写一篇利用Picasso图片加载框架，PhotoView图片缩放控件以及ViewPager的图片浏览器

首先建立依赖：

在这里我们加入PhotoView和picasso的依赖

//PhotoView       
compile 'com.github.chrisbanes.photoview:library:+'
//picasso
compile 'com.squareup.picasso:picasso:+'

然后我们写一个图片列表展示的首页

图片的展示页采用RecyclerView去展示,布局文件如下所示

<android.support.v7.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</android.support.v7.widget.RecyclerView>

加入数据，图片是从网上找的几张图片，加入数据集合中

images.add("http://img3.imgtn.bdimg.com/it/u=3993672553,267575750&fm=21&gp=0.jpg");
images.add("http://img5.imgtn.bdimg.com/it/u=2652905594,2769975769&fm=21&gp=0.jpg");
images.add("http://i.zeze.com/attachment/forum/201511/06/180208mwwxx8oer7wirv89.jpg");
images.add("http://imgsrc.baidu.com/forum/w%3D580/sign=fe8a7e7f78ec54e741ec1a1689399bfd/4b3f9682d158ccbfb334467b1ad8bc3eb33541cd.jpg");
images.add("http://static.wgpet.com/editor/attached/image/20141124/20141124225933_71813.jpg");
images.add("http://v1.qzone.cc/pic/201405/25/13/57/5381864e3b8af886.jpg%21600x600.jpg");
images.add("http://wanzao2.b0.upaiyun.com/system/pictures/23660313/original/8d4f08e50be02ae3.png");
images.add("http://zyline-photo.qiniudn.com/1392705051156.jpg");

为RecyclerView创建Adapter，在ViewHolder中加入列表的点击事件

package com.jelly.imagebrowse.adapter;    

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.jelly.imagebrowse.R;
import com.squareup.picasso.Picasso;

import java.util.List;

/**
 *  图片列表适配器
 * Created by Jelly on 2016/9/3.
 */
public class ImageRecyclerAdapter extends RecyclerView.Adapter<ImageRecyclerAdapter.ImageHolder>{

private List<String> dataList;
private Context context;
private LayoutInflater inflater;
private OnRecyclerItemClickListener itemClickListener;

public ImageRecyclerAdapter(Context context,List<String> dataList) {
    this.context = context;
    this.dataList = dataList;
    inflater = LayoutInflater.from(context);
}

@Override
public int getItemCount() {
    return dataList.size();
}

@Override
public ImageHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    return new ImageHolder(inflater.inflate(R.layout.item_image,parent,false),itemClickListener);
}

@Override
public void onBindViewHolder(ImageHolder holder, int position) {
    Picasso.with(context).load(dataList.get(position)).resize(200,200).centerCrop().into(holder.image);
}

public void setItemClickListener(OnRecyclerItemClickListener itemClickListener) {
    this.itemClickListener = itemClickListener;
}

public static class ImageHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

    private ImageView image;
    private OnRecyclerItemClickListener itemClickListener;

    public ImageHolder(View itemView,OnRecyclerItemClickListener itemClickListener) {
        super(itemView);
        this.itemClickListener = itemClickListener;
        itemView.setOnClickListener(this);
        image = (ImageView) itemView.findViewById(R.id.image);
    }

    @Override
    public void onClick(View v) {
        if(itemClickListener == null) return;
        itemClickListener.click(itemView,getAdapterPosition());
    }

}
}

Activity中设置RecyclerView，加入RecyclerView的点击事件，进入图片浏览的Activity

rv.setLayoutManager(new GridLayoutManager(this,3));
rv.setItemAnimator(new DefaultItemAnimator());
adapter = new ImageRecyclerAdapter(this,images);
adapter.setItemClickListener(new OnRecyclerItemClickListener() {
    @Override
    public void click(View item, int position) {
        ImageBrowseActivity.startActivity(MainActivity.this, (ArrayList<String>) images,position);
    }
});
rv.setAdapter(adapter);

显示效果

图片展示.png

图片浏览Activity

在上一Activity上传入需要显示的图片的集合和显示的Position

public static void startActivity(Context context, ArrayList<String> images, int position){
    Intent intent = new Intent(context,ImageBrowseActivity.class);
    intent.putStringArrayListExtra("images",images);
    intent.putExtra("position",position);
    context.startActivity(intent);
}

布局Activity，显示图片的hint和保存按钮

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/black">

    <com.jelly.imagebrowse.view.ViewPagerFixed
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </com.jelly.imagebrowse.view.ViewPagerFixed>



    <TextView
        android:id="@+id/hint"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="20dp"
        android:layout_margin="10dp"
        android:layout_alignParentBottom="true"
        android:textColor="@android:color/white"
        android:text="0/0"/>

    <TextView
        android:id="@+id/save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="20dp"
        android:layout_margin="10dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:textColor="@android:color/white"
        android:text="保存"/>

