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=""
    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。