Android基础类之BaseAdapter
Android基础类之BaseAdapter
BaseAdapter就Android应用程序中经常用到的基础数据适配器,它的主要用途是将一组数据传到像ListView、Spinner、Gallery及GridView等UI显示组件,它是继承自接口类Adapter,
1、Adapter类简介
1)、Adapter相关类结构如下图所示:
自定义Adapter子类,就需要实现上面几个方法,其中最重要的是getView()方法,它是将获取数据后的View组件返回,如ListView中每一行里的TextView、Gallery中的每个ImageView。
2)、Adapter在Android应用程序中起着非常重要的作用,应用也非常广泛,它可看作是数据源和UI组件之间的桥梁,其中Adapter、数据和UI之间的关系,可以用下图表示:
3)、常用子类
2、BaseAdapter简介 BaseAdapter是实现了ListAdapter和SpinnerAdapter两个接口,当然它也可以直接给ListView和Spinner等UI组件直接提供数据。
相关类结构如下图所示:
3、示例
示例一:Gallery显示一组图片
运行结果:
![](https://pic002.cnblogs.com/images/2011/269610/2011040523501671.png)
布局文件:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <Gallery android:id="@+id/gallery1" android:layout_width="match_parent" android:spacing="5px" android:layout_height="wrap_content" ></Gallery> <ImageView android:id="@+id/iv" android:layout_gravity="center_vertical" android:layout_marginTop="20px" android:layout_width="320px" android:layout_height="320px" ></ImageView> </LinearLayout>
MainActivity类:
package com.magc.adapter;
import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.view.View.OnClickListener; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.Gallery; import android.widget.ImageView; import android.widget.AdapterView.OnItemClickListener;
public class MainActivity extends Activity { private Gallery gallery; private ImageView imgview; private int[] imgs = {R.drawable.a6,R.drawable.a1,R.drawable.a2,R.drawable.a3,R.drawable.a4,R.drawable.a5}; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imgview = (ImageView)findViewById(R.id.iv); gallery = (Gallery)findViewById(R.id.gallery1); MyImgAdapter adapter = new MyImgAdapter(this); gallery.setAdapter(adapter); gallery.setOnItemClickListener(new OnItemClickListener() { //用户点击图片时,将该图片的ResourceID设到下面的ImageView中去, @Override public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) { imgview.setImageResource(imgs[position]); } }); } class MyImgAdapter extends BaseAdapter { //自定义图片Adapter以内部类形式存在于MainActivity中,方便访问MainActivity中的各个变量,特别是imgs数组 private Context context;//用于接收传递过来的Context对象 public MyImgAdapter(Context context) { super(); this.context = context; }
/* (non-Javadoc) * @see android.widget.Adapter#getCount() */ @Override public int getCount() { return imgs.length; }
/* (non-Javadoc) * @see android.widget.Adapter#getItem(int) */ @Override public Object getItem(int position) { return position; }
/* (non-Javadoc) * @see android.widget.Adapter#getItemId(int) */ @Override public long getItemId(int position) { return position; }
/* (non-Javadoc) * @see android.widget.Adapter#getView(int, android.view.View, android.view.ViewGroup) */ @Override public View getView(int position, View convertView, ViewGroup parent) { //针对每一个数据(即每一个图片ID)创建一个ImageView实例, ImageView iv = new ImageView(context);//针对外面传递过来的Context变量, iv.setImageResource(imgs[position]); Log.i("magc", String.valueOf(imgs[position])); iv.setLayoutParams(new Gallery.LayoutParams(80, 80));//设置Gallery中每一个图片的大小为80*80。 iv.setScaleType(ImageView.ScaleType.FIT_XY); return iv; }
} }
import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.view.View.OnClickListener; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.Gallery; import android.widget.ImageView; import android.widget.AdapterView.OnItemClickListener;
public class MainActivity extends Activity { private Gallery gallery; private ImageView imgview; private int[] imgs = {R.drawable.a6,R.drawable.a1,R.drawable.a2,R.drawable.a3,R.drawable.a4,R.drawable.a5}; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imgview = (ImageView)findViewById(R.id.iv); gallery = (Gallery)findViewById(R.id.gallery1); MyImgAdapter adapter = new MyImgAdapter(this); gallery.setAdapter(adapter); gallery.setOnItemClickListener(new OnItemClickListener() { //用户点击图片时,将该图片的ResourceID设到下面的ImageView中去, @Override public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) { imgview.setImageResource(imgs[position]); } }); } class MyImgAdapter extends BaseAdapter { //自定义图片Adapter以内部类形式存在于MainActivity中,方便访问MainActivity中的各个变量,特别是imgs数组 private Context context;//用于接收传递过来的Context对象 public MyImgAdapter(Context context) { super(); this.context = context; }
/* (non-Javadoc) * @see android.widget.Adapter#getCount() */ @Override public int getCount() { return imgs.length; }
/* (non-Javadoc) * @see android.widget.Adapter#getItem(int) */ @Override public Object getItem(int position) { return position; }
/* (non-Javadoc) * @see android.widget.Adapter#getItemId(int) */ @Override public long getItemId(int position) { return position; }
/* (non-Javadoc) * @see android.widget.Adapter#getView(int, android.view.View, android.view.ViewGroup) */ @Override public View getView(int position, View convertView, ViewGroup parent) { //针对每一个数据(即每一个图片ID)创建一个ImageView实例, ImageView iv = new ImageView(context);//针对外面传递过来的Context变量, iv.setImageResource(imgs[position]); Log.i("magc", String.valueOf(imgs[position])); iv.setLayoutParams(new Gallery.LayoutParams(80, 80));//设置Gallery中每一个图片的大小为80*80。 iv.setScaleType(ImageView.ScaleType.FIT_XY); return iv; }
} }