Java 从Internet获取图像并设置为ImageView
我有一个名为tab1的ImageView。我的代码看起来像这样Java 从Internet获取图像并设置为ImageView,java,android,url,imageview,Java,Android,Url,Imageview,我有一个名为tab1的ImageView。我的代码看起来像这样 import java.io.InputStream; import java.net.URL; import android.app.Activity; import android.graphics.drawable.Drawable; import android.os.Bundle; import android.widget.ImageView; import android.widget.TabHost; import
import java.io.InputStream;
import java.net.URL;
import android.app.Activity;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TabHost;
import android.widget.Toast;
public class Paikallissaa extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TabHost tabs = (TabHost) findViewById(R.id.tabhost);
tabs.setup();
TabHost.TabSpec spec = tabs.newTabSpec("tag1");
try {
ImageView iv = (ImageView) findViewById(R.id.tab1);
URL url = new URL("http://cdn.fmi.fi/weather-observations/products/finland/finland-weather-observations-map.png");
InputStream content = (InputStream) url.getContent();
Drawable d = Drawable.createFromStream(content, "src");
iv.setImageDrawable(d);
} catch (Exception e) {
Toast.makeText(this, "Error getting image: " + e, Toast.LENGTH_SHORT);
}
spec.setContent(R.id.tab1);
spec.setIndicator("Koko maa");
tabs.addTab(spec);
spec = tabs.newTabSpec("tag2");
spec.setContent(R.id.tab2);
spec.setIndicator("Raisio");
tabs.addTab(spec);
}
}
它不会更新图像。发生了什么？它一直显示我前面在main.xml中设置的图像 要从internet获取图像，请尝试以下操作：
HttpGet httpRequest = new HttpGet(URI.create("http://cdn.fmi.fi/weather-observations/products/finland/finland-weather-observations-map.png") );
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
HttpEntity entity = response.getEntity();
BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
bmp = BitmapFactory.decodeStream(bufHttpEntity.getContent());
ImageView iv = (ImageView) findViewById(R.id.tab1);
iv.setImageBitmat(bmp);
httpRequest.abort();
要从internet获取图像，请尝试以下操作：
HttpGet httpRequest = new HttpGet(URI.create("http://cdn.fmi.fi/weather-observations/products/finland/finland-weather-observations-map.png") );
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
HttpEntity entity = response.getEntity();
BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
bmp = BitmapFactory.decodeStream(bufHttpEntity.getContent());
ImageView iv = (ImageView) findViewById(R.id.tab1);
iv.setImageBitmat(bmp);
httpRequest.abort();
这将下载一个图像，并将其设置为图像视图，该视图取自我帮助编写的一个应用程序。我去掉了一些我正在使用的无用代码，但方法保持不变
public void setImage(){
imageView.setImageURI(DownloadImage);
}
public String DownloadImage(){
string filepath = DownloadFromUrl("url","filename.png");
}
public String DownloadFromUrl(String imageURL, String fileName) {
File file = new File(PATH + fileName);
try {
URL url = new URL(imageURL);
long startTime = System.currentTimeMillis();
Log.d("ImageManager", "download begining");
Log.d("ImageManager", "download url:" + url);
Log.d("ImageManager", "downloaded file name:" + fileName);
/* Open a connection to that URL. */
URLConnection ucon = url.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
/*
* Read bytes to the Buffer until there is nothing more to read(-1).
*/
ByteArrayBuffer baf = new ByteArrayBuffer(50);
int current = 0;
while ((current = bis.read()) != -1) {
baf.append((byte) current);
}
/* Convert the Bytes read to a String. */
FileOutputStream fos = new FileOutputStream(file);
fos.write(baf.toByteArray());
fos.close();
Log.d("ImageManager",
"download ready in"
+ ((System.currentTimeMillis() - startTime) / 1000)
+ " sec");
} catch (IOException e) {
Log.d("ImageManager", "Error: " + e);
}
return file.toString();
}这将下载一幅图像，并将其设置为图像视图，该视图取自我帮助编写的应用程序。我去掉了一些我正在使用的无用代码，但方法保持不变
public void setImage(){
imageView.setImageURI(DownloadImage);
}
public String DownloadImage(){
string filepath = DownloadFromUrl("url","filename.png");
}
public String DownloadFromUrl(String imageURL, String fileName) {
File file = new File(PATH + fileName);
try {
URL url = new URL(imageURL);
long startTime = System.currentTimeMillis();
Log.d("ImageManager", "download begining");
Log.d("ImageManager", "download url:" + url);
Log.d("ImageManager", "downloaded file name:" + fileName);
/* Open a connection to that URL. */
URLConnection ucon = url.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
/*
* Read bytes to the Buffer until there is nothing more to read(-1).
