我正在研究从web服务器下载图像的功能，在屏幕上显示它，如果用户希望保持图像，将其保存在SD卡的某个文件夹中。有没有一种简单的方法来获取位图并将其保存到我选择的SD卡文件夹中?
我的问题是，我可以下载图像，在屏幕上显示为位图。我能够找到的将图像保存到特定文件夹的唯一方法是使用FileOutputStream，但这需要一个字节数组。我不知道如何转换(如果这是正确的方式)从位图到字节数组，所以我可以使用FileOutputStream写入数据。
我的另一个选择是使用MediaStore:
MediaStore.Images.Media.insertImage(getContentResolver(), bm,
barcodeNumber + ".jpg Card Image", barcodeNumber + ".jpg Card Image");
它可以很好地保存到SD卡，但不允许您自定义文件夹。
当前回答
一些新设备不保存位图，所以我解释了一点。
请确保您在下面添加了权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
并在XML文件夹名为provider_paths.xml下创建一个XML文件
<?xml version="1.0" encoding="utf-8"?>
<paths>
<external-path
name="external_files"
path="." />
</paths>
and in AndroidManifest under <provider android:name="android.support.v4.content.FileProvider" android:authorities="${applicationId}.provider" android:exported="false" android:grantUriPermissions="true"> <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/provider_paths"/> </provider> then simply call saveBitmapFile(passYourBitmapHere) public static void saveBitmapFile(Bitmap bitmap) throws IOException { File mediaFile = getOutputMediaFile(); FileOutputStream fileOutputStream = new FileOutputStream(mediaFile); bitmap.compress(Bitmap.CompressFormat.JPEG, getQualityNumber(bitmap), fileOutputStream); fileOutputStream.flush(); fileOutputStream.close(); } where File getOutputMediaFile() { File mediaStorageDir = new File( Environment.getExternalStorageDirectory(), "easyTouchPro"); if (mediaStorageDir.isDirectory()) { // Create a media file name String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss") .format(Calendar.getInstance().getTime()); String mCurrentPath = mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp + ".jpg"; File mediaFile = new File(mCurrentPath); return mediaFile; } else { /// error handling for PIE devices.. mediaStorageDir.delete(); mediaStorageDir.mkdirs(); galleryAddPic(mediaStorageDir); return (getOutputMediaFile()); } } and other methods public static int getQualityNumber(Bitmap bitmap) { int size = bitmap.getByteCount(); int percentage = 0; if (size > 500000 && size <= 800000) { percentage = 15; } else if (size > 800000 && size <= 1000000) { percentage = 20; } else if (size > 1000000 && size <= 1500000) { percentage = 25; } else if (size > 1500000 && size <= 2500000) { percentage = 27; } else if (size > 2500000 && size <= 3500000) { percentage = 30; } else if (size > 3500000 && size <= 4000000) { percentage = 40; } else if (size > 4000000 && size <= 5000000) { percentage = 50; } else if (size > 5000000) { percentage = 75; } return percentage; } and void galleryAddPic(File f) { Intent mediaScanIntent = new Intent( "android.intent.action.MEDIA_SCANNER_SCAN_FILE"); Uri contentUri = Uri.fromFile(f); mediaScanIntent.setData(contentUri); this.sendBroadcast(mediaScanIntent); }
其他回答
Bitmap bbicon;
bbicon=BitmapFactory.decodeResource(getResources(),R.drawable.bannerd10);
//ByteArrayOutputStream baosicon = new ByteArrayOutputStream();
//bbicon.compress(Bitmap.CompressFormat.PNG,0, baosicon);
//bicon=baosicon.toByteArray();
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
OutputStream outStream = null;
File file = new File(extStorageDirectory, "er.PNG");
try {
outStream = new FileOutputStream(file);
bbicon.compress(Bitmap.CompressFormat.PNG, 100, outStream);
outStream.flush();
outStream.close();
} catch(Exception e) {
}
确保在调用bitmap.compress之前创建了目录:
new File(FileName.substring(0,FileName.lastIndexOf("/"))).mkdirs();
为什么不调用Bitmap.compress方法100(这听起来像是无损的)?
在onActivityResult:
String filename = "pippo.png";
File sd = Environment.getExternalStorageDirectory();
File dest = new File(sd, filename);
Bitmap bitmap = (Bitmap)data.getExtras().get("data");
try {
FileOutputStream out = new FileOutputStream(dest);
bitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
}
try (FileOutputStream out = new FileOutputStream(filename)) {
bmp.compress(Bitmap.CompressFormat.PNG, 100, out); // bmp is your Bitmap instance
// PNG is a lossless format, the compression factor (100) is ignored
} catch (IOException e) {
e.printStackTrace();
}
