Android - Hold Button to Repeat Action
I'll admit straight off that I'm new to development and trying my hand at Android. I've been trying to search the 'net to find advice on how to implement some "Hold Button to Repeat Action" - I've created a custom numpad from buttons and want a backspace-like behaviour. Having got so far, I called upon a friend who hasn't coded Android before, but done lots of C# / Java and seems to know what he's doing.
The code below works just fine, but I feel it could be done more neatly. I apologise if I've missed bits out, but hopefully this explains my approach. I think the onTouchListener is ok, but the way Threads are handled doesn't feel right.
Is there a better or more simple way to do this?
public class MyApp extends Activity {
private boolean deleteThreadRunning = false;
private boolean cancelDeleteThread = false;
private Handler handler = new Handler();
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
//May have missed some declarations here...
Button_Del.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
{
handleDeleteDown();
return true;
}
case MotionEvent.ACTION_UP:
{
handleDeleteUp();
return true;
}
default:
return false;
}
}
private void handleDeleteDown() {
if (!deleteThreadRunning)
startDeleteThread();
}
private void startDeleteThread() {
Thread r = new Thread() {
@Override
public void run() {
try {
deleteThreadRunning = true;
while (!cancelDeleteThread) {
handler.post(new Runnable() {
@Override
public void run() {
deleteOneChar();
}
});
try {
Thread.sleep(100);
} catch (InterruptedException e) {
throw new RuntimeException(
"Could not wait between char delete.", e);
}
}
}
finally
{
deleteThreadRunning = false;
cancelDeleteThread = false;
}
}
};
// actually start the delete char thread
r.start();
}
});
}
private void handleDeleteUp() {
cancelDeleteThread = true;
}
private void deleteOneChar()
{
String result = getNumberInput().getText().toString();
int Length = result.length();
if (Length > 0)
getNumberInput().setText(result.substring(0, Length-1));
//I've not pasted getNumberInput(), but it gets the string I wish to delete chars from
}
This is more independent implementation, usable with any View, that supports touch event:
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
/**
* A class, that can be used as a TouchListener on any view (e.g. a Button).
* It cyclically runs a clickListener, emulating keyboard-like behaviour. First
* click is fired immediately, next one after the initialInterval, and subsequent
* ones after the normalInterval.
*
* <p>Interval is scheduled after the onClick completes, so it has to run fast.
* If it runs slow, it does not generate skipped onClicks. Can be rewritten to
* achieve this.
*/
public class RepeatListener implements OnTouchListener {
private Handler handler = new Handler();
private int initialInterval;
private final int normalInterval;
private final OnClickListener clickListener;
private View touchedView;
private Runnable handlerRunnable = new Runnable() {
@Override
public void run() {
if(touchedView.isEnabled()) {
handler.postDelayed(this, normalInterval);
clickListener.onClick(touchedView);
} else {
// if the view was disabled by the clickListener, remove the callback
handler.removeCallbacks(handlerRunnable);
touchedView.setPressed(false);
touchedView = null;
}
}
};
/**
* @param initialInterval The interval after first click event
* @param normalInterval The interval after second and subsequent click
* events
* @param clickListener The OnClickListener, that will be called
* periodically
*/
public RepeatListener(int initialInterval, int normalInterval,
OnClickListener clickListener) {
if (clickListener == null)
throw new IllegalArgumentException("null runnable");
if (initialInterval < 0 || normalInterval < 0)
throw new IllegalArgumentException("negative interval");
this.initialInterval = initialInterval;
this.normalInterval = normalInterval;
this.clickListener = clickListener;
}
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()) {
case MotionEvent.ACTION_DOWN:
handler.removeCallbacks(handlerRunnable);
handler.postDelayed(handlerRunnable, initialInterval);
touchedView = view;
touchedView.setPressed(true);
clickListener.onClick(view);
return true;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
handler.removeCallbacks(handlerRunnable);
touchedView.setPressed(false);
touchedView = null;
return true;
}
return false;
}
}
Usage:
Button button = new Button(context);
button.setOnTouchListener(new RepeatListener(400, 100, new OnClickListener() {
@Override
public void onClick(View view) {
// the code to execute repeatedly
}
}));
Here is a simple class called AutoRepeatButton which can, in many instances, be used as a drop-in replacement for the standard Button class:
package com.yourdomain.yourlibrary;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
public class AutoRepeatButton extends Button {
private long initialRepeatDelay = 500;
private long repeatIntervalInMilliseconds = 100;
private Runnable repeatClickWhileButtonHeldRunnable = new Runnable() {
@Override
public void run() {
//Perform the present repetition of the click action provided by the user
// in setOnClickListener().
performClick();
//Schedule the next repetitions of the click action, using a faster repeat
// interval than the initial repeat delay interval.
postDelayed(repeatClickWhileButtonHeldRunnable, repeatIntervalInMilliseconds);
}
};
private void commonConstructorCode() {
this.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
int action = event.getAction();
if(action == MotionEvent.ACTION_DOWN)
{
//Just to be sure that we removed all callbacks,
// which should have occurred in the ACTION_UP
removeCallbacks(repeatClickWhileButtonHeldRunnable);
//Perform the default click action.