</RelativeLayout>

在布局文件中使用的ViewPagerFixed，修复了在使用PhotoView时的一个Bug

package com.jelly.imagebrowse.view;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;

public class ViewPagerFixed extends android.support.v4.view.ViewPager {

    public ViewPagerFixed(Context context) {
        super(context);
    }

    public ViewPagerFixed(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        try {
            return super.onTouchEvent(ev);
        } catch (IllegalArgumentException ex) {
            ex.printStackTrace();
        }
        return false;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        try {
            return super.onInterceptTouchEvent(ev);
        } catch (IllegalArgumentException ex) {
            ex.printStackTrace();
        }
        return false;
    }
}

ViewPager的Adapter，这里使用SparseArray进行缓存，PhotoViewAttacher设置ImageView可以放大缩小 ，使用Picasso加载图片，Bitmap.Config.RGB_565提高图片加载效率，在Picasso的回调中调用PhotoViewAttacher的Update刷新，不刷新的话会导致图片错位。

package com.jelly.imagebrowse.adapter;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.support.v4.view.PagerAdapter;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.jelly.imagebrowse.R;
import com.squareup.picasso.Callback;
import com.squareup.picasso.Picasso;

import java.util.List;

import uk.co.senab.photoview.PhotoViewAttacher;


/**
 * 图片浏览ViewPageAdapter
 * Created by Jelly on 2016/3/10.
 */
public class ViewPageAdapter extends PagerAdapter {
    private Context context;
    private List<String> images;
    private SparseArray<View> cacheView;
    private ViewGroup containerTemp;

    public ViewPageAdapter(Context context, List<String> images) {
        this.context = context;
        this.images = images;
        cacheView = new SparseArray<>(images.size());
    }

    @Override
    public Object instantiateItem(final ViewGroup container, int position) {
        if(containerTemp == null) containerTemp = container;

        View view = cacheView.get(position);

        if(view == null){
            view = LayoutInflater.from(context).inflate(R.layout.vp_item_image,container,false);
            view.setTag(position);
            final ImageView image = (ImageView) view.findViewById(R.id.image);
            final PhotoViewAttacher photoViewAttacher = new PhotoViewAttacher(image);

            Picasso.with(context).load(images.get(position)).config(Bitmap.Config.RGB_565).into(image, new Callback() {
                @Override
                public void onSuccess() {
                    photoViewAttacher.update();
                }

                @Override
                public void onError() {

                }
            });

            photoViewAttacher.setOnPhotoTapListener(new PhotoViewAttacher.OnPhotoTapListener() {
                @Override
                public void onPhotoTap(View view, float x, float y) {
                    Activity activity = (Activity) context;
                    activity.finish();
                }
            });
            cacheView.put(position,view);
        }
        container.addView(view);
        return view;
    }

    @Override
    public int getCount() {
        return images.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        View view = (View) object;
        container.removeView(view);
    }

}

在图片浏览的Activity中获取需要显示的图片和设置ViewPager的Adapter

//获取data
Intent intent = view.getDataIntent();
images = intent.getStringArrayListExtra("images");
position = intent.getIntExtra("position",0);
view.setImageBrowse(images,position);
//设置ViewPager
adapter = new ViewPageAdapter(this,images);
vp.setAdapter(adapter);
vp.setCurrentItem(position);
vp.addOnPageChangeListener(this);
hint.setText(position + 1 + "/" + images.size());

监听ViewPager的滑动事件，设置hint的显示

@Override
public void onPageSelected(int position) {
    presenter.setPosition(position);
    hint.setText(position + 1 + "/" + presenter.getImages().size());
}

加入保存功能

Picasso.with(view.getMyContext()).load(imageUrl).into(new Target() {
    @Override
    public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
        // 创建目录
        File appDir = new File(Environment.getExternalStorageDirectory(), "JellyImage");
        if (!appDir.exists()) {
            appDir.mkdir();
        }

        String imageType = getImageType(imageUrl); //获取图片类型
        String fileName = System.currentTimeMillis() + "." + imageType;
        File file = new File(appDir, fileName);
        //保存图片
        try {
            FileOutputStream fos = new FileOutputStream(file);
            if(TextUtils.equals(imageType,"jpg")) imageType = "jpeg";
            imageType = imageType.toUpperCase();
            bitmap.compress(Bitmap.CompressFormat.valueOf(imageType), 100, fos);
            fos.flush();
            fos.close();
            Toast.makeText(view.getMyContext(),"保存成功",Toast.LENGTH_SHORT).show(); //Toast
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 其次把文件插入到系统图库
        try {
            MediaStore.Images.Media.insertImage(view.getMyContext().getContentResolver(), file.getAbsolutePath(), fileName, null);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        // 最后通知图库更新
        view.getMyContext().sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + file.getPath())));
    }

    @Override
    public void onBitmapFailed(Drawable errorDrawable) {

    }

    @Override
    public void onPrepareLoad(Drawable placeHolderDrawable) {

    }
});

到这里图片浏览器的功能就实现，效果图：

放大之前.png

放大后.png

完整代码：Mango