我正在使用以下方法从 url 下载单个图像
public static Bitmap getBitmap(String url) {
try {
InputStream is = (InputStream) new URL(url).getContent();
Bitmap d = BitmapFactory.decodeStream(is);
is.close();
return d;
} catch (Exception e) {
return null;
}
}
有时我会遇到内存不足异常。
我无法捕获内存不足异常。该应用程序将关闭。如何防止这种情况？
有没有更好的下载图像的方法也更快？
尝试使用这个：
public Bitmap getBitmapFromURL(String src) {
try {
java.net.URL url = new java.net.URL(src);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
对于 OutOfMemory 问题：
public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
int width = bm.getWidth();
int height = bm.getHeight();
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
// CREATE A MATRIX FOR THE MANIPULATION
Matrix matrix = new Matrix();
// RESIZE THE BIT MAP
matrix.postScale(scaleWidth, scaleHeight);
// "RECREATE" THE NEW BITMAP
Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height,
matrix, false);
return resizedBitmap;
}
public void DownloadImageFromPath(String path){
InputStream in =null;
Bitmap bmp=null;
ImageView iv = (ImageView)findViewById(R.id.img1);
int responseCode = -1;
try{
URL url = new URL(path);//"http://192.xx.xx.xx/mypath/img1.jpg
HttpURLConnection con = (HttpURLConnection)url.openConnection();
con.setDoInput(true);
con.connect();
responseCode = con.getResponseCode();
if(responseCode == HttpURLConnection.HTTP_OK)
{
//download
in = con.getInputStream();
bmp = BitmapFactory.decodeStream(in);
in.close();
iv.setImageBitmap(bmp);
}
}
catch(Exception ex){
Log.e("Exception",ex.toString());
}
}
将此 Android 网络依赖项添加到您的项目中
编译'com.amitshekhar.android:android-networking:1.0.0'
String url = "http://ichef.bbci.co.uk/onesport/cps/480/cpsprodpb/11136/production/_95324996_defoe_rex.jpg";
File file;
String dirPath, fileName;
Button downldImg;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialization Of DownLoad Button
downldImg = (Button) findViewById(R.id.DownloadButton);
// Initialization Of DownLoad Button
AndroidNetworking.initialize(getApplicationContext());
//Folder Creating Into Phone Storage
dirPath = Environment.getExternalStorageDirectory() + "/Image";
fileName = "image.jpeg";
//file Creating With Folder & Fle Name
file = new File(dirPath, fileName);
//Click Listener For DownLoad Button
downldImg.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
AndroidNetworking.download(url, dirPath, fileName)
.build()
.startDownload(new DownloadListener() {
@Override
public void onDownloadComplete() {
Toast.makeText(MainActivity.this, "DownLoad Complete", Toast.LENGTH_SHORT).show();
}
@Override
public void onError(ANError anError) {
}
});
}
});
}
}
运行此代码后检查您的手机内存，您可以看到一个文件夹 -在此文件夹内检查图像 ，您会看到一个名为“image.jpeg”的图像文件
谢谢你 ！！！
您可以Asyn task
使用此类下载图像：
public class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {
private final WeakReference<ImageView> imageViewReference;
private final MemoryCache memoryCache;
private final BrandItem brandCatogiriesItem;
private Context context;
private String url;
public ImageDownloaderTask(ImageView imageView, String url, Context context) {
imageViewReference = new WeakReference<ImageView>(imageView);
memoryCache = new MemoryCache();
brandCatogiriesItem = new BrandItem();
this.url = url;
this.context = context;
}
@Override
protected Bitmap doInBackground(String... params) {
return downloadBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
