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我想检查为什么在单击图像按钮时会发生此 looper.prepare() 异常，并且当我按下下载图像的按钮时会发生运行时异常，并且我是 android 中学习线程的新手。请帮助删除此异常

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {
EditText editText ; 
ListView listView;
String [] listOfImages ;
private ProgressBar progressBar;
private LinearLayout loadingSection = null ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = findViewById(R.id.urLList);
        editText = findViewById(R.id.downloadURL);
        progressBar = findViewById(R.id.downloadProgress);
        listOfImages = getResources().getStringArray(R.array.imageUrLs);
        listView.setOnItemClickListener(this);


    }

    public void downloadImage(View view){
//        File file = getExternalFilesDir(Environment.DIRECTORY_DCIM);
//        L.s(this,file.getAbsolutePath());
//        String url = listOfImages[0];
//        Uri uri = Uri.parse(url);
//        L.s(this,uri.getLastPathSegment());

String url = editText.getText().toString();
            Thread myThread = new Thread(new DownloadImagesThread(url));
            myThread.start();

    }

    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
        editText.setText(listOfImages[i]);

    }

    public boolean downloadImageUsingThread(String url) {
        /* 1 create URL object that represent a URL
           2 Open conncetion using the URL object
           3 read data using a input stream into a byte Array
           4 open a file output stream to save data on Sd card
           5 write data to the file output stream
           6 close the connection
         */
        boolean successful = false;
        URL downloadURL = null;
        InputStream inputStream = null;
        HttpURLConnection connection = null;
        FileOutputStream fileOutputStream = null;
        File file = null;
        try {
            downloadURL = new URL(url);
            connection =  (HttpURLConnection) downloadURL.openConnection();
            inputStream = connection.getInputStream();
            file = new File(getExternalFilesDir(Environment.DIRECTORY_DCIM).getAbsolutePath()+"/"+Uri.parse(url).getLastPathSegment(),Environment.DIRECTORY_DCIM);
            fileOutputStream  = new FileOutputStream(file);
          L.s(this,""+file.getAbsolutePath());


            int read = -1 ;
            byte [] buffer = new byte[1024];
            while ((read =inputStream.read(buffer)) != -1){
                fileOutputStream.write(buffer , 0, read);
            }
            successful = true ;


        } catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            if(connection != null){
                connection.disconnect();
            }
            if (inputStream != null){
                try {
                    inputStream.close();
                } catch (IOException e) {

                }
            }
            if (fileOutputStream != null){
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }


        return successful;
    }




    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        //inflate the menu: this add items in prgress bar if it is present
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

//    private class DownloadImagesThread implements Runnable{
//
//        @Override
//        public void run() {
//            downloadImageUsingThread(listOfImages[0]);
//        }
//    }

此类实现线程并在用户按下按钮时用于下载 url 然后触发线程

    private class DownloadImagesThread implements Runnable {
private String url ;

        DownloadImagesThread (String url){
            this.url = url;
        }


        @Override
        public void run() {
            downloadImageUsingThread(url);
        }
    }
}
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