android - 如何在 Android 中加载大图像并避免内存不足错误？

Question

我正在开发一个使用大图像(1390 × 870:150kb - 50kb)的应用程序。我在点击触发器/ImageView 时添加图像。

在某个时刻，我遇到了内存不足错误:

java.lang.OutOfMemoryError
E/AndroidRuntime(23369): at android.graphics.BitmapFactory.nativeDecodeStream(Native Method)
E/AndroidRuntime(23369): at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:613)
E/AndroidRuntime(23369): at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:378)

要调整图像的大小，我正在这样做:

Bitmap productIndex = null;
final String imageLoc = IMAGE_LOCATION;
InputStream imageStream;
try {
     imageStream = new FileInputStream(imageLoc);
     productIndex = decodeSampledBitmapFromResource(getResources(), imageLoc, 400, 400);

     productIV.setImageBitmap(productIndex);
     } catch (FileNotFoundException e1) {
          // TODO Auto-generated catch block
          e1.printStackTrace();
     }
}


public static Bitmap decodeSampledBitmapFromResource(Resources res, String resId, int reqWidth, int reqHeight) {

// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(resId, options);

// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(resId, options);
}

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;

if (height > reqHeight || width > reqWidth) {

    final int halfHeight = height / 3;
    final int halfWidth = width / 3;

    // Calculate the largest inSampleSize value that is a power of 2 and keeps both
    // height and width larger than the requested height and width.
    while ((halfHeight / inSampleSize) > reqHeight
            && (halfWidth / inSampleSize) > reqWidth) {
        inSampleSize *= 2;
    }
}

return inSampleSize;
}

我从 Android Docs 中得到了这种调整大小以节省空间的方法: Loading Large Bitmaps Efficiently

根据日志，这是 decodeSampledBitmapFromResource 方法中的罪魁祸首:

return BitmapFactory.decodeFile(resId, options);

----- 编辑 -----这是我将每个项目添加到 FrameLayout 的方法。

for(int ps=0;ps<productSplit.size();ps++){
    //split each product by the equals sign
    List<String> productItem = Arrays.asList(productSplit.get(ps).split("="));

    String tempCarID = productItem.get(0);
    tempCarID = tempCarID.replace(" ", "");
    if(String.valueOf(carID).equals(tempCarID)){

        ImageView productIV = new ImageView(Configurator.this);
        LayoutParams productParams = new LayoutParams(
                LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
        productIV.setId(Integer.parseInt(partIdsList.get(x)));
        productIV.setLayoutParams(productParams);

        final String imageLoc = productItem.get(2);

        InputStream imageStream;
        try {
            imageStream = new FileInputStream(imageLoc);
            productIndex = decodeSampledBitmapFromResource(getResources(), imageLoc, 400, 400);
            productIV.setImageBitmap(productIndex);
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        productLayers.addView(productIV);

    }
}

Answer 1

您可以使用另一个位图配置来大幅减小图像的大小。默认值为 RGB-config ARGB8888，这意味着使用四个 8 位 channel (红色、绿色、蓝色、alhpa)。 Alpha 是位图的透明度。这会占用大量内存 - 图像大小 X 4。因此，如果图像大小为 4 兆像素，则将立即在堆上分配 16 兆字节 - 很快就会耗尽内存。

改为 - 使用 RGB_565，这在一定程度上会降低质量 - 但为了弥补这一点，您可以抖动图像。

所以 - 到您的方法 decodeSampledBitmapFromResource - 添加以下 fragment :

 options.inPreferredConfig = Config.RGB_565;
 options.inDither = true;

在您的代码中:

 public static Bitmap decodeSampledBitmapFromResource(Resources res, String resId, int    reqWidth, int reqHeight) {

 // First decode with inJustDecodeBounds=true to check dimensions
 final BitmapFactory.Options options = new BitmapFactory.Options();
 options.inJustDecodeBounds = true;
 BitmapFactory.decodeFile(resId, options);

 // Calculate inSampleSize
 options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

 // Decode bitmap with inSampleSize set
 options.inJustDecodeBounds = false;
 options.inPreferredConfig = Config.RGB_565;
 options.inDither = true;
 return BitmapFactory.decodeFile(resId, options);
 }

引用资料:

http://developer.android.com/reference/android/graphics/Bitmap.Config.html#ARGB_8888