if (isCancelled()) {
bitmap = null;
}
if (imageViewReference != null) {
ImageView imageView = imageViewReference.get();
if (imageView != null) {
if (bitmap != null) {
memoryCache.put("1", bitmap);
brandCatogiriesItem.setUrl(url);
brandCatogiriesItem.setThumb(bitmap);
// BrandCatogiriesItem.saveLocalBrandOrCatogiries(context, brandCatogiriesItem);
imageView.setImageBitmap(bitmap);
} else {
Drawable placeholder = imageView.getContext().getResources().getDrawable(R.drawable.placeholder);
imageView.setImageDrawable(placeholder);
}
}
}
}
private Bitmap downloadBitmap(String url) {
HttpURLConnection urlConnection = null;
try {
URL uri = new URL(url);
urlConnection = (HttpURLConnection) uri.openConnection();
int statusCode = urlConnection.getResponseCode();
if (statusCode != HttpStatus.SC_OK) {
return null;
}
InputStream inputStream = urlConnection.getInputStream();
if (inputStream != null) {
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
}
} catch (Exception e) {
Log.d("URLCONNECTIONERROR", e.toString());
if (urlConnection != null) {
urlConnection.disconnect();
}
Log.w("ImageDownloader", "Error downloading image from " + url);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return null;
}
}
并称其为：
new ImageDownloaderTask(thumbImage, item.thumbnail, context).execute(item.thumbnail);
第 1 步：在 Android 清单中声明权限
在您的第一个 Android 项目中要做的第一件事是在“AndroidManifest.xml”文件中声明所需的权限。
对于 Android 从 URL 下载图像，我们需要访问 Internet 以下载文件并读取和写入内部存储以将图像保存到内部存储的权限。
在 AndroidManifest.xml 文件的标签顶部添加以下代码行：
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
第 2 步：向用户请求所需的权限
Android 允许每个应用程序在沙盒中运行。如果应用程序需要访问该沙箱之外的某些资源或信息，则需要向用户请求许可。
从 Android 6.0 开始，谷歌希望开发人员在应用程序内向用户请求权限，有关权限的更多详细信息请阅读此内容。
因此，对于 Android 从 URL 下载图像，您需要请求读取存储和写入
为此，我们将使用以下代码行首先检查用户是否已授予所需的权限，如果没有，则我们将请求存储读写权限的权限。
我们正在创建一个方法“Downlaod Image”，您可以在需要下载图像的任何地方简单地调用它。
void DownloadImage(String ImageUrl) {
if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED &&
ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 123);
ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 123);
showToast("Need Permission to access storage for Downloading Image");
} else {
showToast("Downloading Image...");
//Asynctask to create a thread to downlaod image in the background
new DownloadsImage().execute(ImageUrl);
}
}
现在我们已经请求并被授予用户权限，从 url 开始下载 android 图像，我们将创建一个 AsyncTask，因为您不允许在主线程中运行后台进程。
class DownloadsImage extends AsyncTask<String, Void,Void>{
@Override
protected Void doInBackground(String... strings) {
URL url = null;
try {
url = new URL(strings[0]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
Bitmap bm = null;
try {
bm = BitmapFactory.decodeStream(url.openConnection().getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
//Create Path to save Image
File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES+ "/AndroidDvlpr"); //Creates app specific folder
if(!path.exists()) {
path.mkdirs();
}
File imageFile = new File(path, String.valueOf(System.currentTimeMillis())+".png"); // Imagename.png
FileOutputStream out = null;
try {
out = new FileOutputStream(imageFile);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try{
bm.compress(Bitmap.CompressFormat.PNG, 100, out); // Compress Image
out.flush();
out.close();
// Tell the media scanner about the new file so that it is
// immediately available to the user.
MediaScannerConnection.scanFile(MainActivity.this,new String[] { imageFile.getAbsolutePath() }, null,new MediaScannerConnection.OnScanCompletedListener() {
public void onScanCompleted(String path, Uri uri) {
// Log.i("ExternalStorage", "Scanned " + path + ":");
// Log.i("ExternalStorage", "-> uri=" + uri);
}
});
} catch(Exception e) {
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
showToast("Image Saved!");
}
}
在上面给出的代码行中，创建了一个 URL 和位图，使用 BitmapFactory.decodeStream 下载文件。
创建文件路径以保存图像（我们在 DIRECTORY_PICTURES 中创建了一个名为“AndroidDvlpr”的文件夹）并初始化下载。
下载文件 MediaScannerConnection 后，将调用从文件中读取元数据并将文件添加到媒体内容提供程序，以便用户可以使用图像。
在上面的代码行中，我们还创建了一个方法 showToast() 来显示 Toast。完整代码在这里：
void showToast(String msg){
Toast.makeText(MainActivity.this,msg,Toast.LENGTH_SHORT).show();
}
按照官方指南加载大位图可以避免 OOM 异常。
不要在 UI 线程上运行您的代码。改用AsyncTask应该没问题。
您可以使用以下功能从 url 下载图像。
private Bitmap getImage(String imageUrl, int desiredWidth, int desiredHeight)
{
private Bitmap image = null;
int inSampleSize = 0;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
options.inSampleSize = inSampleSize;
try
{
URL url = new URL(imageUrl);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
InputStream stream = connection.getInputStream();
image = BitmapFactory.decodeStream(stream, null, options);
int imageWidth = options.outWidth;
int imageHeight = options.outHeight;
if(imageWidth > desiredWidth || imageHeight > desiredHeight)
{
System.out.println("imageWidth:"+imageWidth+", imageHeight:"+imageHeight);
inSampleSize = inSampleSize + 2;
getImage(imageUrl);
}
else
{
options.inJustDecodeBounds = false;
connection = (HttpURLConnection)url.openConnection();
stream = connection.getInputStream();
image = BitmapFactory.decodeStream(stream, null, options);
return image;
}
}
catch(Exception e)
{
Log.e("getImage", e.toString());
}
return image;
}
在此处查看完整说明
我建议使用 altex-image-downloader 库，它可以轻松下载图像：
AltexImageDownloader.writeToDisk(context, Imageurl, "IMAGES");
在 app build gradle 中添加依赖：
implementation 'com.artjimlop:altex-image-downloader:0.0.4'
我仍在学习 Android，所以我无法为我的建议提供丰富的上下文或理由，但这是我用来从 https 和本地 url 检索文件的方法。我在我的 onActivity 结果中使用它（用于拍照和从图库中选择），以及在 AsyncTask 中检索 https url。
InputStream input = new URL("your_url_string").openStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
在 Android Manifest 中首先声明权限：-
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
MainActivityForDownloadImages.java
public class MainActivityForDownloadImages extends AppCompatActivity {
// String urls = "https://stimg.cardekho.com/images/carexteriorimages/930x620/Kia/Kia-Seltos/6232/1562746799300/front-left-side-47.jpg";
String urls = "https://images5.alphacoders.com/609/609173.jpg";
Button button;
public final Context context = this;
ProgressDialog progressDialog ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_for_download_images);
if (ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE}, 0);
}
progressDialog = new ProgressDialog(context);
button = findViewById(R.id.downloadImagebtn);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// initialize the progress dialog like in the first example
// this is how you fire the downloader
Intent intent = new Intent(context, DownloadService.class);
intent.putExtra("url", urls);
intent.putExtra("receiver", new DownloadReceiver(new Handler()));
startService(intent);
}
});
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
if (requestCode == 0) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED
&& grantResults[1] == PackageManager.PERMISSION_GRANTED) {
}
}
}
private class DownloadReceiver extends ResultReceiver {
public DownloadReceiver(Handler handler) {
super(handler);
}
@Override
protected void onReceiveResult(int resultCode, Bundle resultData) {
super.onReceiveResult(resultCode, resultData);
if (resultCode == DownloadService.UPDATE_PROGRESS) {
int progress = resultData.getInt("progress"); //get the progress
progressDialog.setProgress(progress);
progressDialog.setMessage("Images Is Downloading");
progressDialog.show();
if (progress == 100) {
progressDialog.dismiss();
}
}
}
}
}
下载服务.java
public class DownloadService extends IntentService {
public static final int UPDATE_PROGRESS = 8344;
String folder_main = "ImagesFolder";
public DownloadService() {
super("DownloadService");
}
@Override
protected void onHandleIntent(Intent intent) {
String urlToDownload = intent.getStringExtra("url");
ResultReceiver receiver = (ResultReceiver) intent.getParcelableExtra("receiver");
try {
//create url and connect
URL url = new URL(urlToDownload);
URLConnection connection = url.openConnection();
connection.connect();
// this will be useful so that you can show a typical 0-100% progress bar
int fileLength = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(connection.getInputStream());
File outerFolder = new File(Environment.getExternalStorageDirectory(), folder_main);
File inerDire = new File(outerFolder.getAbsoluteFile(), System.currentTimeMillis() + ".jpg");
if (!outerFolder.exists()) {
outerFolder.mkdirs();
}
inerDire.createNewFile();
FileOutputStream output = new FileOutputStream(inerDire);
byte data[] = new byte[1024];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
Bundle resultData = new Bundle();
resultData.putInt("progress", (int) (total * 100 / fileLength));
receiver.send(UPDATE_PROGRESS, resultData);
output.write(data, 0, count);
}
// close streams
output.flush();
output.close();
input.close();
} catch (IOException e) {
e.printStackTrace();
}
Bundle resultData = new Bundle();
resultData.putInt("progress", 100);
receiver.send(UPDATE_PROGRESS, resultData);
}
}
public class testCrop extends AppCompatActivity {
ImageView iv;
String imagePath = "https://style.pk/wp-content/uploads/2015/07/omer-Shahzad-performed-umrah-600x548.jpg";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.testcrpop);
iv = (ImageView) findViewById(R.id.testCrop);
imageDownload image = new imageDownload(testCrop.this, iv);
image.execute(imagePath);
}
class imageDownload extends AsyncTask<String, Integer, Bitmap> {
Context context;
ImageView imageView;
Bitmap bitmap;
InputStream in = null;
int responseCode = -1;
//constructor.
public imageDownload(Context context, ImageView imageView) {
this.context = context;
this.imageView = imageView;
}
@Override
protected void onPreExecute() {
}
@Override
protected Bitmap doInBackground(String... params) {
URL url = null;
try {
url = new URL(params[0]);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setDoOutput(true);
httpURLConnection.connect();
responseCode = httpURLConnection.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
in = httpURLConnection.getInputStream();
bitmap = BitmapFactory.decodeStream(in);
in.close();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap data) {
imageView.setImageBitmap(data);
}
}
}
输出
您可以使用此功能将您的位图/图像保存在所有 android 版本（包括 Android 11）的图库中
private fun addImageToGallery(fileName: String, bitmap: Bitmap, ctx: Context) {
try {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
val fos: OutputStream
val resolver = contentResolver
val values = ContentValues()
values.put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
values.put(MediaStore.MediaColumns.MIME_TYPE, "image/jpeg")
values.put(
MediaStore.MediaColumns.RELATIVE_PATH,
Environment.DIRECTORY_PICTURES + File.separator + "EduImages"
)
val imageUri = resolver.insert(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
values
)
fos = resolver.openOutputStream(imageUri!!) as OutputStream
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos)
fos.close()
Toast.makeText(
ctx, "Saved in gallery",
Toast.LENGTH_SHORT
).show()
} else {
val values = ContentValues()
values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg")
values.put(MediaStore.Images.ImageColumns.DISPLAY_NAME, fileName)
values.put(MediaStore.Images.ImageColumns.TITLE, fileName)
val uri: Uri? = ctx.contentResolver.insert(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
values
)
uri?.let {
ctx.contentResolver.openOutputStream(uri)?.let { stream ->
val oStream =
BufferedOutputStream(stream)
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, oStream)
oStream.close()
Toast.makeText(ctx, "Saved in gallery", Toast.LENGTH_SHORT)
.show()
}
}
}
} catch (e: Exception) {
Toast.makeText(ctx, e.localizedMessage, Toast.LENGTH_SHORT).show()
}
}
尝试使用以下代码从 Android 上的 URL 下载图像：
DownloadManager downloadManager = (DownloadManager)getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse(imageName);
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
Long reference = downloadManager.enqueue(request);