Question

我的应用程序中有一个List View，我通过Base Adapter显示数据。他们是我面临的两个问题，并提到几个帖子，但所有建议我遵循相同的程序。

问题

我正在尝试从JSON提供的URL下载图像。一切顺利，但图像永远不会设置为Image View。
我将Text to Speech绑定到Base Adapter类中的按钮的单击事件并将其释放到java类的onDestroy中但仍然在Log中出现错误，因为它说明了this和应用程序崩溃。在log erroe行中，第55行是onDestroy的第一个陈述。

这是我的代码

Java文件

public class DisplayWeather extends Activity {

    String city, date, maximumTemp, minimumTemp, description, weatherImageUrl;
    ListView weatherList;
    List <Bean> bean;
    Bitmap myBitmap, newBitmap;
    CustomBaseAdapter baseAdapter;

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

        bean = new ArrayList<Bean>();
        weatherList = (ListView) findViewById(R.id.lvWeather);

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

        }


        weatherList.setAdapter(new CustomBaseAdapter(this, bean));
    }


    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        if (baseAdapter.tts != null)
        {
            baseAdapter.tts.stop();
            baseAdapter.tts.shutdown();
        }
        super.onDestroy();
    }

基础适配器类

public class CustomBaseAdapter extends BaseAdapter implements OnInitListener {
    Context context;
    List<Bean> bean;
    ImageView weatherImage;
    TextView weatherDate, weatherCity, weatherMinimum, weatherMaximum, weatherDescription;
    Button buttonSpeak;
    String citySpeak, dateSpeak, descriptionSpeak, maximumSpeak, minimumSpeak, weatherURL;
    TextToSpeech tts;
    Bean userBean;
    Bitmap myBitmap;

    public CustomBaseAdapter(Context context, List<Bean> bean) {
        // TODO Auto-generated constructor stub
        this.context = context;
        this.bean = bean;
        tts = new TextToSpeech(context, null);
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return bean.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return bean.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return bean.indexOf(getItem(position));
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);

        if(convertView == null)
        {
            convertView = inflater.inflate(R.layout.custom_base_adapter, null);
            weatherImage = (ImageView) convertView.findViewById(R.id.displayImage);
convertView.findViewById(R.id.displayDate);
            buttonSpeak = (Button) convertView.findViewById(R.id.Speak);


        }

        weatherURL = userBean.getImageUrl();

        new ImageDownload().execute();

        Log.i("Executing Rest Line>>>", "Skippedddddd");
        buttonSpeak.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
            String cityName = weatherCity.getText().toString(); 
            String dateValue = weatherDate.getText().toString();
            String maximumValue = weatherMaximum.getText().toString();
            String minimumValue = weatherMinimum.getText().toString();
            String descriptionValue = weatherDescription.getText().toString();

            citySpeak = "Temprature for city "+cityName+"";
            dateSpeak = " on Date "+dateValue+"";
            maximumSpeak = "will be Maximum upto "+maximumValue+" degree ";
            minimumSpeak = " and Minimum upto"+minimumValue+" degree ";
            descriptionSpeak = "and The atmosphere seems to be "+descriptionValue+"";

            speakTempratureValues();
            }
        });

        return convertView;
    }

    private class ImageDownload extends AsyncTask<String, Void, Bitmap>{

        protected Bitmap doInBackground(String... arg0){

            try{
                Log.e("src",weatherURL);
                URL url = new URL(weatherURL);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setDoInput(true);
                connection.connect();
                InputStream input = connection.getInputStream();
                myBitmap = BitmapFactory.decodeStream(input);       
                Log.e("Bitmap","returned");
                return myBitmap;
            }
            catch(Exception e){
                e.printStackTrace();
                return null;
            }

        }

        protected void onPostExecute(Bitmap result){
             if(result!=null)
             {
                Log.i("OnPost>>>", ""+result);
                weatherImage.setImageBitmap(result);
             }

        }
    }

    protected void speakTempratureValues() {
        // TODO Auto-generated method stub
        tts.setSpeechRate(-4);
        tts.speak(citySpeak, TextToSpeech.QUEUE_FLUSH, null);
        tts.speak(dateSpeak, TextToSpeech.QUEUE_ADD, null);
        tts.speak(maximumSpeak, TextToSpeech.QUEUE_ADD, null);
        tts.speak(minimumSpeak, TextToSpeech.QUEUE_ADD, null);
        tts.speak(descriptionSpeak, TextToSpeech.QUEUE_ADD, null);
        tts.speak("Thank You", TextToSpeech.QUEUE_ADD, null);
    }


    @Override
    public void onInit(int status) {
        // TODO Auto-generated method stub
        if(status==TextToSpeech.SUCCESS){
            int result = tts.setLanguage(Locale.getDefault());

            if (result == TextToSpeech.LANG_MISSING_DATA
                    || result == TextToSpeech.LANG_NOT_SUPPORTED) {
                Log.e("TTS", "This Language is not supported");
            }
            else{

                speakTempratureValues();
            }
        }
        else{
            Log.e("TTS", "Initialization Failed");
        }
    }

}

Answer 1

在您的AsyncTask下载完图像之前，您可能会在getView方法中返回convertView。您是否可以使用线程，并使用线程连接方法，以便您的应用程序等待下载图像？对于AsyncTask，您通常会使用进度对话框，直到任务完成，但我不认为您可以在适配器内执行此操作。

如何替换它：

new ImageDownload().execute();

用这个：

new Thread(new Runnable() {
public void run() {
  try{
            Log.e("src",weatherURL);
            URL url = new URL(weatherURL);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.connect();
            InputStream input = connection.getInputStream();
            myBitmap = BitmapFactory.decodeStream(input);       
            Log.e("Bitmap","returned");
            return myBitmap;
        }
        catch(Exception e){
            e.printStackTrace();
            return null;
        }}
}).join();

然后显然摆脱了ImageDownload类。我只是把它丢给你，没有测试它或任何东西。我认为这应该让你更接近。

Answer 2

路易斯建议的是正确的方法。我相信这会奏效。它不适合你的原因并不确定，但尝试这种方式：

Runnable runnable = new Runnable() {

                @Override
                public void run() {
                    // TODO Auto-generated method stub
                    try{
                        Log.e("src",weatherURL);
                        URL url = new URL(weatherURL);
                        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                        connection.setDoInput(true);
                        connection.connect();
                        InputStream input = connection.getInputStream();
                        myBitmap = BitmapFactory.decodeStream(input);       
                        Log.e("Bitmap","returned"+myBitmap);

                        if(myBitmap!=null)
                     {
                        Log.i("OnPost>>>", ""+myBitmap);
                        weatherImage.setImageBitmap(myBitmap);
                     }
                    }
                    catch(Exception e){
                        e.printStackTrace();

                    }

                }
            };

            Thread t = new Thread(runnable);
            t.start();
            try {
                t.join();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

可能是你缺少start方法，你可能没有调用它。我希望这项工作。

从URL下载图像

2 个答案: