alan alan - 19 days ago 7
Android Question

Android: How to detect double-tap?

hi guys i'm having problems with implementing the 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

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.
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