Question

我的AsyncTask中有一个Dialog来显示一些图像的加载。在DIalog中，有一个TextView需要为每个加载的图像更新，但它总是返回NullPointerException。

有人可以帮帮我吗？

这是AsyncTask类的代码：

private class addCartRealms extends AsyncTask<Void, Integer, Void> {

        AlertDialog.Builder mBuilder = new AlertDialog.Builder(mainMenu.this);
        AlertDialog dialog;
        View mView = getLayoutInflater().inflate(R.layout.download_loading_dialog, null);
        TextView numberP = findViewById(R.id.loading_number);
        ProgressBar downloadProgress = findViewById(R.id.download_progress_bar);

        @Override
        protected Void doInBackground(Void... params) {

            final OkHttpClient client = new OkHttpClient();
            Realm myRealm = Realm.getDefaultInstance();

            for (int i = 0; i < downloadedCardList.size(); i++) {

                publishProgress(i);

                myRealm.beginTransaction();
                //ADDING CARDS TO REALM
                Card card = myRealm.createObject(Card.class);
                card.setDankness(downloadedCardList.get(i).getDankness());
                card.setExpansion(downloadedCardList.get(i).getExpansion());
                card.setId(downloadedCardList.get(i).getId());
                card.setImgpath(downloadedCardList.get(i).getImgpath());
                card.setLitness(downloadedCardList.get(i).getLitness());
                card.setName(downloadedCardList.get(i).getName());
                card.setRarity(downloadedCardList.get(i).getRarity());
                card.setValue(downloadedCardList.get(i).getValue());

                Request request = new Request.Builder()
                        .url(downloadedCardList.get(i).getImgpath())
                        .build();

                Response response = null;
                Bitmap image = null;
                try {
                    response = client.newCall(request).execute();

                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (response.isSuccessful()) {

                    image = BitmapFactory.decodeStream(response.body().byteStream());
                    ByteArrayOutputStream stream = new ByteArrayOutputStream();
                    image.compress(Bitmap.CompressFormat.PNG, 100, stream);
                    byte[] byteArray = stream.toByteArray();
                    card.setCardImage(byteArray);

                }

                myRealm.commitTransaction();

                //cardImgUrl.add(new cardImagesAndLink(downloadedCardList.get(i).getImgpath(), downloadedCardList.get(i).getId()));

            }


            return null;
        }
        @Override
        protected void onPostExecute(Void result) {

            dialog.dismiss();
            Toast.makeText(mainMenu.this, "Download completato, scaricate " + downloadedCardList.size() + " carte.", Toast.LENGTH_LONG).show();

        }

        @Override
        protected void onPreExecute() {

            mBuilder.setView(mView);
            dialog = mBuilder.create();
            dialog.show();

        }

        @Override
        protected void onProgressUpdate(Integer... values) {

            numberP.setText(values[0] + " / "  + downloadedCardList.size()); // HERE IS THE ERROR

        }



    }

错误就是这个：

尝试在空对象引用上调用虚方法'void android.widget.TextView.setText（java.lang.CharSequence）'

Answer 1

而不是

header .highlight, header .current a {
  color: #e8491d;
  font-weight: bold;
}

header a:link {
  text-decoration: none;
}

header a:visited {
  text-decoration: none;
}

header a:active {
  text-decoration: none;
}

header a:hover {
  color: #fff;
  font-weight: bold;
  text-decoration: none;
}

您应该使用对话视图

TextView numberP = findViewById(R.id.loading_number);

如果ProgressBar视图包含在对话框布局

中，可能也会这样做

Answer 2

使用对话框func saveMixToDisk() { do { AudioKit.output = offlineRender for track in tracks { let trackSampler = AKMIDISampler() try trackSampler.loadWav(track.instrument.fileName) trackSampler.connect(to: mixer) let sequencer = AKSequencer(filename: track.midi.fileName) sequencer.setTempo(Double(tempo)) sequencer.setRate(rate) sequencer.setGlobalMIDIOutput(trackSampler.midiIn) sequencer.enableLooping() offlineSequencers.append(sequencer) trackSampler >>> offlineRender } AudioKit.start() let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first! let destinationAudioFile = docs.appendingPathComponent("\(UUID().uuidString).m4a") offlineRender.internalRenderEnabled = false for sequencer in offlineSequencers { sequencer.play() } try offlineRender.renderToURL(destinationAudioFile, seconds: offlineSequencers.first!.length.seconds) for sequencer in offlineSequencers { sequencer.stop() } offlineRender.internalRenderEnabled = true } catch let error { print(error) } }，如下所示：

findViewById

AsyncTask中的Dialog TextView始终为null

2 个答案: