android之路Gallery 画廊

Gallery是一个内部元素可以水平滚动，并且可以把当前选择的子元素定位在它中心的布局组件。

我们还是直接看看例子的运行效果。

1.新疆项目HelloGallery

2.把需要展示的图片放入res/drawable目录。woman01.jpg，woman02.jpg，woman03.jpg

3.res/layout/activity_main.xml文件的内容如下：

<FrameLayout  xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:id="@+id/FrameLayout01"   ><ImageView android:layout_width="match_parent"    android:layout_height="match_parent"    android:id="@+id/ImageView01"    android:src="@drawable/woman01"/><Gallery android:layout_width="match_parent"    android:layout_height="wrap_content"    android:id="@+id/gallery01"    android:spacing="5dp"/></FrameLayout >

我们使用FrameLayout来实现叠加效果，使用ImageView来显示大图，Gallery来展示画廊，android:spacing="5dp" 属性则是用来设置元素之间的间隔。

4.在res/values/目录中新建一个attrs.xml内容如下：

<?xml version="1.0" encoding="utf-8"?><resources>   <declare-styleable name="HelloGallery">         <attr name="android:galleryItemBackground">        </attr>   </declare-styleable></resources>

5.主activity,MainActivity的代码如下：

<pre name="code" class="java">package com.howlaa.hellogallery;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.View;import android.view.ViewGroup;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.BaseAdapter;import android.widget.Gallery;import android.widget.ImageView;import android.widget.Toast;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);final ImageView iv = (ImageView)findViewById(R.id.ImageView01);Gallery g = (Gallery) findViewById(R.id.gallery01);//设置图片匹配器        g.setAdapter(new ImageAdapter(this));        //设置AdapterView点击监听器，Gallery是AdapterView的子类        g.setOnItemClickListener(new OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view,                            int position, long id) {                    //显示点击的是第几张图片                    Toast.makeText(MainActivity.this, "" + position,                                    Toast.LENGTH_LONG).show();                    //设置背景部分的ImageView显示当前Item的图片                    iv.setImageResource(((ImageView)view).getId());            }    });} }

6.ImageAdapter的代码如下：

package com.howlaa.hellogallery;import android.content.Context;import android.content.res.TypedArray;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.Gallery;import android.widget.ImageView;import android.widget.SpinnerAdapter;public class ImageAdapter extends BaseAdapter {//Item的修饰背景    int mGalleryItemBackground;    //上下文对象    private Context mContext;    //图片数组    private Integer[] mImageIds ={R.drawable.woman01,R.drawable.woman02,R.drawable.woman03};  //构造方法    public ImageAdapter(Context c){            mContext = c;    //读取styleable资源    TypedArray a = mContext.obtainStyledAttributes(R.styleable.HelloGallery);    mGalleryItemBackground = a.getResourceId(            R.styleable.HelloGallery_android_galleryItemBackground, 0);    a.recycle();    }        @Overridepublic int getCount() { return mImageIds.length;}@Overridepublic Object getItem(int position) { return position;}@Overridepublic long getItemId(int position) {  return position;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {ImageView iv = new ImageView(mContext);iv.setImageResource(mImageIds[position]);  //给生成的ImageView设置Id，不设置的话Id都是-1        iv.setId(mImageIds[position]);        iv.setLayoutParams(new Gallery.LayoutParams(120, 160));        iv.setScaleType(ImageView.ScaleType.FIT_XY);        iv.setBackgroundResource(mGalleryItemBackground);return iv;}}