Question

我是Android和Java的新手。我一直致力于我的任务，即Image Downloader。我必须使用进度条下载图像并在网格视图中显示它们。我创建了两个类1. URLImageAdapter 2. CacheActivity。一切正常但现在我想将这些图像保存到SD卡。我一直在寻找应该采用哪些方法和更改？有帮助吗？谢谢。 我已在Android清单文件中添加了权限。

public class URLImageAdapter extends BaseAdapter {

private class Image {
    String url;
    Bitmap thumb;
}

private Image[] images;
private Context myContext;
public LoadThumbsTask thumbnailGen;
private Object previousList;


public URLImageAdapter(Context c) {
    myContext = c;
    thumbnailGen = new LoadThumbsTask();

    if (previousList != null) {
        images = (Image[]) previousList;
        thumbnailGen.execute(images);
        return;
    }

    images = new Image[imageURLs.length];

    for (int i = 0, j = imageURLs.length; i < j; i++) {
        images[i] = new Image();
        images[i].url = imageURLs[i];
    }

    thumbnailGen.execute(images);

}

public int getCount() {
    return images.length;
}

public Object getItem(int position) {
    return images[position].url;
}

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

public Object getData() {
    if (thumbnailGen != null
            && thumbnailGen.getStatus() != AsyncTask.Status.FINISHED) {
        thumbnailGen.cancel(true);
    }

    return images;
}

public View getView(int position, View convertView, ViewGroup parent) {

    ImageView imgView;

    Image cached = images[position];

    if (convertView == null) {

        imgView = new ImageView(myContext);
        imgView.setLayoutParams(new GridView.LayoutParams(100, 100));

    } else {

        imgView = (ImageView) convertView;

    }

    if (cached.thumb == null) {

        imgView.setImageResource(R.drawable.ic_action_search);
        imgView.setScaleType(ScaleType.CENTER);

    } else {

        imgView.setScaleType(ScaleType.FIT_CENTER);
        imgView.setImageBitmap(cached.thumb);

    }

    return imgView;
}

private void cacheUpdated() {
    this.notifyDataSetChanged();
}


private Bitmap loadThumb(String url) {

    Bitmap thumb = null;

    BitmapFactory.Options opts = new BitmapFactory.Options();
    opts.inSampleSize = 4;

    try {

        URL u = new URL(url);
        URLConnection c = u.openConnection();
        c.connect();

        BufferedInputStream stream = new BufferedInputStream(
                c.getInputStream());

        thumb = BitmapFactory.decodeStream(stream, null, opts);


        stream.close();

    } catch (MalformedURLException e) {
        Log.e("ERROR", "malformed url: " + url);
    } catch (IOException e) {
        Log.e("ERROR", "An error has occurred downloading the image: "
                + url);
    }

    return thumb;
}

private class LoadThumbsTask extends AsyncTask<Image, Void, Void> {

    /*private ProgressDialog dialog;
      @Override
        protected void onPreExecute() {
        this.dialog = ProgressDialog.show(myContext, "Please wait",
            "Downloading.....", true);
                }

            @Override
            protected void onPostExecute(Void unused) {
    //Intent for next activity
     this.dialog.dismiss();
    }*/

    @Override
    protected Void doInBackground(Image... cache) {

        BitmapFactory.Options opts = new BitmapFactory.Options();
        opts.inSampleSize = 4;

        for (Image i : cache) {

            if (isCancelled())
                return null;

            if (i.thumb != null)
                continue;

            SystemClock.sleep(500);

            i.thumb = loadThumb(i.url);

            publishProgress();
        }

        return null;

    }

    @Override
    protected void onProgressUpdate(Void... param) {
        cacheUpdated();
    }
}

private String[] imageURLs = {
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2851.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2944.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2989.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3005.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3012.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3034.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3047.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3092.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3110.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3113.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3128.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3160.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3226.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3228.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3251.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3268.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3275.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3346.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3365.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3374.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3385.jpg",
        "http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3392.jpg", };
 }

