Android - 在加载到 ImageView 之前调整图像大小以避免 OOM 问题

Question

从图库/照片中选择后，如何在 imageview 上减小图像大小？否则选择的大图像会导致 OOM 问题。

选择意图

SelectImageGallery1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent, "Select Image1 From Gallery"), 1);
    }
}

设置为 ImageView：

{
    Uri uri = I.getData();
    try {
        bitmap1 = MediaStore.Images.Media.getBitmap(getContentResolver(), uri);
        imageView1.setImageBitmap(bitmap1);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 1

查看文档的Loading Large Bitmaps Efficiently 部分，特别是Load a Scaled Down Version into Memory (https://developer.android.com/topic/performance/graphics/load-bitmap#load-bitmap)

通过设置inSampleSize，您可以在加载之前控制Bitmap 的大小。

来自文档：

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

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

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

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeResource(res, 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 / 2;
        final int halfWidth = width / 2;

        // 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;
}

文档使用资源作为示例，但您应该能够通过抓取InputStream 来使用ContentResolver 并改用BitmapFactory.decodeStream(...)

ContentResolver cr = getApplicationContext().getContentResolver();
InputStream is = cr.openInputStream(uri);

Answer 2

我终于使用 glide 解决了它，如下所示，以供将来可能需要它的人使用。 选择意图

SelectImageGallery1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent, "Select Image1 From Gallery"), 1);
    }
}

使用 Glide 将图像设置为 Imageview

    @Override
    protected void onActivityResult(int RC, int RQC, Intent I) {
        super.onActivityResult(RC, RQC, I);
        if (RC == 1 && RQC == RESULT_OK && I != null && I.getData() != null) {
            Uri uri = I.getData();
            RequestOptions options = new RequestOptions()
                    .format(DecodeFormat.PREFER_RGB_565)
                    .placeholder(R.drawable.ic_launcher_background)
                    .error(R.drawable.ic_launcher_background);

            Glide.with(this)
                    .setDefaultRequestOptions(options)
                    .asBitmap()
                    .load(uri)
                    .centerInside()
                    .into(new CustomTarget<Bitmap>(512, 512) {
                        @Override
                        public void onResourceReady(@NonNull Bitmap bitmap1, @Nullable Transition<? super Bitmap> transition) {
                            imageView1.setImageBitmap(bitmap1);
                            MainActivity.this.bitmap1 = bitmap1;
                        }

                        @Override
                        public void onLoadCleared(@Nullable Drawable placeholder) {
                        }
                    });
        }

Answer 3

为此目的使用毕加索

implementation 'com.squareup.picasso:picasso:2.71828'

并使用此代码加载图像

Picasso.get()
    .load(R.drawable.landing_screen)
    .resize(50, 50)
    .into(imageView1);

欲了解更多信息，请访问链接：

https://square.github.io/picasso/

您也可以使用它来从网络异步加载图像，而无需自己进行任何 HTTP 请求。