Android：有没有办法确定在edittext软键盘上按键/按下键的时间？

Question

I have an autocomplete edittext field that sends queries to a server everytime the text changes, however if the user types a lot of text and then holds down "delete" I don't want to send a query for every single character deleted. One way of getting around this would be to cache all the queries as the characters were entered and then play back the cache on deletion - but that seems to me to be unnecessarily complicated. An easier way is to detect keydown/keyup and then only send a query if the text has changed but the user also isn't touching the keyboard. Which leads me to the difficulty of how to catch keyup from a softkeyboard.

I've already tried ontouchlistener (doesn't fire) and onkeypressedlistener (also doesnt fire) and even overriding onKeyPreIme inside the edittext (also doesn't fire). Is there a way of doing this?

Answer 1

The way I fixed this problem is to add a delay to the query so it won't execute every time. My code looked something like this:

long lastPress = 0l;
@Override
public void onTextChanged(CharSequence s,
         int start, int before, int count){
    if(System.currentTimeMillis() - lastpress > 500){
        lastPress= System.currentTimeMillis();
        // insert query here
    }
}

Hope this helps.

Answer 2

You can't detect it directly, but you could find an indirect way by overriding the onMeasure in your Activity and detecting when it shrinks and expand over a certain threshold, as long as you define in your Manifest android:windowSoftInputMode to be adjustResize .

In my experience, though, the method is not extremely reliable. You should also consider that the user may leave your activity without closing the keyboard.

It depends on what kind of action you need to take upon deletion, but I was in a similar case where I needed to save the edited text to a shared preference. I found that the best solution is to save it at every character deletion: it's the only safe and consistent method I've found and the performance hit is not noticeable.

Answer 3

Better use TextWatcher

1)Create one TextWatcher listener object :

 private static long time = 0;
 private final  long TIME_DELAY = 700;

 private final TextWatcher myTextWatcher = new TextWatcher() {
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        public void afterTextChanged(Editable s) {
          if(System.currentTimeMillis() - time > TIME_DELAY ){
            time= System.currentTimeMillis();
           // your codes 
           } 

        }
    };

2)Register this listener to your edittext

myEditText.addTextChangedListener(myTextWatcher);

Answer 4

If you only want to identify the delete key pressed in the softkeyboard then try this..

final EditText edit1 = (EditText) findViewById(R.id.editText1); 
edit1.setOnKeyListener(new View.OnKeyListener() { 
    @Override 
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        // You can identify which key pressed buy checking keyCode value 
        // with KeyEvent.KEYCODE_ 
        if (keyCode == KeyEvent.KEYCODE_DEL) {
            // this is for backspace 
            Log.e("IME_TEST", "DEL KEY");
        } 
        return false; 
    } 
}); 

Answer 5

My final solution was to combine Andrea's answer with Jelle's. I record the last time a key was pressed in a textwatcher and only test against it 500 ms after that - in order to know for sure that it was the last key pressed:

private static long lastCharacterPress = 0l;
private Editable stringToSearchFor;
private Handler delayedCharacterCheck;

    edittext.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {

            lastCharacterPress = System.currentTimeMillis();
            stringToSearchFor = s;

            if (s.length() > 2) {

                delayedCharacterCheck.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        checkIfTimeHasPassed();
                    }
                }, 500);

            } else ...

        }
    });

then I put in this method:

private void checkIfTimeHasPassed() {
        if (!TextUtils.isEmpty(stringToSearchFor) && edittext.getText().length() > 2 && System.currentTimeMillis() - lastCharacterPress > 499) {
                // perform the actual query
        }
    }