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このクラスを現在使用しているURLところから画像を取得しようとしています。インターネットのwrite_SDカードなどに接続する権限を追加しましたが、この関数を使用して画像を追加しようとするとエラーが返されるという問題があります：`ImageViewAndroidManifestjava.lang.NullPointerExceptionImageView

public void download(String url, ImageView imageView) {
    try
    {    
        if (cancelPotentialDownload(url, imageView)) 
        {
             //TODO:Caching code right here
             String filename = String.valueOf(url.hashCode());
             File f = new File(getCacheDirectory(hm), filename);

              // Is the bitmap in our cache?
              Bitmap bitmap = BitmapFactory.decodeFile(f.getPath());

              //No? download it
              if(bitmap == null){
                  BitmapDownloaderTask task = new BitmapDownloaderTask(imageView);
                  DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task);
                  imageView.setImageDrawable(downloadedDrawable);
                  task.execute(url);
              }else{
                  //Yes? set the image
                  imageView.setImageBitmap(bitmap);
              }
         }
    }catch (Exception e) {
        // TODO: handle exception
        Log.e("",e.toString());
    }
}`

問題は、何が間違っている可能性があり、どうすればこれを修正できるかということです。私を正しい方向に向けていただければ幸いです。

Logcat：

`06-06 09:38:19.686: E/AndroidRuntime(18832): java.lang.NullPointerException
06-06 09:38:19.686: E/AndroidRuntime(18832):    at com.jandans.geos.ImageDownloader.download(ImageDownloader.java:51)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at com.jandans.geos.vaikpied$1.onItemClick(vaikpied.java:98)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.widget.AdapterView.performItemClick(AdapterView.java:284)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.widget.ListView.performItemClick(ListView.java:3513)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:1849)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.os.Handler.handleCallback(Handler.java:587)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.os.Looper.loop(Looper.java:130)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at android.app.ActivityThread.main(ActivityThread.java:3835)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at java.lang.reflect.Method.invokeNative(Native Method)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at java.lang.reflect.Method.invoke(Method.java:507)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
06-06 09:38:19.686: E/AndroidRuntime(18832):    at dalvik.system.NativeStart.main(Native Method)

`

4

2 に答える 2

1

以下のスニペットが役立ちます。

DownloadHelper.java

public interface DownloadHelper
{
    public void OnSucess(Bitmap bitmap);
    public void OnFailure(String response);
}

MainActivity.java

public class GalleryExample extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);

        DownloadHelper downloadHelper = new DownloadHelper()
        {
            @Override
            public void OnSucess(Bitmap bitmap)
            {
                ImageView imageView=(ImageView)findViewById(R.id.imageView);
                imageView.setImageBitmap(bitmap);
            }

            @Override
            public void OnFailure(String response)
            {
                Toast.makeText(context, response, Toast.LENGTH_LONG).show();
            }
        };
        new MyTask(this,downloadHelper).execute("image url");
    }

MyTask.java

public class DownloadTask extends AsyncTask<String, Integer, Object>
{
    private Context context;
    private DownloadHelper downloadHelper;
    private ProgressDialog dialog;


    public DownloadTask(Context context,DownloadHelper downloadHelper)
    {
        this.context = context;

    }

    @Override
    protected void onPreExecute()
    {
        dialog = new ProgressDialog(context);
        dialog.setTitle("Please Wait");
        dialog.setMessage("Fetching Data!!");
        dialog.setCancelable(false);
        dialog.show();
        super.onPreExecute();
    }

    @Override
    protected Object doInBackground(String... params)
    {
        URL aURL = new URL(myRemoteImages[position]);
        URLConnection conn = aURL.openConnection();
        conn.connect();
        InputStream is = conn.getInputStream();

        BufferedInputStream bis = new BufferedInputStream(is);
        /* Decode url-data to a bitmap. */
        Bitmap bm = BitmapFactory.decodeStream(bis);
        bis.close();
        is.close();
        return bm;
    }

    @Override
    protected void onPostExecute(Object result)
    {
        dialog.dismiss();
        if (result != null)
        {
            downloadHelper.OnSucess((Bitmap)result);
        } 
        else
        {
            downloadHelper.OnFailure("Error in Downloading Data!!");
        }
        super.onPostExecute(result);
    }
}
于 2012-06-06T06:48:17.807 に答える
1

以下を試してください-

public class ImgLoadFrmWebActivity extends Activity {

    ImageView imv1;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Drawable image = ImageOperations(getApplicationContext(),"http://hvz.eu5.org/upload/1.jpg","image");
        ImageView imgView = (ImageView)findViewById(R.id.imageView1);
        imgView = (ImageView)findViewById(R.id.imageView1);
        imgView.setImageDrawable(image);
    }
    private Drawable ImageOperations(Context ctx, String url, String saveFilename) {
        try {
            InputStream is = (InputStream) this.fetch(url);
            Drawable d = Drawable.createFromStream(is, "src");
            return d;
        } catch (MalformedURLException e) {
            e.printStackTrace();
            return null;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public Object fetch(String address) throws MalformedURLException,IOException {
        URL url = new URL(address);
        Object content = url.getContent();
        return content;
    }
}

マニフェストファイルに権限が追加されていることを確認してください-

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

必要に応じてこのレイアウトをカスタマイズするだけです。これがお役に立てば幸いです。

于 2012-06-06T06:49:13.510 に答える