*/
ByteArrayBuffer baf = new ByteArrayBuffer(50);
int current = 0;
while ((current = bis.read()) != -1) {
baf.append((byte) current);
}
/* Convert the Bytes read to a String. */
FileOutputStream fos = new FileOutputStream(file);
fos.write(baf.toByteArray());
fos.close();
Log.d("ImageManager",
"download ready in"
+ ((System.currentTimeMillis() - startTime) / 1000)
+ " sec");
} catch (IOException e) {
Log.d("ImageManager", "Error: " + e);
}
return file.toString();
}为了做到这一点，我一直在使用一个助手类，我在互联网上找到了这个类，并对其进行了一些修改。它负责缓存图像并将图像加载到背景线程上 由于您的映像在服务器上发生了更改，您可能希望删除此代码的缓存部分 用法：
ImageLoader loader = new ImageLoader(this);
loader.DisplayImage(String.format(headshotUrl, data.Id), this, headshot);
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Stack;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.widget.ImageView;
public class ImageLoader
{
public static String TAG = "xxx";
// the simplest in-memory cache implementation. This should be replaced with
// something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
private HashMap<String, Bitmap> cache = new HashMap<String, Bitmap>();
private File cacheDir;
public ImageLoader(Context context)
{
photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);
cacheDir = Utilities.GetCacheDir(context);
}
final int stub_id = R.drawable.face_placeholder;
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
imageView.setTag(url);
Log.i(TAG, url);
if (cache.containsKey(url))
imageView.setImageBitmap(cache.get(url));
else
{
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
// This ImageView may be used for other images before. So there may be
// some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p = new PhotoToLoad(url, imageView);
synchronized (photosQueue.photosToLoad)
{
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
// start thread if it's not started yet
if (photoLoaderThread.getState() == Thread.State.NEW)
photoLoaderThread.start();
}
private Bitmap getBitmap(String url)
{
// I identify images by hashcode. Not a perfect solution, good for the
// demo.
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
// from SD cache
Bitmap b = decodeFile(f);
if (b != null)
return b;
// from web
try
{
Bitmap bitmap = null;
InputStream is = new URL(url).openStream();
OutputStream os = new FileOutputStream(f);
Utilities.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex)
{
ex.printStackTrace();
return null;
}
}
// decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f)
{
try
{
// decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
// Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE = 70;
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true)
{
if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE)
break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e)
{
e.printStackTrace();
}
return null;
}
// Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i)
{
url = u;
imageView = i;
}
}
PhotosQueue photosQueue = new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
// stores list of photos to download
class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad = new Stack<PhotoToLoad>();
// removes all instances of this ImageView
public void Clean(ImageView image)
{
for (int j = 0; j < photosToLoad.size();)
{
if (photosToLoad.get(j).imageView == image)
photosToLoad.remove(j);
else
++j;
}
};
}
class PhotosLoader extends Thread
{
public void run()
{
try
{
while (true)
{
// thread waits until there are any images to load in the
// queue
if (photosQueue.photosToLoad.size() == 0)
synchronized (photosQueue.photosToLoad)
{
photosQueue.photosToLoad.wait();
}
if (photosQueue.photosToLoad.size() != 0)
{
PhotoToLoad photoToLoad;
synchronized (photosQueue.photosToLoad)
{
photoToLoad = photosQueue.photosToLoad.pop();
}
Bitmap bmp = getBitmap(photoToLoad.url);
cache.put(photoToLoad.url, bmp);
Object tag = photoToLoad.imageView.getTag();
if (tag != null && ((String) tag).equals(photoToLoad.url))
{
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a = (Activity) photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if (Thread.interrupted())
break;
}
} catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
PhotosLoader photoLoaderThread = new PhotosLoader();
// Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i)
{
bitmap = b;
imageView = i;
}
public void run()
{
Log.i(TAG, "BitmapDisplayer run()");
if (bitmap != null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
public void clearCache()
{
// clear memory cache
cache.clear();
// clear SD cache
File[] files = cacheDir.listFiles();
for (File f : files)
f.delete();
}
}
public static void CopyStream(InputStream is, OutputStream os)
{
final int buffer_size = 1024;
try
{
byte[] bytes = new byte[buffer_size];
for (;;)
{
int count = is.read(bytes, 0, buffer_size);
if (count == -1)
break;
os.write(bytes, 0, count);
}
} catch (Exception ex)
{
}
}
为了做到这一点，我一直在使用一个助手类，我在互联网上找到了这个类，并对其进行了一些修改。它负责缓存图像并将图像加载到背景线程上 由于您的映像在服务器上发生了更改，您可能希望删除此代码的缓存部分 用法：
ImageLoader loader = new ImageLoader(this);
loader.DisplayImage(String.format(headshotUrl, data.Id), this, headshot);
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Stack;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.widget.ImageView;
public class ImageLoader
{
public static String TAG = "xxx";
// the simplest in-memory cache implementation. This should be replaced with
// something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
private HashMap<String, Bitmap> cache = new HashMap<String, Bitmap>();
private File cacheDir;
public ImageLoader(Context context)
{
photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);
cacheDir = Utilities.GetCacheDir(context);
}
final int stub_id = R.drawable.face_placeholder;
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
imageView.setTag(url);
Log.i(TAG, url);
if (cache.containsKey(url))
imageView.setImageBitmap(cache.get(url));
else
{
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
// This ImageView may be used for other images before. So there may be
// some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p = new PhotoToLoad(url, imageView);
synchronized (photosQueue.photosToLoad)
{
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
// start thread if it's not started yet
if (photoLoaderThread.getState() == Thread.State.NEW)
photoLoaderThread.start();
}
private Bitmap getBitmap(String url)
{
// I identify images by hashcode. Not a perfect solution, good for the
// demo.
