listView.getFirstVisiblePosition()有错误

问题描述 投票:0回答:1

我正在基于我在互联网上找到的一个例子创建一个带有android的多上传屏幕。我做了一些简单的修改,使得每个文件发送给谁,传递给下一个列表。我用了这些简单的线条:

int n = ImageList.size()-1;
if (position<n) {
   startUpload(position + 1);
}

这是链接上的完整代码。

例如:http://www.thaicreate.com/mobile/android-upload-file-show-items-progressbar-listview.html

更多的部分。问题是当它自动进入listview的问题字段并且在屏幕上看不到系统停止并且它消息和错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById (int)' on a null object reference.

我已经搜索了论坛,但我找不到解决方案。

此行中出现错误:

View v = lstView.getChildAt(position - lstView.getFirstVisiblePosition());

完整代码:

public class MainActivity extends Activity  {

    private ListView lstView;
    private Handler handler = new Handler();
    private int counter = 0;
    List <String> ImageList;
    private ProgressBar progress;
    private TextView status;
    private Button btnUpload;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        /*** Get Images from SDCard ***/
        ImageList = getSD();

        // ListView and imageAdapter
        lstView = (ListView) findViewById(R.id.listView1);
        lstView.setAdapter(new ImageAdapter(this));

    }


    private List <String> getSD()
    {
        List <String> it = new ArrayList <String>();
        File f = new File ("/mnt/sdcard/RAIOTOI/photo/");
        File[] files = f.listFiles ();

        for (int i = 0; i <files.length; i++)
        {
            File  file = files[i];
            Log.d("Count",file.getPath());
            it.add (file.getPath());
        }
        return it;
    }

    public class ImageAdapter extends BaseAdapter
    {
        private Context context;

        public ImageAdapter(Context c)
        {
            // TODO Auto-generated method stub
            context = c;
        }

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

        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public View getView(final int position, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub

            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);


            if (convertView == null) {
                convertView = inflater.inflate(R.layout.activity_column, null);
            }

            status = (TextView) convertView.findViewById(R.id.ColStatus);
            btnUpload = (Button) convertView.findViewById(R.id.btnUpload);

            // ColImgName
            TextView txtName = (TextView) convertView.findViewById(R.id.ColImgName);
            String strPath = ImageList.get(position).toString();

            // Get File Name
            String fileName = strPath.substring( strPath.lastIndexOf('/')+1, strPath.length() );
            File file = new File(strPath);
            long length = file.length();
            txtName.setPadding(3, 0, 0, 0);
            txtName.setText(fileName + " ("+length/1024+" KB.)");

            // Image Resource
            ImageView imageView = (ImageView) convertView.findViewById(R.id.ColImgPath);
            imageView.getLayoutParams().height = 110;
            imageView.getLayoutParams().width = 110;
            imageView.setPadding(10, 10, 2, 10);
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            Bitmap bm = BitmapFactory.decodeFile(strPath);
            imageView.setImageBitmap(bm);


            // ColStatus
            final TextView txtStatus = (TextView) convertView.findViewById(R.id.ColStatus);
            txtStatus.setPadding(3, 0, 0, 0);
            txtStatus.setText("...");

            // progressBar
            progress = (ProgressBar) convertView.findViewById(R.id.progressBar);
            progress.setVisibility(View.GONE);
            progress.setPadding(0, 0, 0, 0);

            //btnUpload
            final Button btnUpload = (Button) convertView.findViewById(R.id.btnUpload);
            btnUpload.setTextColor(Color.BLACK);
            btnUpload.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // Upload
                    btnUpload.setEnabled(false);
                    btnUpload.setTextColor(Color.GRAY);
                    startUpload(position);
                }
            });


            return convertView;

        }
    }

    //Upload
    public void startUpload(final int position) {

        Runnable runnable = new Runnable() {

            public void run() {

                handler.post(new Runnable() {
                    public void run() {


                        View v = lstView.getChildAt(position - lstView.getFirstVisiblePosition());

                        // Show ProgressBar
                        ProgressBar progress = (ProgressBar) v.findViewById(R.id.progressBar);
                        progress.setVisibility(View.VISIBLE);

                        // Status
                        status = (TextView) v.findViewById(R.id.ColStatus);
                        status.setText("Enviando...");

                        new UploadFileAsync().execute(String.valueOf(position));

                    }
                });

            }
        };
        new Thread(runnable).start();
    }


    // Async Upload
    public class UploadFileAsync extends AsyncTask<String, Void, Void> {

        String resServer;
        int position;

        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(String... params) {
            // TODO Auto-generated method stub
            position = Integer.parseInt(params[0]);

            int bytesRead, bytesAvailable, bufferSize;
            byte[] buffer;
            int maxBufferSize = 1 * 1024 * 1024;
            int resCode = 0;
            String resMessage = "";

