this.context = context; 21 this.data = data == null ? new ArrayList<T>() : new ArrayList<T>(data); 22 } 23 24 @Override 25 public int getCount() { 26 return data.size(); 27 } 28 29 @Override 30 public Object getItem(int position) { 31 if (position >= data.size()) 32 return null; 33 return data.get(position); 34 } 35 36 @Override 37 public long getItemId(int position) { 38 return position; 39 } 40 41 /** 42 * 该方法需要子类实现，需要返回item布局的resource id 43 * 44 * @return 45 */ 46 public abstract int getItemResource(); 47 48 /** 49 * 使用该getItemView方法替换原来的getView方法，需要子类实现 50 * 51 * @param position 52 * @param convertView 53 * @param holder 54 * @return 55 */ 56 public abstract View getItemView(int position, View convertView, ViewHolder holder); 57 58 @SuppressWarnings("unchecked") 59 @Override 60 public View getView(int position, View convertView, ViewGroup parent) { 61 ViewHolder holder; 62 if (null == convertView) { 63 convertView = View.inflate(context, getItemResource(), null); 64 holder = new ViewHolder(convertView); 65 convertView.setTag(holder); 66 } else { 67 holder = (ViewHolder) convertView.getTag(); 68 } 69 return getItemView(position, convertView, holder); 70 } 71 72 public class ViewHolder { 73 private SparseArray<View> views = new SparseArray<View>(); 74 private View convertView; 75 public ViewHolder(View convertView) { 76 this.convertView = convertView; 77 } 78 /** 79 * 通过控件的Id获取对应的控件，如果没有则加入views 80 * 81 * @param resId 82 * @param <T> 83 * @return 84 */ 85 @SuppressWarnings("unchecked") 86 public <T extends View> T getView(int resId) { 87 View v = views.get(resId); 88 if (null == v) { 89 v = convertView.findViewById(resId); 90 views.put(resId, v); 91 } 92 return (T) v; 93 } 94 } 95 96 public void add(T t) { 97 data.add(t); 98 notifyDataSetChanged(); 99 } 100 101 public void addAll(List<T> elem) { 102 data.addAll(elem); 103 notifyDataSetChanged(); 104 } 105 106 public void remove(T elem) { 107 data.remove(elem); 108 notifyDataSetChanged(); 109 } 110 111 public void remove(int index) { 112 data.remove(index); 113 notifyDataSetChanged(); 114 } 115 116 public void replaceAll(List<T> elem) { 117 data.clear(); 118 data.addAll(elem); 119 notifyDataSetChanged(); 120 } 121 }
使用:
1 package com.fightzhao.myadapter1.ui.adapter; 2 3 import android.content.Context; 4 import android.view.View; 5 import android.widget.TextView; 6 7 import com.fightzhao.myadapter1.R; 8 import com.fightzhao.myadapter1.dao.Student; 9 10 import java.util.List; 11 12 /** 13 * Created by fightzhao on 15-9-16. 14 */ 15 public class SecoundAdapter extends SimpleBaseAdapter<Student> { 16 public SecoundAdapter(Context context, List<Student> data) { 17 super(context, data); 18 } 19 @Override 20 public int getItemResource() { 21 return R.layout.item_student; 22 } 23 @Override 24 public View getItemView(int position, View convertView, ViewHolder holder) { 25 TextView student_name = holder.getView(R.id.student_name); 26 TextView student_addr = holder.getView(R.id.student_addr); 27 student_name.setText(data.get(position).getName()); 28 student_addr.setText(data.get(position).getAddr()); 29 return convertView; 30 } 31 }
之后在MainActivity中使用即可:
1 package com.fightzhao.myadapter1; 2 3 import android.app.Activity; 4 import android.os.Bundle; 5 import android.view.View; 6 import android.widget.AdapterView; 7 import android.widget.ListView; 8 import android.widget.Toast; 9 10 import com.fightzhao.myadapter1.dao.Student; 11 import com.fightzhao.myadapter1.ui.adapter.FirstAdapter; 12 import com.fightzhao.myadapter1.ui.adapter.SecoundAdapter; 13 14 import java.util.ArrayList; 15 16 public class MainActivity extends Activity { 17 private ListView listView; 18 private ArrayList<Student> data; 19 private FirstAdapter firstAdapter; 20 SecoundAdapter secoundAdapter; 21 22 @Override 23 protected void onCreate(Bundle savedInstanceState) { 24 super.onCreate(savedInstanceState); 25 setContentView(R.layout.activity_main); 26 initView(); 27 initData(); 28 // firstAdapter = new FirstAdapter(this,data); 29 // listView.setAdapter(firstAdapter); 30 secoundAdapter =new SecoundAdapter(this,data); 31 listView.setAdapter(secoundAdapter); 32 33 } 34 35 36 private void initView() { 37 listView = (ListView) findViewById(R.id.listview); 38 listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 39 @Override 40 public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 41 Student student = (Student) parent.getItemAtPosition(position); 42 // firstAdapter.setChosenStudent(student); 43 if(view.hasFocusable()){ 44 view.setBackgroundResource(R.color.item_pink); 45 } 46 47 Toast.makeText(getApplicationContext(),"sad",Toast.LENGTH_SHORT).show(); 48 } 49 }); 50 51 } 52 53 54 55 56 57 private void initData() { 58 data = new ArrayList<>(); 59 data.add(new Student("张三", "北京")); 60 data.add(new Student("张学友", "香港")); 61 data.add(new Student("周杰伦", "台湾")); 62 data.add(new Student("梁朝伟", "香港")); 63 data.add(new Student("李四", "合肥")); 64 65 66 } 67 68 }
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原文地址：http://www.cnblogs.com/fightzhao/p/4813143.html