CacheActivity

public class CacheActivity extends Activity {

Button btnStartProgress;
ProgressDialog progressBar;
private int progressBarStatus = 0;
private Handler progressBarHandler = new Handler();
private GridView gridview;
private long fileSize = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cache);
     gridview = (GridView) findViewById(R.id.grid_view);
     addListenerOnButton();
}




public void addListenerOnButton() {

    btnStartProgress = (Button) findViewById(R.id.btnStartProgress);
    btnStartProgress.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {

            progressBar = new ProgressDialog(v.getContext());
            progressBar.setCancelable(true);
            progressBar.setMessage("File downloading ...");
            progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            progressBar.setProgress(0);
            progressBar.setMax(100);
            progressBar.show();

            progressBarStatus = 0;

            fileSize = 0;

            new Thread(new Runnable() {
                public void run() {
                    while (progressBarStatus < 100) {

                        progressBarStatus = doInBackground();


                        try {
                            Thread.sleep(7500);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        progressBarHandler.post(new Runnable() {
                            public void run() {
                                progressBar.setProgress(progressBarStatus);
                            }
                        });
                    }

                    if (progressBarStatus >= 100) {

                        try {
                            Thread.sleep(450);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        progressBar.dismiss();

                    }
                }
            }).start();
            try {
                gridview.setAdapter(new URLImageAdapter(CacheActivity.this));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    });

}

public int doInBackground() {

    while (fileSize <= 1000000) {

        fileSize++;

        if (fileSize == 100000) {
            return 10;
        } else if (fileSize == 200000) {
            return 20;
        } else if (fileSize == 300000) {
            return 30;
        }else if (fileSize == 400000) {
            return 40;
        }else if (fileSize == 500000) {
            return 50;
        }else if (fileSize == 600000) {
            return 60;
        }else if (fileSize == 700000) {
            return 70;
        }else if (fileSize == 800000) {
            return 80;
        }else if (fileSize == 900000) {
            return 90;
        }

    }

    return 100;

}

 }

Answer 1

在

下的getView（）中调用以下方法

        imgView.setScaleType(ScaleType.FIT_CENTER);
        imgView.setImageBitmap(cached.thumb);
        saveDataInSdCard(cached.thumb,position);


private void saveDataInSdCard(Bitmap bt,int i) {
    OutputStream fOut = null;
    Uri outputFileUri;
    try {
        File root = new File(Environment.getExternalStorageDirectory()
                + File.separator + "urFlodername" + File.separator);
        root.mkdirs();
        sdImageMainDirectory = new File(root,i+"myPicName.jpg");
        outputFileUri = Uri.fromFile(sdImageMainDirectory);
        fOut = new FileOutputStream(sdImageMainDirectory);
    } catch (Exception e) {

    }

    Bitmap bm =bt;
    try {
        bm.compress(Bitmap.CompressFormat.PNG, 100, fOut);
        fOut.flush();
        fOut.close();
    } catch (Exception e) {
    }       

}



 add permission    
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Answer 2

基本上，您已将下载的图像加载到位图中。所以你的大部分工作都是完整的。接下来你需要做的是

OutputStream fout = null;
                File file = new File(name);
                try {
                    fout = new FileOutputStream(file);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
                thumb.compress(Bitmap.CompressFormat.JPEG, 100, fout);
                try {
                    fout.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    fout.close();
                }

Answer 3

http://negativeprobability.blogspot.in/2011/08/lazy-loading-of-images-in-listview.html

imagecursor = managedQuery(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, img, null,null, MediaStore.Images.Thumbnails.IMAGE_ID + "");

以上链接可帮助您在代码中进行更好的更改。常见的情况是将图像添加到Listview。例如，如果你正在制作一个鸡尾酒食谱应用程序，你会想要鸡尾酒名称旁边的图片。有时，应从互联网上检索图像，然后进行显示。不幸的是，这很难做到。如果你已经尝试过，你可能已经注意到性能命中或者一些奇怪的故障。在本教程中，我将向您展示如何下载图像并显示它们。我们还将讨论一些陷阱，如回收和并发。

Android将多个图像保存到SD卡

3 个答案: