从 sdcard 将图像文件读入位图时，为什么会出现 NullPointerException？

发布于 2024-12-24 16:52:49 字数 458 浏览 2 评论 0原文

如何从 SD 卡将图像文件读入位图？

 _path = Environment.getExternalStorageDirectory().getAbsolutePath();  

System.out.println("pathhhhhhhhhhhhhhhhhhhh1111111112222222 " + _path);  
_path= _path + "/" + "flower2.jpg";  
System.out.println("pathhhhhhhhhhhhhhhhhhhh111111111 " + _path);  
Bitmap bitmap = BitmapFactory.decodeFile(_path, options );

我收到位图的 NullPointerException 异常。这意味着位图为空。但我有一个图像“.jpg”文件作为“flower2.jpg”存储在SD卡中。有什么问题吗？

原文

How can I read an image file into bitmap from sdcard?

 _path = Environment.getExternalStorageDirectory().getAbsolutePath();  

System.out.println("pathhhhhhhhhhhhhhhhhhhh1111111112222222 " + _path);  
_path= _path + "/" + "flower2.jpg";  
System.out.println("pathhhhhhhhhhhhhhhhhhhh111111111 " + _path);  
Bitmap bitmap = BitmapFactory.decodeFile(_path, options );

I am getting a NullPointerException for bitmap. It means that the bitmap is null. But I have an image ".jpg" file stored in sdcard as "flower2.jpg". What's the problem?

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烟柳画桥 2024-12-31 16:52:49

MediaStore API 可能会丢弃 Alpha 通道（即解码为 RGB565）。如果你有文件路径，只需直接使用 BitmapFactory，但告诉它使用保留 alpha 的格式：

BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
Bitmap bitmap = BitmapFactory.decodeFile(photoPath, options);
selected_photo.setImageBitmap(bitmap);

或

http://mihaifonoage.blogspot.com/2009/09/displaying-images-from-sd-card-in.html

The MediaStore API is probably throwing away the alpha channel (i.e. decoding to RGB565). If you have a file path, just use BitmapFactory directly, but tell it to use a format that preserves alpha:

BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
Bitmap bitmap = BitmapFactory.decodeFile(photoPath, options);
selected_photo.setImageBitmap(bitmap);

http://mihaifonoage.blogspot.com/2009/09/displaying-images-from-sd-card-in.html

回复收藏 0 原文

妄司 2024-12-31 16:52:49

有用：

Bitmap bitmap = BitmapFactory.decodeFile(filePath);

It works:

Bitmap bitmap = BitmapFactory.decodeFile(filePath);

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慢慢从新开始 2024-12-31 16:52:49

试试这个代码：

Bitmap bitmap = null;
File f = new File(_path);
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
try {
    bitmap = BitmapFactory.decodeStream(new FileInputStream(f), null, options);
} catch (FileNotFoundException e) {
    e.printStackTrace();
}         
image.setImageBitmap(bitmap);

Try this code:

Bitmap bitmap = null;
File f = new File(_path);
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
try {
    bitmap = BitmapFactory.decodeStream(new FileInputStream(f), null, options);
} catch (FileNotFoundException e) {
    e.printStackTrace();
}         
image.setImageBitmap(bitmap);

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笔落惊风雨 2024-12-31 16:52:49

我编写了以下代码，将图像从 sdcard 转换为 Base64 编码字符串，以作为 JSON 对象发送。它效果很好：

String filepath = "/sdcard/temp.png";
File imagefile = new File(filepath);
FileInputStream fis = null;
try {
    fis = new FileInputStream(imagefile);
    } catch (FileNotFoundException e) {
    e.printStackTrace();
}

Bitmap bm = BitmapFactory.decodeStream(fis);
ByteArrayOutputStream baos = new ByteArrayOutputStream();  
bm.compress(Bitmap.CompressFormat.JPEG, 100 , baos);    
byte[] b = baos.toByteArray(); 
encImage = Base64.encodeToString(b, Base64.DEFAULT);

I wrote the following code to convert an image from sdcard to a Base64 encoded string to send as a JSON object.And it works great:

String filepath = "/sdcard/temp.png";
File imagefile = new File(filepath);
FileInputStream fis = null;
try {
    fis = new FileInputStream(imagefile);
    } catch (FileNotFoundException e) {
    e.printStackTrace();
}

Bitmap bm = BitmapFactory.decodeStream(fis);
ByteArrayOutputStream baos = new ByteArrayOutputStream();  
bm.compress(Bitmap.CompressFormat.JPEG, 100 , baos);    
byte[] b = baos.toByteArray(); 
encImage = Base64.encodeToString(b, Base64.DEFAULT);

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