performClick();
//Schedule the start of repetitions after a one half second delay.
postDelayed(repeatClickWhileButtonHeldRunnable, initialRepeatDelay);
}
else if(action == MotionEvent.ACTION_UP) {
//Cancel any repetition in progress.
removeCallbacks(repeatClickWhileButtonHeldRunnable);
}
//Returning true here prevents performClick() from getting called
// in the usual manner, which would be redundant, given that we are
// already calling it above.
return true;
}
});
}
public AutoRepeatButton(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
commonConstructorCode();
}
public AutoRepeatButton(Context context, AttributeSet attrs) {
super(context, attrs);
commonConstructorCode();
}
public AutoRepeatButton(Context context) {
super(context);
commonConstructorCode();
}
}
Oliv's RepeatListenerClass is pretty good, but it does not handle "MotionEvent.ACTION_CANCEL", so handler does not remove call back in that action. This makes problems in PagerAdapter, and so on. So I added that event case.
private Rect rect; // Variable rect to hold the bounds of the view
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()) {
case MotionEvent.ACTION_DOWN:
handler.removeCallbacks(handlerRunnable);
handler.postDelayed(handlerRunnable, initialInterval);
downView = view;
rect = new Rect(view.getLeft(), view.getTop(), view.getRight(),
view.getBottom());
clickListener.onClick(view);
break;
case MotionEvent.ACTION_UP:
handler.removeCallbacks(handlerRunnable);
downView = null;
break;
case MotionEvent.ACTION_MOVE:
if (!rect.contains(view.getLeft() + (int) motionEvent.getX(),
view.getTop() + (int) motionEvent.getY())) {
// User moved outside bounds
handler.removeCallbacks(handlerRunnable);
downView = null;
Log.d(TAG, "ACTION_MOVE...OUTSIDE");
}
break;
case MotionEvent.ACTION_CANCEL:
handler.removeCallbacks(handlerRunnable);
downView = null;
break;
}
return false;
}
Your basic implementation is sound. However, I would encapsulate that logic into another class so that you can use it in other places without duplicating code. See e.g. this implementation of "RepeatListener" class that does the same thing you want to do, except for a seek bar.
Here's another thread with an alternative solution, but it's very similar to your first one.
Here's an answer based on Oliv's with the following tweaks:
- Instead of taking a click listener and calling
onClickdirectly, it callsperformClickorperformLongClickon the view. This will trigger standard clicking behavior, like haptic feedback on long click. - It can be configured to either fire the
onClickimmediately (like the original), or only onACTION_UPand only if no click events have fired (more like how standardonClickworks). - Alternate no-arg constructor that sets
immediateClickto false and uses the system-standard long press timeout for both intervals. To me this feels the most like what a standard "repeat long press" would be, if it existed.
Here it is:
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
/**
* A class that can be used as a TouchListener on any view (e.g. a Button).
* It either calls performClick once, or performLongClick repeatedly on an interval.
* The performClick can be fired either immediately or on ACTION_UP if no clicks have
* fired. The performLongClick is fired once after initialInterval and then repeatedly
* after normalInterval.
*
* <p>Interval is scheduled after the onClick completes, so it has to run fast.
* If it runs slow, it does not generate skipped onClicks.
*
* Based on http://stackoverflow.com/a/12795551/642160
*/
public class RepeatListener implements OnTouchListener {
private Handler handler = new Handler();
private final boolean immediateClick;
private final int initialInterval;
private final int normalInterval;
private boolean haveClicked;
private Runnable handlerRunnable = new Runnable() {
@Override
public void run() {
haveClicked = true;
handler.postDelayed(this, normalInterval);
downView.performLongClick();
}
};
private View downView;
/**
* @param immediateClick Whether to call onClick immediately, or only on ACTION_UP
* @param initialInterval The interval after first click event
* @param normalInterval The interval after second and subsequent click
* events
* @param clickListener The OnClickListener, that will be called
* periodically
*/
public RepeatListener(
boolean immediateClick,
int initialInterval,
int normalInterval)
{
if (initialInterval < 0 || normalInterval < 0)
throw new IllegalArgumentException("negative interval");
this.immediateClick = immediateClick;
this.initialInterval = initialInterval;
this.normalInterval = normalInterval;
}
/**
* Constructs a repeat-listener with the system standard long press time
* for both intervals, and no immediate click.
*/
public RepeatListener()
{
immediateClick = false;
initialInterval = android.view.ViewConfiguration.getLongPressTimeout();
normalInterval = initialInterval;
}
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()) {
case MotionEvent.ACTION_DOWN:
handler.removeCallbacks(handlerRunnable);
handler.postDelayed(handlerRunnable, initialInterval);
downView = view;
if (immediateClick)
downView.performClick();
haveClicked = immediateClick;
return true;
case MotionEvent.ACTION_UP:
// If we haven't clicked yet, click now
if (!haveClicked)
downView.performClick();
// Fall through
case MotionEvent.ACTION_CANCEL:
handler.removeCallbacks(handlerRunnable);
downView = null;
return true;
}
return false;
}
}