The most common issue that you may face while working with bitmap is OutOfMemoryError. This issue occur because the garbage collector (GC) does not free the object associated with the bitmap and clear preference to pixel data fast enough, thus cause the memory allocated for the bitmap to grow until exceeding Virtual Memory limit.
java.lang.OutOfMemoryError: bitmap size exceeds VM budget
In
order to avoid this issue, you need to do recycle() for every bitmap
as soon as it no long need. Notice that recycle () is used to free
the native object associated with this bitmap, and clear the
reference to the pixel data. This will not free the pixel data
synchronously; it simply allows it to be garbage collected if there
are no other references. The bitmap is marked as “dead”, meaning
it will throw an exception if getPixels() or setPixels() is called,
and will draw nothing. This operation cannot be reversed, so it
should only be called if you are sure there are no further uses for
the bitmap. This is an advanced call, and normally need not be
called, since the normal GC process will free up this memory when
there are no more references to this bitmap. See the code below:
public class bitmaptest extends Activity {
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
// decode a jpg into bitmap
Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/myimage.jpg");
...
// indicate that the bitmap is no longer need and GC should
// free it asap
bitmap.recycle();
}
}
Bimap
is a little tricky, miss-use it may causes an exception. Generally
using bitmap is recommended only if you need to get detail data of
the image such as image
width,
height, and pixel data. Otherwise, bitmap should not be used in order
to avoid OutOfMemoryError. For an example, if you just want to
dispaly an image such as icon, you could you ImageView class instead
and it also provides various display options such as scaling
and
tinting. The following code below shows how to build an
ImageView
that
uses an image from drawable resources and add it to the layout.public class bitmaptest extends Activity {
private LinearLayout mLinearLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Create a LinearLayout in which to add the ImageView
mLinearLayout = new LinearLayout(this);
// Instantiate an ImageView and define its properties
ImageView imageView = new ImageView(this);
imageView.setImageResource(R.drawable.my_image);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setPadding(8, 8, 8, 8);
imageView.setLayoutParams(new GridView.LayoutParams(200, 200));
// Add the ImageView to the layout and set the layout as
// the content view
mLinearLayout.addView(imageView);
setContentView(mLinearLayout);
}
}
