从sdcard将图像文件读取到位图中,为什么会出现NullPointerException?


105

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 );  

我正在为位图获取NullPointerException。这意味着位图为空。但是我有一个图像“ .jpg”文件存储在sdcard中,作为“ flower2.jpg”。有什么问题?

Answers:


265

MediaStore API可能会丢弃alpha通道(即,解码为RGB565)。如果您有文件路径,则直接使用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);

要么

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


3
这是selected_photo什么
自治

嗨!“相册”中保存的图像为3840x2160,但通过此方法上传到服务器的图像为1080x1920
Shajeel Afzal

@ ParagS.Chandakkar可能是ImageView,您可以在其中显示解码后的文件。
PinoyCoder


28

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);

6

我编写了以下代码,将图像从sdcard转换为Base64编码的字符串以作为JSON对象发送,并且效果很好:

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);
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