Question

我的代码中出现NullPointerException错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference

我有一个位图，它是从Web服务接收的字节中解码得到的。我不明白这个错误。您能帮我纠正代码吗？

我是Android编程的新手，我渴望学习！

这是我的代码：

public class CatListAdapter extends ArrayAdapter {
    ArrayList<String> alNames;
    ArrayList<String> alImages;
    ArrayList<String> alId;
    private Activity context;
    float cornerRadius = 50.0f;
    ImageView imageFlag;

    public CatListAdapter(Activity context, ArrayList<String> alNames, ArrayList<String> alImages,
            ArrayList<String> alId) {
        super(context, R.layout.category_list, alNames);
        this.context = context;
        this.alNames = alNames;
        this.alImages = alImages;
        this.alId = alId;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        LayoutInflater inflater = context.getLayoutInflater();
        if (convertView == null)
            row = inflater.inflate(R.layout.category_list, null, true);
        TextView textViewCountry = (TextView) row.findViewById(R.id.txtcatname);

        imageFlag = (ImageView) row.findViewById(R.id.catimage);

        textViewCountry.setText(alNames.get(position));
        if (String.valueOf(alImages.get(position)) != "") {
            byte[] decode = Base64.decode(alImages.get(position), Base64.DEFAULT);
            Bitmap bitmap = BitmapFactory.decodeByteArray(decode, 0, decode.length);
            bitmapResize(bitmap);
        }
        return row;
    }

    public void bitmapResize(Bitmap imageBitmap) {

        float widthbmp = imageBitmap.getWidth();
        float lengthbmp = imageBitmap.getHeight();
        // Get Screen width
        DisplayMetrics displaymetrics = new DisplayMetrics();
        context.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
        float hight = displaymetrics.heightPixels / 3;
        float width = displaymetrics.widthPixels / 3;

        int convertHighet = (int) hight, convertWidth = (int) width;

        // high length
        if (lengthbmp > hight) {
            convertHighet = (int) hight - 20;
            imageBitmap = Bitmap.createScaledBitmap(imageBitmap, convertWidth, convertHighet, true);
        }

        // high width
        if (widthbmp > width) {
            convertWidth = (int) width - 20;
            imageBitmap = Bitmap.createScaledBitmap(imageBitmap, convertWidth, convertHighet, true);
            imageFlag.setImageBitmap(imageBitmap);
        }
    }
}

Answer 1

首先，请检查byte[] decode是否返回非空值。然后，您在下面添加以下代码行： Bitmap bitmap = BitmapFactory.decodeByteArray(decode, 0, decode.length);

BitmapFactory.Options bmOptions = new BitmapFactory.Options(); bmOptions.inJustDecodeBounds = false;

您可以像这样使用bmOptions： Bitmap bitmap = BitmapFactory.decodeByteArray(decode, 0, decode.length,bmOptions);

要了解实现，您可以参考以下链接：https://developer.android.com/reference/android/graphics/BitmapFactory.Options.html#inJustDecodeBounds

编码愉快！

位图调整大小

1 个答案: