how to fetch data without button click

Question

how to fetch first image without click fetch image button

click to view image

this code work fine but on click fetch image button but i want fetch image with out click fetch images button i want to remove this button

Public class MainActivity extends AppCompatActivity implements 
View.OnClickListener {

    private String imagesJSON;

    private static final String JSON_ARRAY ="result";

    private static final String IMAGE_URL = "url";

    private JSONArray arrayImages= null;

    private int TRACK = 0;

    private static final String IMAGES_URL = "http://www.simplifiedcoding.16mb.com/ImageUpload/getAllImages.php";

    private Button buttonFetchImages;
    private Button buttonMoveNext;
    private Button buttonMovePrevious;
    private ImageView imageView;


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

        imageView = (ImageView) findViewById(R.id.imageView);
        buttonFetchImages = (Button) findViewById(R.id.buttonFetchImages);
        buttonMoveNext = (Button) findViewById(R.id.buttonNext);
        buttonMovePrevious = (Button) findViewById(R.id.buttonPrev);
        buttonFetchImages.setOnClickListener(this);
        buttonMoveNext.setOnClickListener(this);
        buttonMovePrevious.setOnClickListener(this);
    }


    private void extractJSON(){
        try {
            JSONObject jsonObject = new JSONObject(imagesJSON);
            arrayImages = jsonObject.getJSONArray(JSON_ARRAY);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    private void showImage(){
        try {
            JSONObject jsonObject = arrayImages.getJSONObject(TRACK);
            getImage(jsonObject.getString(IMAGE_URL));
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    private void moveNext(){
        if(TRACK < arrayImages.length()){
            TRACK++;
            showImage();
        }
    }

    private void movePrevious(){
        if(TRACK>0){
            TRACK--;
            showImage();
        }
    }



    private void getAllImages() {
        class GetAllImages extends AsyncTask<String,Void,String>{
            ProgressDialog loading;
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                loading = ProgressDialog.show(MainActivity.this, "Fetching Data...","Please Wait...",true,true);
            }

            @Override
            protected void onPostExecute(String s) {
                super.onPostExecute(s);
                loading.dismiss();
                imagesJSON = s;
                extractJSON();
                showImage();
            }

            @Override
            protected String doInBackground(String... params) {
                String uri = params[0];
                BufferedReader bufferedReader = null;
                try {
                    URL url = new URL(uri);
                    HttpURLConnection con = (HttpURLConnection) url.openConnection();
                    StringBuilder sb = new StringBuilder();

                    bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));

                    String json;
                    while((json = bufferedReader.readLine())!= null){
                        sb.append(json+"\n");
                    }

                    return sb.toString().trim();

                }catch(Exception e){
                    return null;
                }
            }
        }
        GetAllImages gai = new GetAllImages();
        gai.execute(IMAGES_URL);
    }

    private void getImage(String urlToImage){
        class GetImage extends AsyncTask<String,Void,Bitmap>{
            ProgressDialog loading;
            @Override
            protected Bitmap doInBackground(String... params) {
                URL url = null;
                Bitmap image = null;

                String urlToImage = params[0];
                try {
                    url = new URL(urlToImage);
                    image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return image;
            }

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                loading = ProgressDialog.show(MainActivity.this,"Downloading Image...","Please wait...",true,true);
            }

            @Override
            protected void onPostExecute(Bitmap bitmap) {
                super.onPostExecute(bitmap);
                loading.dismiss();
                imageView.setImageBitmap(bitmap);
            }
        }
        GetImage gi = new GetImage();
        gi.execute(urlToImage);
    }

    @Override
    public void onClick(View v) {
        if(v == buttonFetchImages) {
            getAllImages();
        }
        if(v == buttonMoveNext){
            moveNext();
        }
        if(v== buttonMovePrevious){
            movePrevious();
        }
    }
}

Answer 1

You can trigger it in onCreate(),but you must not run it on UI thread,for it might be a time-consuming operation.Read Specifying the Code to Run on a Thread to help, you might add the following block in your onCreate() method:

new Runnable() {
        @Override
        public void run() {
            getAllImages();
        }
    }.run();