Android: How to detect double-tap?


Question

I have a problem with implementing double tap. Well I implemented the onGestureListener and I had the gestureDetector, but I'm not sure where is the problem, here is my code:

 public class home extends TabActivity implements OnGestureListener {
    /** Called when the activity is first created. */

 private EditText queryText;
 private ResultsAdapter m_adapter;
 private ProgressDialog pd;
 final Handler h = new Handler();
 private TabHost mTabHost;
 private ArrayList<SearchItem> sResultsArr = new ArrayList<SearchItem>();
 private String queryStr;
 private JSONObject searchResponse;
 private GestureDetector gestureScanner;

 final Runnable mUpdateResults = new Runnable() {
        public void run() {
         updateListUi();
        }
    };

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button search = (Button)findViewById(R.id.search);
        Button testButt = (Button)findViewById(R.id.testbutt);
        queryText = (EditText)findViewById(R.id.query);
        ListView lvr = (ListView)findViewById(R.id.search_results);

      //initialise the arrayAdapter
        this.m_adapter = new ResultsAdapter(home.this, R.layout.listrow, sResultsArr);
        lvr.setAdapter(this.m_adapter);
        lvr.setOnItemClickListener(new OnItemClickListener(){
   @Override
   public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
     long arg3) {
    // TODO Auto-generated method stub
         pd = ProgressDialog.show(home.this, null,"Loading products from server", true, false);

   }

        });
        gestureScanner = new GestureDetector(this,this);
        gestureScanner.setOnDoubleTapListener(new OnDoubleTapListener(){ 
            public boolean onDoubleTap(MotionEvent e) { 
                 //viewA.setText("-" + "onDoubleTap" + "-"); 
         pd = ProgressDialog.show(home.this, null,"Loading products from server", true, false);

                 return false; 
            } 
            public boolean onDoubleTapEvent(MotionEvent e) { 
                // viewA.setText("-" + "onDoubleTapEvent" + "-"); 
                 return false; 
            } 
            public boolean onSingleTapConfirmed(MotionEvent e) { 
                 //viewA.setText("-" + "onSingleTapConfirmed" + "-"); 
                 return false; 
            } 

     });


        //initialise tab contents
        mTabHost = getTabHost();
        mTabHost.addTab(mTabHost.newTabSpec("tab1").setIndicator("Home").setContent(R.id.homepage));
        mTabHost.addTab(mTabHost.newTabSpec("tab2").setIndicator("Search Results").setContent(R.id.tab2));
        mTabHost.setCurrentTab(0);

        //sets the respective listeners
        testButt.setOnClickListener(new View.OnClickListener() {
        public void onClick(View arg0) {

         if(mTabHost.getTabWidget().getVisibility()==View.GONE){
          mTabHost.getTabWidget().setVisibility(View.VISIBLE);
         }
         else{
          mTabHost.getTabWidget().setVisibility(View.GONE);
         }
        }
     });

        search.setOnClickListener(new View.OnClickListener() {
        public void onClick(View arg0) {
         sResultsArr.clear();
         queryStr = "http://rose.mosuma.com/mobile?query=" + queryText.getText().toString();
         pd = ProgressDialog.show(home.this, null,"Loading products from server", true, false);
         goSearch();
      }
     });
    }

 //updates the listUI whenever after receiving the response from the server
 public void updateListUi(){  
    if(sResultsArr.size() > 0){

       }

    try{
     String ptypename;
     int count;
     LinearLayout ptypebar = (LinearLayout)findViewById(R.id.productCat);
     ptypebar.removeAllViews();
     JSONArray ptypes = searchResponse.getJSONArray("ptypes"); 
     for(int index =0;index < ptypes.length();index++){
      JSONObject ptype = ptypes.getJSONObject(index);
      count = ptype.getInt("count");      
      ptypename = ptype.getString("ptypename"); 

      //add into tab 2's UI

      //ImageView icon = new ImageView(this);
      TextView t = new TextView(home.this);
      t.setText(ptypename + " (" + count + ")");
      ptypebar.addView(t);
     }
    }
    catch(JSONException e){

    }
   //if(m_adapter.getItems() != sResultsArr){
    ArrayList<SearchItem> a  = m_adapter.getItems(); 
    a = sResultsArr;
   //}
      m_adapter.notifyDataSetChanged();
     pd.dismiss();
 }

 public void goSearch(){
  mTabHost.setCurrentTab(1);

  //separate thread for making http request and updating the arraylist
  Thread t = new Thread() {
           public void run() {

            searchResponse = sendSearchQuery(queryStr);
            try{
             JSONArray results = searchResponse.getJSONArray("results");

             //this is stupid. i probably have to see how to make a json adapter
             for(int index =0;index < results.length();index++){

              JSONObject product = results.getJSONObject(index);

              //gets the searched products from the json object
              URL imgUrl =  new URL(product.getString("image"));
              String productname = product.getString("productname");
              String ptypename = product.getString("ptypename");
              int pid = product.getInt("pid");
              int positive = product.getInt("pos");
              int negative = product.getInt("neg");
              int neutral = product.getInt("neu");


              SearchItem item  = new SearchItem(imgUrl,productname,ptypename,neutral,positive,negative,pid);
              sResultsArr.add(item);
             }
            }
            catch(JSONException e){

            }
            catch(Exception e){

               }
            //returns back to UI therad
            h.post(mUpdateResults);
           }
       };
       t.start();
 }

 //sends a request with qry as URL
 //and receives back a JSONobject as response
 public JSONObject sendSearchQuery(String qry){
  HttpRequest r = new HttpRequest();
  JSONObject response = r.sendHttpRequest(qry);  
  return response;
 }

 @Override
 public boolean onDown(MotionEvent arg0) {
      return gestureScanner.onTouchEvent(arg0); 
 }

 @Override
 public boolean onFling(MotionEvent arg0, MotionEvent arg1, float arg2,
   float arg3) {
  // TODO Auto-generated method stub
  return false;
 }

 @Override
 public void onLongPress(MotionEvent arg0) {
  // TODO Auto-generated method stub

 }

 @Override
 public boolean onScroll(MotionEvent arg0, MotionEvent arg1, float arg2,
   float arg3) {
  // TODO Auto-generated method stub
  return false;
 }

 @Override
 public void onShowPress(MotionEvent arg0) {
  // TODO Auto-generated method stub

 }

 @Override
 public boolean onSingleTapUp(MotionEvent arg0) {
  // TODO Auto-generated method stub
  return false;
 }

Oh, another question, if my ListView has an onItemClickListener, can android detect between single tap or double tap for it?

1
60
11/18/2016 4:23:24 PM

Accepted Answer

Why aren't you using a Long Press? Or are you using that already for something else? The advantages of a Long Press over a Double Touch:

  • Long Press is a recommeded interaction in the UI Guidelines, Double Touch is not.
  • It's what users expect; a user might not find a Double Touch action as they won't go looking for it
  • It's already handled in the API.
  • Implementing a Double Touch will affect handling of Single Touches, because you'll have to wait to see if every Single Touch turns into a Double Touch before you can process it.
19
8/3/2016 7:07:38 AM

You can use the GestureDetector. See the following code:

public class MyView extends View {

    GestureDetector gestureDetector;

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
                // creating new gesture detector
        gestureDetector = new GestureDetector(context, new GestureListener());
    }

    // skipping measure calculation and drawing

        // delegate the event to the gesture detector
    @Override
    public boolean onTouchEvent(MotionEvent e) {
        return gestureDetector.onTouchEvent(e);
    }


    private class GestureListener extends GestureDetector.SimpleOnGestureListener {

        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }
        // event when double tap occurs
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            float x = e.getX();
            float y = e.getY();

            Log.d("Double Tap", "Tapped at: (" + x + "," + y + ")");

            return true;
        }
    }
}

You can override other methods of the listener to get single taps, flinges and so on.


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