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
// from SD cache
Bitmap b = decodeFile(f);
if (b != null)
return b;
// from web
try
{
Bitmap bitmap = null;
InputStream is = new URL(url).openStream();
OutputStream os = new FileOutputStream(f);
Utilities.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex)
{
ex.printStackTrace();
return null;
}
}
// decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f)
{
try
{
// decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
// Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE = 70;
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true)
{
if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE)
break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e)
{
e.printStackTrace();
}
return null;
}
// Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i)
{
url = u;
imageView = i;
}
}
PhotosQueue photosQueue = new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
// stores list of photos to download
class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad = new Stack<PhotoToLoad>();
// removes all instances of this ImageView
public void Clean(ImageView image)
{
for (int j = 0; j < photosToLoad.size();)
{
if (photosToLoad.get(j).imageView == image)
photosToLoad.remove(j);
else
++j;
}
};
}
class PhotosLoader extends Thread
{
public void run()
{
try
{
while (true)
{
// thread waits until there are any images to load in the
// queue
if (photosQueue.photosToLoad.size() == 0)
synchronized (photosQueue.photosToLoad)
{
photosQueue.photosToLoad.wait();
}
if (photosQueue.photosToLoad.size() != 0)
{
PhotoToLoad photoToLoad;
synchronized (photosQueue.photosToLoad)
{
photoToLoad = photosQueue.photosToLoad.pop();
}
Bitmap bmp = getBitmap(photoToLoad.url);
cache.put(photoToLoad.url, bmp);
Object tag = photoToLoad.imageView.getTag();
if (tag != null && ((String) tag).equals(photoToLoad.url))
{
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a = (Activity) photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if (Thread.interrupted())
break;
}
} catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
PhotosLoader photoLoaderThread = new PhotosLoader();
// Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i)
{
bitmap = b;
imageView = i;
}
public void run()
{
Log.i(TAG, "BitmapDisplayer run()");
if (bitmap != null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
public void clearCache()
{
// clear memory cache
cache.clear();
// clear SD cache
File[] files = cacheDir.listFiles();
for (File f : files)
f.delete();
}
}
public static void CopyStream(InputStream is, OutputStream os)
{
final int buffer_size = 1024;
try
{
byte[] bytes = new byte[buffer_size];
for (;;)
{
int count = is.read(bytes, 0, buffer_size);
if (count == -1)
break;
os.write(bytes, 0, count);
}
} catch (Exception ex)
{
}
}
最好的方法是先下载图像，保存它，然后将图像路径设置为图像视图。顺便问一下，您的日志中有哪些错误？图像大约每2-3次更改一次。下载多次好吗？或者你是什么意思？不，我没有任何错误。是的，如果你没有网络连接，你可以显示上次下载的图像。但是，这取决于您的用例。最好的方法是首先下载图像，保存它，然后将图像路径设置为图像视图。顺便问一下，您的日志中有哪些错误？图像大约每2-3次更改一次。下载多次好吗？或者你是什么意思？不，我没有任何错误。是的，如果你没有网络连接，你可以显示上次下载的图像。但是，这取决于您的用例。这可能有点复杂，但这可以防止UI线程被下载阻止，并允许在无法下载时使用占位符图像。您可以发布实用程序.CopyStream（InputStream，OutputStream）方法吗？我猜它与IOUtils.copy（）相同@Adam我添加了复制流方法。除了图像很小：）是预期的还是我弄糟了什么？这可能有点复杂，但这可以防止UI线程被下载阻止，并允许在无法下载时使用占位符图像。你能发布Utilities.CopyStream吗（InputStream，OutputStream）方法？我猜它与IOUtils.copy（）相同。Adam我添加了复制流方法。除了图像很小：）是预期的还是我弄糟了什么？