Android 使用Picasso加載網絡圖片等比例縮放

轉自：http://blog.csdn.net/picasso_l/article/details/50679177

最近做項目，要下載圖片到本地（不是指緩存），之前用過HttpURLConnection和HttpCLient，但是感覺太繁瑣，而且6.0之後到Apache包也不支持了，後來我想到了Picasso的緩存，Picasso緩存圖片，那肯定是下載到本地實現了，我們只要更改下本地路徑，就能輕鬆實現了。

廢話不多說，直接上代碼了。

private void download() {
        //獲得圖片的地址
        String url = mList.get(mPosition);

        //Target
        Target target = new Target(){

            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                String imageName = System.currentTimeMillis() + ".png";

                File dcimFile = FileUtil
                        .getDCIMFile(FileUtil.PATH_PHOTOGRAPH,imageName);

                LogCat.i("bitmap="+bitmap);
                FileOutputStream ostream = null;
                try {
                    ostream = new FileOutputStream(dcimFile);
                    bitmap.compress(Bitmap.CompressFormat.PNG, 100, ostream);
                    ostream.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }


                Toast.makeText(PicActivity.this,"圖片下載至:"+dcimFile,Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {

            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {

            }
        };

        //Picasso下載
        Picasso.with(this).load(url).into(target);

    }

應網友要求，貼出FileUtil代碼：


public class FileUtil {
    /**
     * 拍照路徑
     */

    private static String FILE_NAME = "userIcon.jpg";
    public static String PATH_PHOTOGRAPH = "/LXT/";

    private static boolean isExternalStorageWritable() {
        String state = Environment.getExternalStorageState();
        return Environment.MEDIA_MOUNTED.equals(state);
    }

    public static File getAvailableCacheDir() {
        if (isExternalStorageWritable()) {
            return App.app.getExternalCacheDir();
        } else {
            return App.app.getCacheDir();
        }
    }

    public static String getAvatarCropPath() {
        return new File(getAvailableCacheDir(), FILE_NAME).getAbsolutePath();
    }

    public static String getPublishPath(String fileName) {
        return new File(getAvailableCacheDir(), fileName).getAbsolutePath();
    }


    /**
     * 保存圖片
     *
     * @param bitmap
     * @param filePath
     */
    public static void saveBitmap(Bitmap bitmap, String filePath) {
        FileOutputStream bos = null;
        File file = new File(filePath);
        if (!file.getParentFile().exists()) {
            file.getParentFile().mkdirs();
        }
        try {
            bos = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            try {
                bos.flush();
                bos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


    public static void deleteDir(File directory) {
        if (directory != null){
            if (directory.isFile()) {
                directory.delete();
                return;
            }

            if (directory.isDirectory()) {
                File[] childFiles = directory.listFiles();
                if (childFiles == null || childFiles.length == 0) {
                    directory.delete();
                    return;
                }

                for (int i = 0; i < childFiles.length; i++) {
                    deleteDir(childFiles[i]);
                }
                directory.delete();
            }
        }
    }



    public static File getDCIMFile(String filePath, String imageName) {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) { // 文件可用
            File dirs = new File(Environment.getExternalStorageDirectory(),
                    "DCIM"+filePath);
            if (!dirs.exists())
                dirs.mkdirs();

            File file = new File(Environment.getExternalStorageDirectory(),
                    "DCIM"+filePath+imageName);
            if (!file.exists()) {
                try {
                    //在指定的文件夾中創建文件
                    file.createNewFile();
                } catch (Exception e) {
                }
            }
            return file;
        } else {
            return null;
        }

    }



    public static File saveBitmap2(Bitmap bitmap, String fileName, File baseFile) {
        FileOutputStream bos = null;
        File imgFile = new File(baseFile, "/" + fileName);
        try {
            bos = new FileOutputStream(imgFile);
            bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            try {
                bos.flush();
                bos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return imgFile;
    }

    public static File getBaseFile(String filePath) {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) { // 文件可用
            File f = new File(Environment.getExternalStorageDirectory(),
                    filePath);
            if (!f.exists())
                f.mkdirs();
            return f;
        } else {
            return null;
        }
    }

    public static String getFileName() {
        String fileName = FILE_NAME ;
        return fileName;
    }

    /**
     * 由指定的路徑和文件名創建文件
     */
    public static File createFile(String path, String name) throws IOException {
        File folder = new File(path);
        if (!folder.exists()) {
            folder.mkdirs();
        }
        File file = new File(path + name);
        if (!file.exists()) {
            file.createNewFile();
        }
        return file;
    }

}

這樣就輕鬆實現了，值得注意的是，我們經常用的是into（ImageView target），其實into還能傳入很多不同的對象。今天有點晚了，先寫到這，關於Picasso，還是有很多技巧可以探索的。之前還寫過一篇Android 使用Picasso加載網絡圖片等比例縮放的文章，也歡迎大家有空去指點一下。

參考文獻：
http://stackoverflow.com/questions/27729976/download-and-save-images-using-picasso