我有一個關于從網站加載圖像的問題。我使用的代碼是：Display display = getWindowManager().getDefaultDisplay(); int width = display.getWidth();int height = display.getHeight();Bitmap bit=null;try { bit = BitmapFactory.decodeStream((InputStream)new URL("http://www.mac-wallpapers.com/bulkupload/wallpapers/Apple%20Wallpapers/apple-black-logo-wallpaper.jpg").getContent());} catch (Exception e) {}Bitmap sc = Bitmap.createScaledBitmap(bit,width,height,true);canvas.drawBitmap(sc,0,0,null);但它總是返回一個空指針異常，程序崩潰了。該URL有效，似乎適用于其他所有人。我正在使用2.3.1。
3 回答
MMMHUHU
TA貢獻1834條經驗 獲得超8個贊
public static Bitmap getBitmapFromURL(String src) {
try {
URL url = new 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) {
// Log exception
return null;
}
}
POPMUISE
TA貢獻1765條經驗 獲得超5個贊
如果您使用Picasso或Glide或Universal-Image-Loader從網址加載圖像。
您可以簡單地獲取加載的位圖
畢加索 （當前版本2.71828）
Java代碼
Picasso.get().load(imageUrl).into(new Target() {
@Override
public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
// loaded bitmap is here (bitmap)
}
@Override
public void onBitmapFailed(Drawable errorDrawable) { }
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {}
});
Kotlin代碼
Picasso.get().load(url).into(object : com.squareup.picasso.Target {
override fun onBitmapLoaded(bitmap: Bitmap?, from: Picasso.LoadedFrom?) {
// loaded bitmap is here (bitmap)
}
override fun onPrepareLoad(placeHolderDrawable: Drawable?) {}
override fun onBitmapFailed(e: Exception?, errorDrawable: Drawable?) {}
})
對于Glide
Check 如何使用滑動將圖像下載到位圖中？
對于Universal-Image-Loader
Java代碼
imageLoader.loadImage(imageUrl, new SimpleImageLoadingListener()
{
@Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage)
{
// loaded bitmap is here (loadedImage)
}
});
喵喔喔
TA貢獻1735條經驗 獲得超5個贊
我喜歡這些：
從InputStream創建Bitmap并返回它：
public static Bitmap downloadImage(String url) {
Bitmap bitmap = null;
InputStream stream = null;
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inSampleSize = 1;
try {
stream = getHttpConnection(url);
bitmap = BitmapFactory.decodeStream(stream, null, bmOptions);
stream.close();
}
catch (IOException e1) {
e1.printStackTrace();
System.out.println("downloadImage"+ e1.toString());
}
return bitmap;
}
// Makes HttpURLConnection and returns InputStream
public static InputStream getHttpConnection(String urlString) throws IOException {
InputStream stream = null;
URL url = new URL(urlString);
URLConnection connection = url.openConnection();
try {
HttpURLConnection httpConnection = (HttpURLConnection) connection;
httpConnection.setRequestMethod("GET");
httpConnection.connect();
if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
stream = httpConnection.getInputStream();
}
}
catch (Exception ex) {
ex.printStackTrace();
System.out.println("downloadImage" + ex.toString());
}
return stream;
}
請記?。?/p>
Android包括兩個HTTP客戶端：HttpURLConnection和Apache HTTP Client。 對于姜餅和后來，HttpURLConnection是最好的選擇。
從Android 3.x Honeycomb或更高版本，您無法在UI線程上執行網絡IO并執行此操作會拋出android.os.NetworkOnMainThreadException。您必須使用Asynctask，如下所示
/** AsyncTAsk for Image Bitmap */
private class AsyncGettingBitmapFromUrl extends AsyncTask<String, Void, Bitmap> {
@Override
protected Bitmap doInBackground(String... params) {
System.out.println("doInBackground");
Bitmap bitmap = null;
bitmap = AppMethods.downloadImage(params[0]);
return bitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
System.out.println("bitmap" + bitmap);
}
}
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