图片缓存框架Picasso的学习和使用

16-09-08 来源：[db:作者]

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搞Android的都知道对图片的下载和缓存处理非常的麻烦至极，动不动就发生OOM之类的情况。特别是在Listview，GridView，ViewPage等控件里面。至此介绍Picasso图片缓存框架使用。相对ImageLoad等框架更为方便快速开发者使用。介绍下Picasso;

Picasso是Square公司开源的一个Android图形缓存库，地址http://square.github.io/picasso/，可以实现图片下载和缓存功能。仅仅只需要一行代码就能完全实现图片的异步加载。

Picasso.with(context).load("../../DvpvklR.png").into(imageView);

Picasso不仅实现了图片异步加载的功能，还解决了android中加载图片时需要解决的一些常见问题：

1.在adapter中需要取消已经不在视野范围的ImageView图片资源的加载，否则会导致图片错位，Picasso已经解决了这个问题。

2.使用复杂的图片压缩转换来尽可能的减少内存消耗

3.自带内存和硬盘二级缓存功能。

下面分别附上Eclipse的使用JAR包和Android Studio使用的gradle

jar包地址：http://download.csdn.net/detail/ae_fring/9624010

Studio：compile 'com.squareup.picasso:picasso:2.5.2'

代码部分我就分享使用studio写的：使用ListView展示访问网络图片并且缓存起来使用。

请求网络数据我使用了xutils3.3.36。

Studio：compile 'org.xutils:xutils:3.3.36'

MainActivity页面

@ContentView(R.layout.activity_main)
public class MainActivity extends Activity {

    @ViewInject(R.id.lv)
    private ListView lv;

    private PicassoAdapter adapter;
    @ViewInject(R.id.cache_tv)
    private TextView cache_tv;
    /**
     * 获取数据的接口
     */
    private String[] data = {
            "http://img3.redocn.com/20101213/20101211_0e830c2124ac3d92718fXrUdsYf49nDl.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383291_6518.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383291_8239.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383290_9329.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383290_1042.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383275_3977.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383265_8550.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383264_3954.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383264_4787.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383264_8243.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383248_3693.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383243_5120.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383242_3127.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383242_9576.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383242_1721.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383219_5806.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383214_7794.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383213_4418.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383213_3557.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383210_8779.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383172_4577.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383166_3407.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383166_2224.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383166_7301.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383165_7197.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383150_8410.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383131_3736.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383130_5094.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383130_7393.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383129_8813.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383100_3554.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383093_7894.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383092_2432.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383092_3071.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383091_3119.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383059_6589.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383059_8814.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383059_2237.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383058_4330.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383038_3602.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382942_3079.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382942_8125.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382942_4881.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382941_4559.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382941_3845.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382924_8955.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382923_2141.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382923_8437.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382922_6166.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382922_4843.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382905_5804.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382904_3362.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382904_2312.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382904_4960.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382900_2418.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382881_4490.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382881_5935.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382880_3865.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382880_4662.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382879_2553.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382862_5375.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382862_1748.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382861_7618.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382861_8606.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382861_8949.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382841_9821.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382840_6603.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382840_2405.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382840_6354.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382839_5779.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382810_7578.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382810_2436.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382809_3883.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382809_6269.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382808_4179.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382790_8326.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382789_7174.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382789_5170.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382789_4118.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382788_9532.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382767_3184.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382767_4772.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382766_4924.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382766_5762.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406382765_7341.jpg"
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        x.view().inject(this);
        adapter = new PicassoAdapter(MainActivity.this, data);
        lv.setAdapter(adapter);
        lv.setOnScrollListener(onScrollListener);
        cache_tv.setText(CacheClearUtilManager.getTotalCacheSize(MainActivity.this));
        cache_tv.setOnClickListener(onclicklistener);


    }

    private View.OnClickListener onclicklistener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            CacheClearUtilManager.clearPicassoAllCache(MainActivity.this);
            cache_tv.setText(CacheClearUtilManager.getTotalCacheSize(MainActivity.this));
        }
    };

    private AbsListView.OnScrollListener onScrollListener = new AbsListView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            final Picasso picasso = Picasso.with(MainActivity.this);
            if (scrollState == SCROLL_STATE_IDLE || scrollState == SCROLL_STATE_TOUCH_SCROLL) {
                picasso.resumeTag(MainActivity.this);
            } else {
                picasso.pauseTag(MainActivity.this);
            }
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

        }
    };
}

至于Picasso我进行了一个简单的封装便于使用：

**
 * Created by zqf on 2016/8/8.
 */
public class PicassoUtil {


    /**
     * 加载指定宽高的图片
     *
     * @param context
     * @param path
     * @param width
     * @param height
     * @param imageView
     */
    public static void loadImageWithSize(Context context, String path, int width, int height, int placeholderresId, int errorResId, ImageView imageView) {
        Picasso.with(context).load(path).resize(width, height).centerCrop().placeholder(placeholderresId).error(errorResId).into(imageView);
    }

    public static void loadImageWithHodler(Context context, String path, int resId, ImageView imageView) {
        Picasso.with(context).load(path).fit().placeholder(resId).into(imageView);
    }

    public static void loadImageWithCrop(Context context, String path, ImageView imageView) {
        Picasso.with(context).load(path).transform(new CustomImageCrop()).into(imageView);
    }

    /**
     * 实现自定义图片裁剪
     */
    private static class CustomImageCrop implements Transformation {

        @Override
        public Bitmap transform(Bitmap source) {
            int size = Math.min(source.getWidth(), source.getHeight());
            int x = (source.getWidth() - size) / 2;
            int y = (source.getHeight() - size) / 2;
            Bitmap result = Bitmap.createBitmap(source, x, y, size, size);
            if (result == null) {
                result.recycle();
            }
            return result;
        }

        @Override
        public String key() {
            return "square()";
        }
    }
}

适配器页面：

/**
 * Created by zqf on 2016/8/7.
 */
public class PicassoAdapter extends BaseAdapter {

    private LayoutInflater inflater;
    private String[] data;
    private Context context;

    public PicassoAdapter(Context context, String[] data) {
        this.data = data;
        this.inflater = LayoutInflater.from(context);
        this.context = context;
    }

    @Override
    public int getCount() {
        return data.length;
    }

    @Override
    public Object getItem(int position) {
        return data[position];
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.item, null);
            holder = new ViewHolder();
            holder.iv = (ImageView) convertView.findViewById(R.id.iv);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        PicassoUtil.loadImageWithSize(context, data[position], 100, 100, R.mipmap.ic_launcher, R.mipmap.ic_launcher, holder.iv);

        return convertView;
    }

    private class ViewHolder {
        ImageView iv;
    }
}

是不是感觉到了非常简单，就几行代码完全搞定了。访问起来流畅并不会出现卡顿现象。如果觉得想试试赶紧试试吧！

当然了有写的不好的各位见谅，欢迎指出。

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