Android:没有 Activity 的类中的警报对话框

Question

我有这门课:

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

ImageFromWeb ifw;
private String url;
private final WeakReference<ImageView> imageViewReference;

public DownloadImageTask(ImageView imageView) {
    imageViewReference = new WeakReference<ImageView>(imageView);
}

@Override
protected Bitmap doInBackground(String... params) {
    url = params[0];
    try {
        return BitmapFactory.decodeStream(new URL(url).openConnection().getInputStream());
    } catch (MalformedURLException e) {
        e.printStackTrace();
        return null;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

@Override
protected void onPostExecute(Bitmap result) {
    if (isCancelled()) {
        result = null;
    }
    if (imageViewReference != null) {
        ImageView imageView = imageViewReference.get();
        if (imageView != null) {
            imageView.setImageBitmap(result);
        }
    }
}

@Override
protected void onPreExecute() {
    if (imageViewReference != null) {
        ImageView imageView = imageViewReference.get();
        if (imageView != null) {
 ---------> imageView.setImageResource(R.drawable.pw);     
        }
    }
}

和主要 Activity :

public class ImageFromWeb extends Activity {

private String path = "http://....";
private ImageView imageView;

public void onCreate(Bundle bundle) {
    super.onCreate(bundle);
    setContentView(R.layout.main);

    ImageView mChart = (ImageView) findViewById(R.id.imview);

    mChart.setTag(path);
    new DownloadImageTask(mChart).execute(path);
}

我想在箭头处(在 DownloadImageTask 类中)放置一个警告对话框!我怎样才能做到这一点？因为这个类不是 Activity 。

谢谢:)

Answer 1

更改构造函数并传递一个Context对象

Context mContext;
public DownloadImageTask(ImageView imageView,Context mContext) {
    imageViewReference = new WeakReference<ImageView>(imageView);
    this.mContext = mContext;
}

现在您可以使用这个Context来创建对话框

您甚至可以将 mContext 转换为您的 Activity 类并在您的 Activity 中调用函数