空指针异常时，从URL获取图像摆在ImageView的 [英] Null pointer exception when getting image from url to put in imageview

问题描述

我是通过一个网址让我的形象，并试图向设置为我的ImageView。但我发现了一个空指针异常。它甚至没有进入我asynchtask。

有什么我做错了还是没有看到？

 公共类DetailsActivity延伸活动{
    ImageView的缩略图=（ImageView的）findViewById（R.id.btnThumbnail）;
    @覆盖
    保护无效的onCreate（捆绑savedInstanceState）{
        super.onCreate（savedInstanceState）;
        的setContentView（R.layout.detail）;        最终捆绑额外= getIntent（）getExtras（）。
        字符串IMG = extras.getString（缩略图）;
        新DownloadImageTask（（ImageView的）findViewById（R.id.btnThumbnail））
                .execute（http://mysite.com/images/
                        + IMG）;
        }    类DownloadImageTask扩展的AsyncTask＆LT;弦乐，太虚，位图＆GT; {        公共DownloadImageTask（ImageView的bmImage）{
            缩略图= bmImage;
        }        保护位图doInBackground（字符串的URL ...）{
            字符串urldisplay =网址[0];
            Log.e（URL，urldisplay）;
            位图mIcon11 = NULL;
            尝试{
                在的InputStream =新的java.net.URL（urldisplay）.openStream（）;
                mIcon11 = BitmapFactory.de codeStream（中）;
            }赶上（例外五）{
                Log.e（错误，e.getMessage（））;
                e.printStackTrace（）;
            }
            返回mIcon11;
        }        保护无效onPostExecute（位图结果）{
            thumbnail.setImageBitmap（结果）;
        }
    }}
 

解决方案

  ImageView的缩略图=（ImageView的）findViewById（R.id.btnThumbnail）;
 

您需要充气的布局后能得到你的形象，否则 findViewById 将返回空：

  ImageView的缩略图;@覆盖
保护无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.detail）;
    缩略图=（ImageView的）findViewById（R.id.btnThumbnail）
 

I'm getting my image through an URL and trying to set that to my imageView. But I'm getting a Null Pointer Exception. It is not even entering my asynchtask.

Is there something I'm doing wrong or not seeing?

public class DetailsActivity extends Activity {
    ImageView thumbnail = (ImageView) findViewById(R.id.btnThumbnail);


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.detail);

        final Bundle extras = getIntent().getExtras();


        String img = extras.getString("Thumbnail");
        new DownloadImageTask((ImageView) findViewById(R.id.btnThumbnail))
                .execute("http://mysite.com/images/"
                        + img);


        }

    class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {

        public DownloadImageTask(ImageView bmImage) {
            thumbnail = bmImage;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Log.e("URL",urldisplay);
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            thumbnail.setImageBitmap(result);
        }
    }

}

解决方案

ImageView thumbnail = (ImageView) findViewById(R.id.btnThumbnail);

You need to get your image after inflating the layout, otherwise findViewById will returns null :

ImageView thumbnail; 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.detail);
    thumbnail = (ImageView) findViewById(R.id.btnThumbnail)

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