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?

Answer 1

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.

Answer 2

As a lightweight alternative to GestureDetector you can use this class

public abstract class DoubleClickListener implements OnClickListener {      private static final long DOUBLE_CLICK_TIME_DELTA = 300;//milliseconds      long lastClickTime = 0;      @Override     public void onClick(View v) {         long clickTime = System.currentTimeMillis();         if (clickTime - lastClickTime < DOUBLE_CLICK_TIME_DELTA){             onDoubleClick(v);         } else {             onSingleClick(v);         }         lastClickTime = clickTime;     }      public abstract void onSingleClick(View v);     public abstract void onDoubleClick(View v); } 

Example:

    view.setOnClickListener(new DoubleClickListener() {          @Override         public void onSingleClick(View v) {          }          @Override         public void onDoubleClick(View v) {          }     });