I want to make a simple button which will start to loop a function every period of time which I can set. But not only it will start the loop, but also stop the loop if I click the button again. Is there anyway I can achieve this with a single button?
2 Answers
Here's how I'd do it
public class MainActivity extends AppCompatActivity {
private Button btn;
private View.OnClickListener runOnClickListener;
private View.OnClickListener stopOnClickListener;
void init() {
Handler handler = new Handler();
int duration = 5000;
Runnable runnable = new Runnable() {
@Override
public void run() {
foo();
handler.postDelayed(this, duration);
}
};
runOnClickListener = view -> {
runnable.run();
btn.setOnClickListener(stopOnClickListener);
};
stopOnClickListener = view -> {
handler.removeCallbacks(runnable);
btn.setOnClickListener(runOnClickListener);
};
btn.setOnClickListener(runOnClickListener);
}
void foo() {
Log.i("foo", "foo");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn = findViewById(R.id.btn);
init();
}
}
3 Comments
Prototype7
runOnClickListener and stopOnClickListener gave me an error. Can you help me?
Cole Tustin
Could be because I'm using lambdas. Try using
new View.OnClickListener() in place of view ->Prototype7
Thank you so much! It works like a charm.
Yeah, give you a simple example.
First, create two constant values and one instance variable:
//indicate whether or not the loop is running
private boolean isRunning = false;
//used for handler to send empty msg
private final static int MSG_LOOP = 1;
private final static long LOOP_INTERVAL = 5000;
Then create a Handler instance to handle the loop logic:
Handler handler = new Handler() {
@Override
public void handleMessage(@NonNull Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case MSG_LOOP:
doStuff();
break;
}
}
};
private void doStuff() {
//after what you want to do is done, send another MSG_LOOP msg with delay
handler.sendEmptyMessageDelayed(MSG_LOOP, LOOP_INTERVAL);
}
And finally:
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isRunning) {
//cancel if any in the message queue
handler.removeMessages(MSG_LOOP);
} else {
//if you do not want to start the loop immediately, then use: "sendEmptyMessageDelayed"
handler.sendEmptyMessage(MSG_LOOP);
}
}
});
