Java 如何检查 ImageView 是否包含 Bitmap？
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原文地址: http://stackoverflow.com/questions/20324048/
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How to check if ImageView contains Bitmap or not?
提问by amita
I am implementing if a ImageViewhas bitmap then it should save the image from imageview to internal memory ,otherwise set another bitmap in internal memory of application.
here is code:_
我正在实现如果一个ImageView位图那么它应该将图像从 imageview 保存到内部存储器，否则在应用程序的内部存储器中设置另一个位图。这是代码：_
croppedImage = cropImageView.getCroppedImage();
croppedImageView = (ImageView) findViewById(R.id.croppedImageView);
croppedImageView.setImageBitmap(croppedImage);@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.btn_save:
counter++;
if(croppedImageView.getDrawable() != null)
{
System.out.println("nullllllllllllll");
try {
Bitmap photo = ((BitmapDrawable)croppedImageView.getDrawable()).getBitmap();
FileOutputStream mFileOutStream1 = openFileOutput("IMG" + counter + ".png", Context.MODE_PRIVATE);
photo.compress(CompressFormat.JPEG, 100, mFileOutStream1);}
catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();}
}else{
System.out.println("notttttnullllllllllllll");
try {
FileOutputStream mFileOutStream1 = openFileOutput("IMG" + counter + ".png", Context.MODE_PRIVATE);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, mFileOutStream1);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Editor editor = def.edit();
editor.putInt("value", counter);
editor.commit();
break;
default:
break;
}
}
采纳答案by Amulya Khare
You can check it as follows:
您可以按如下方式检查：
boolean hasDrawable = (croppedImageView.getDrawable() != null);
if(hasDrawable) {
// imageView has image in it
}
else {
// no image assigned to image view
}
Just check only Bitmap value as below :
只需检查如下位图值：
if(bitmap == null) {
// set the toast for select image
} else {
uploadImageToServer();
}
回答by Alexander Abakumov
The accepted answeris not correctfor at least one case: when you previously set ImageViews Bitmapto nullvia:
至少在一种情况下，接受的答案不正确：当您之前将ImageViews设置Bitmap为nullvia 时：
imageView.setImageBitmap(null);
actually it would NOT set the internal Drawableto null. So, the proposed in the accepted answer check will give you incorrect result.
实际上它不会将内部设置Drawable为null. 因此，接受的答案检查中的建议会给您不正确的结果。
You can easily find out what's going on in the ImageViewsource code:
您可以轻松找出ImageView源代码中发生的事情：
public void setImageBitmap(Bitmap bm) {
// if this is used frequently, may handle bitmaps explicitly
// to reduce the intermediate drawable object
setImageDrawable(new BitmapDrawable(mContext.getResources(), bm));
}
Meaning that instead of setting its internal Drawableto null, it sets it to a newly created BitmapDrawablewith nullBitmap.
这意味着不是将其内部设置Drawable为null，而是将其设置为新创建BitmapDrawable的nullBitmap.
Therefore, the correct method of checking whether an ImageViewhas somewhat meaningful Drawableissomething like:
因此，检查 an 是否ImageView具有某种意义的正确方法Drawable是：
publie static boolean hasNullOrEmptyDrawable(ImageView iv)
{
Drawable drawable = iv.getDrawable();
BitmapDrawable bitmapDrawable = drawable instanceof BitmapDrawable ? (BitmapDrawable)drawable : null;
return bitmapDrawable == null || bitmapDrawable.getBitmap() == null;
}
Moreover, looking at this behavior in the source code, one might suppose that nullDrawbleis something Android SDK developers try to avoid. That's why you should avoid relying on getDrawable() == nullcheck in your code at all.
此外，查看源代码中的这种行为，人们可能会认为这nullDrawble是 Android SDK 开发人员试图避免的事情。这就是为什么您应该完全避免依赖getDrawable() == null检查代码的原因。
