Android UI控件系列：Gallery（画廊视图）

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Gallery能够水平显示其内容，一般用来浏览图片，被选中的选项位于中间，并且可以相应事件显示信息。下面结合ImageSwitcher组件来实现一个通过缩略图来浏览图片的程序，具体步骤如下

第一步：

创建一个Andorid工程”GalleryTest”，该工程的入口是Activity类GalleryTest继承Activity并实现OnItemSelectedListener和ViewFactory接口，来实现图片和视图的创建

package org.hualang.Gallery;import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ViewSwitcher.ViewFactory;
//继承Activity，实现onItemSelectedListener和ViewFactory接口
public class GalleryTest extends Activity implements OnItemSelectedListener,ViewFactory{/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);}@Overridepublic View makeView() {// TODO Auto-generated method stubreturn null;}@Overridepublic void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,long arg3) {// TODO Auto-generated method stub}@Overridepublic void onNothingSelected(AdapterView<?> arg0) {// TODO Auto-generated method stub}
}

第二步：

在工程的res\drawable\目录下添加7张图片和对应的缩略图

第三步：

在工程res\layout\目录下创建一个布局文件main.xml，在其中那个添加一个Gallery组件和一个ImageSwitcher组件，并设置相应的属性

<?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">
<ImageSwitcher android:id="@+id/switcher"android:layout_width="fill_parent"android:layout_height="fill_parent"android:layout_alignParentTop="true"android:layout_alignParentLeft="true"/><Gallery android:id="@+id/gallery"android:background="#55000000"android:layout_width="fill_parent"android:layout_height="60dp"android:layout_alignParentBottom="true"android:layout_alignParentLeft="true"android:gravity="center_vertical"android:spacing="16dp"/>
</LinearLayout>

第四步：在GalleryTest顶部声明使用到的ImageSwitcher实例图片资源Integer数组

public class GalleryTest extends Activity implements OnItemSelectedListener,ViewFactory{/** Called when the activity is first created. *///声明ImageSwitcherprivate ImageSwitcher switcher;//缩略图片id数组private Integer[] thumbids={R.drawable.thumb0,R.drawable.thumb1,R.drawable.thumb2,R.drawable.thumb3,R.drawable.thumb4,R.drawable.thumb5,R.drawable.thumb6,R.drawable.thumb7};//图片id数组private Integer[] imgids={R.drawable.img0,R.drawable.img1,R.drawable.img2,R.drawable.img3,R.drawable.img4,R.drawable.img5,R.drawable.img6,R.drawable.img7};

第五步：

在GalleryTest的onCreate()方法中，将窗口样式设置为无标题，设置当前布局视图，获得ImageSwitcher实例，并设置渐进渐出动画，获得Gallery实例

public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);//设置窗口特征无标题requestWindowFeature(Window.FEATURE_NO_TITLE);setContentView(R.layout.main);//通过findViewById方法获得ImageSwitcher对象switcher=(ImageSwitcher)findViewById(R.id.switcher);//为ImageSwitcher设置工厂switcher.setFactory(this);//设置动画渐入效果switcher.setInAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));//设置动画渐出效果switcher.setOutAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_out));//通过findViewById方法获得Gallery对象Gallery g=(Gallery)findViewById(R.id.gallery);}

第六步：

创建内部类ImageAdapter，该类继承BaseAdapter，为Gallery设置Adapter实例

public class ImageAdapter extends BaseAdapter {//构造方法public ImageAdapter(Context c) {mContext = c;}//获得数量public int getCount() {return thumbids.length;}//获得当前选项public Object getItem(int position) {return position;}//获得当前选项IDpublic long getItemId(int position) {return position;}//获得View对象public View getView(int position, View convertView, ViewGroup parent) {//实例化ImageView对象ImageView i = new ImageView(mContext);//设置缩略图片资源i.setImageResource(thumbids[position]);//设置边界对齐i.setAdjustViewBounds(true);//设置布局参数i.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));//设置背景资源i.setBackgroundResource(R.drawable.picturefrom);return i;}private Context mContext;}

第七步：

实现onItemSelected()方法，更换图片

@Overridepublic void onItemSelected(AdapterView<?> adapter, View v, int position,long id) {switcher.setImageResource(imgids[position]);}

第八步：

实现makeView()方法，为ImageView设置布局格式

@Overridepublic View makeView() {// TODO Auto-generated method stub//创建ImageViewImageView i=new ImageView(this);//设置背景颜色i.setBackgroundColor(0xFF000000);//设置精度类型i.setScaleType(ImageView.ScaleType.FIT_CENTER);//设置布局参数i.setLayoutParams(new ImageSwitcher.LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT));return i;}

第九步：

为Gallery添加Adapter并添加OnItemSelectedListener监听器

g.setAdapter(new ImageAdapter(this));g.setOnItemSelectedListener(this);

至此，全部，结束，运行结果如下

完整源代码：

package org.hualang.Gallery;import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Gallery.LayoutParams;
import android.widget.ViewSwitcher.ViewFactory;public class GalleryTest extends Activity implements OnItemSelectedListener,ViewFactory {private ImageSwitcher mSwitcher;private Integer[] mThumbIds = { R.drawable.thumb0,R.drawable.thumb1, R.drawable.thumb2,R.drawable.thumb3, R.drawable.thumb4,R.drawable.thumb5, R.drawable.thumb6,R.drawable.thumb7 };private Integer[] mImageIds = { R.drawable.img0, R.drawable.img1,R.drawable.img2, R.drawable.img3, R.drawable.img4,R.drawable.img5, R.drawable.img6, R.drawable.img7 };@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);requestWindowFeature(Window.FEATURE_NO_TITLE);setContentView(R.layout.main);mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);mSwitcher.setFactory(this);mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,android.R.anim.fade_in));mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,android.R.anim.fade_out));Gallery g = (Gallery) findViewById(R.id.gallery);g.setAdapter(new ImageAdapter(this));g.setOnItemSelectedListener(this);}public class ImageAdapter extends BaseAdapter {public ImageAdapter(Context c) {mContext = c;}public int getCount() {return mThumbIds.length;}public Object getItem(int position) {return position;}public long getItemId(int position) {return position;}public View getView(int position, View convertView, ViewGroup parent) {ImageView i = new ImageView(mContext);i.setImageResource(mThumbIds[position]);i.setAdjustViewBounds(true);i.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));i.setBackgroundResource(R.drawable.picturefrom);return i;}private Context mContext;}@Overridepublic void onItemSelected(AdapterView<?> adapter, View v, int position,long id) {mSwitcher.setImageResource(mImageIds[position]);}@Overridepublic void onNothingSelected(AdapterView<?> arg0) {}@Overridepublic View makeView() {ImageView i = new ImageView(this);i.setBackgroundColor(0xFF000000);i.setScaleType(ImageView.ScaleType.FIT_CENTER);i.setLayoutParams(new ImageSwitcher.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));return i;}
}

<?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="fill_parent">
<ImageSwitcher android:id="@+id/switcher"android:layout_width="fill_parent"android:layout_height="fill_parent"android:layout_alignParentTop="true"android:layout_alignParentLeft="true"/>
<Gallery android:id="@+id/gallery"android:background="#55000000"android:layout_width="fill_parent"android:layout_height="60dp"android:layout_alignParentBottom="true"android:layout_alignParentLeft="true"android:gravity="center_vertical"android:spacing="16dp"/>
</RelativeLayout>

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