            String lineEnd = "\r\n";
            String twoHyphens = "--";
            String boundary =  "*****";

            // File Path
            String strSDPath = ImageList.get(position).toString();

            // Upload to PHP Script
            String strUrlServer = "http://192.168.1.134:8080/up.php";

            try {
                /** Check file on SD Card ***/
                File file = new File(strSDPath);
                if(!file.exists())
                {
                    resServer = "{\"StatusID\":\"0\",\"Error\":\"Please check path on SD Card\"}";
                    return null;
                }

                FileInputStream fileInputStream = new FileInputStream(new File(strSDPath));

                URL url = new URL(strUrlServer);
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setDoInput(true);
                conn.setDoOutput(true);
                conn.setUseCaches(false);
                conn.setRequestMethod("POST");

                conn.setRequestProperty("Connection", "Keep-Alive");
                conn.setRequestProperty("Content-Type",
                        "multipart/form-data;boundary=" + boundary);

                DataOutputStream outputStream = new DataOutputStream(conn
                        .getOutputStream());
                outputStream.writeBytes(twoHyphens + boundary + lineEnd);
                outputStream
                        .writeBytes("Content-Disposition: form-data; name=\"filUpload\";filename=\""
                                + strSDPath + "\"" + lineEnd);
                outputStream.writeBytes(lineEnd);

                bytesAvailable = fileInputStream.available();
                bufferSize = Math.min(bytesAvailable, maxBufferSize);
                buffer = new byte[bufferSize];

                // Read file
                bytesRead = fileInputStream.read(buffer, 0, bufferSize);

                while (bytesRead > 0) {
                    outputStream.write(buffer, 0, bufferSize);
                    bytesAvailable = fileInputStream.available();
                    bufferSize = Math.min(bytesAvailable, maxBufferSize);
                    bytesRead = fileInputStream.read(buffer, 0, bufferSize);
                }

                outputStream.writeBytes(lineEnd);
                outputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

                // Response Code and  Message
                resCode = conn.getResponseCode();
                if(resCode == HttpURLConnection.HTTP_OK)
                {
                    InputStream is = conn.getInputStream();
                    ByteArrayOutputStream bos = new ByteArrayOutputStream();

                    int read = 0;
                    while ((read = is.read()) != -1) {
                        bos.write(read);
                    }
                    byte[] result = bos.toByteArray();
                    bos.close();

                    resMessage = new String(result);

                }

                Log.d("resCode=",Integer.toString(resCode));
                Log.d("resMessage=",resMessage.toString());

                fileInputStream.close();
                outputStream.flush();
                outputStream.close();

                resServer = resMessage.toString();


            } catch (Exception ex) {
                // Exception handling
                return null;
            }

            return null;
        }

        protected void onPostExecute(Void unused) {
            statusWhenFinish(position,resServer);
        }

    }

    // When UPload Finish
    protected void statusWhenFinish(int position, String resServer) {

        View v = lstView.getChildAt(position - lstView.getFirstVisiblePosition());

        progress = (ProgressBar) v.findViewById(R.id.progressBar);
        // Show ProgressBar
        progress.setVisibility(View.GONE);


        // Status
        status = (TextView) v.findViewById(R.id.ColStatus);

        /** Get result from Server (Return the JSON Code)
         * StatusID = ? [0=Failed,1=Complete]
         * Error    = ? [On case error return custom error message]
         *
         * Eg Upload Failed = {"StatusID":"0","Error":"Cannot Upload file!"}
         * Eg Upload Complete = {"StatusID":"1","Error":""}
         */

        /*** Default Value ***/
        String strStatusID = "0";
        String strError = "Unknow Status!";

        try {

            JSONObject c = new JSONObject(resServer);
            strStatusID = c.getString("StatusID");
            strError = c.getString("Error");
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        // Prepare Status
        if(strStatusID.equals("0"))
        {
            // When update Failed
            status.setText("FALHOU ("+ strError +")");
            status.setTextColor(Color.RED);

            // Enabled Button again
            btnUpload = (Button) v.findViewById(R.id.btnUpload);
            btnUpload.setText("Repetir");
            btnUpload.setTextColor(Color.RED);
            btnUpload.setEnabled(true);
        }
        else
        {
            status.setText("Envio completo.");
            status.setTextColor(Color.GREEN);

            btnUpload.setEnabled(false);
            btnUpload.setTextColor(Color.GRAY);


            int n = ImageList.size()-1;
            Log.i("IDID", " "+position+" "+n);
            if (position<n) {
                startUpload(position + 1);
            }
        }

    }

}
android listview
1个回答
0
投票

你的lstView是null,请确保你先findViewById()它。

© www.soinside.com 2019 - 2024. All rights reserved.