Android之图片浏览

参考android API demo,学习一下利用ImageSwitcher结合Gallery来进行图片的预览与浏览。

首先是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="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>

layout里面用到了前面所说的两个控件，ImageSwitcher用啦显示全图，Gallery用来显示缩略图。Gallery上一篇博客已经介绍过了，这里不再多说，着重看看ImageSwitcher,在ImageSwitcher1中需要实现ViewSwitcher.ViewFactory这个接口，这个接口里有个方法makeView，这样就产生了用来显示图片的view. ImageSwitcher调用过程是这样的，首先要有一个Factory为它提供一个View，然后ImageSwitcher就可以初始化各种资源了。注意在使用一个ImageSwitcher之前，一定要调用setFactory方法，要不setImageResource这个方法会报空指针异常。
下面是代码：

package com.zx.imageswitcher; import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.view.View; import android.view.ViewGroup; 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.ViewSwitcher; import android.widget.Gallery.LayoutParams; public class ImageSwitcherTest extends Activity implements AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory{          private ImageSwitcher mSwitcher;          private Integer[] mThumbIds = {             R.drawable.sample_thumb_0, R.drawable.sample_thumb_1,             R.drawable.sample_thumb_2, R.drawable.sample_thumb_3,             R.drawable.sample_thumb_4, R.drawable.sample_thumb_5,             R.drawable.sample_thumb_6, R.drawable.sample_thumb_7};     private Integer[] mImageIds = {             R.drawable.sample_0, R.drawable.sample_1, R.drawable.sample_2,             R.drawable.sample_3, R.drawable.sample_4, R.drawable.sample_5,             R.drawable.sample_6, R.drawable.sample_7};          /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         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);     }     /*      *           * override for ViewSwitcher.ViewFactory#makeView()      */     public 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;     }     /*      * override for      * AdapterView.OnItemSelectedListener#onItemSelected()      */     public void onItemSelected(AdapterView parent, View v, int position, long id) {         mSwitcher.setImageResource(mImageIds[position]);     }     /*      * override for AdapterView.OnItemSelectedListener#onNothingSelected()      */     public void onNothingSelected(AdapterView<?> arg0) {         // TODO Auto-generated method stub              }          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.picture_frame);             return i;         }         private Context mContext;     } }

从代码中看到还实现了AdapterView.OnItemSelectedListener，这样就需要重写onItemSelected()方法，然后在该方法中：mSwitcher.setImageResource(mImageIds[position]);这样就实现了图片在ImageSwitcher中的切换。
其他的就比较简单了，不再多说。