Android OnClickListener - identify a button
AndroidEventsResourcesListenerAndroid Problem Overview
I have the activity:
public class Mtest extends Activity {
Button b1;
Button b2;
public void onCreate(Bundle savedInstanceState) {
...
b1 = (Button) findViewById(R.id.b1);
b2 = (Button) findViewById(R.id.b2);
b1.setOnClickListener(myhandler);
b2.setOnClickListener(myhandler);
...
}
View.OnClickListener myhandler = new View.OnClickListener() {
public void onClick(View v) {
// MY QUESTION STARTS HERE!!!
// IF b1 do this
// IF b2 do this
// MY QUESTION ENDS HERE!!!
}
}
}
How do I check which button has been clicked?
Android Solutions
Solution 1 - Android
You will learn the way to do it, in an easy way, is:
public class Mtest extends Activity {
Button b1;
Button b2;
public void onCreate(Bundle savedInstanceState) {
...
b1 = (Button) findViewById(R.id.b1);
b2 = (Button) findViewById(R.id.b2);
b1.setOnClickListener(myhandler1);
b2.setOnClickListener(myhandler2);
...
}
View.OnClickListener myhandler1 = new View.OnClickListener() {
public void onClick(View v) {
// it was the 1st button
}
};
View.OnClickListener myhandler2 = new View.OnClickListener() {
public void onClick(View v) {
// it was the 2nd button
}
};
}
Or, if you are working with just one clicklistener, you can do:
View.OnClickListener myOnlyhandler = new View.OnClickListener() {
public void onClick(View v) {
switch(v.getId()) {
case R.id.b1:
// it was the first button
break;
case R.id.b2:
// it was the second button
break;
}
}
}
Though, I don't recommend doing it that way since you will have to add an if for each button you use. That's hard to maintain.
Solution 2 - Android
Or you can try the same but without listeners. On your button XML definition:
android:onClick="ButtonOnClick"
And in your code define the method ButtonOnClick:
public void ButtonOnClick(View v) {
switch (v.getId()) {
case R.id.button1:
doSomething1();
break;
case R.id.button2:
doSomething2();
break;
}
}
Solution 3 - Android
I prefer:
class MTest extends Activity implements OnClickListener {
public void onCreate(Bundle savedInstanceState) {
...
Button b1 = (Button) findViewById(R.id.b1);
Button b2 = (Button) findViewById(R.id.b2);
b1.setOnClickListener(this);
b2.setOnClickListener(this);
...
}
And then:
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.b1:
....
break;
case R.id.b2:
....
break;
}
}
Switch-case is easier to maintain than if-else, and this implementation doesn't require making many class variables.
Solution 4 - Android
Five Ways to Wire Up an Event Listener is a great article overviewing the various ways to set up a single event listener. Let me expand that here for multiple listeners.
- Member Class
public class main extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//attach an instance of HandleClick to the Button
HandleClick handleClick = new HandleClick();
findViewById(R.id.button1).setOnClickListener(handleClick);
findViewById(R.id.button2).setOnClickListener(handleClick);
}
private class HandleClick implements OnClickListener{
public void onClick(View view) {
switch(view.getId()) {
case R.id.button1:
// do stuff
break;
case R.id.button2:
// do stuff
break;
}
}
}
}
2. Interface Type
public class main extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.button1).setOnClickListener(handleClick);
findViewById(R.id.button2).setOnClickListener(handleClick);
}
private OnClickListener handleClick = new OnClickListener() {
public void onClick(View view) {
switch (view.getId()) {
case R.id.button1:
// do stuff
break;
case R.id.button2:
// do stuff
break;
}
}
};
}
3. Anonymous Inner Class
public class main extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.button1).setOnClickListener(new OnClickListener() {
public void onClick(View view) {
// do stuff
}
});
findViewById(R.id.button2).setOnClickListener(new OnClickListener() {
public void onClick(View view) {
// do stuff
}
});
}
}
4. Implementation in Activity
public class main extends Activity implements OnClickListener {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.button1).setOnClickListener(this);
findViewById(R.id.button2).setOnClickListener(this);
}
public void onClick(View view) {
switch (view.getId()) {
case R.id.button1:
// do stuff
break;
case R.id.button2:
// do stuff
break;
}
}
}
5. Attribute in View Layout for OnClick Events
public class main extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void HandleClick(View view) {
switch (view.getId()) {
case R.id.button1:
// do stuff
break;
case R.id.button2:
// do stuff
break;
}
}
}
And in xml:
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="HandleClick" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="HandleClick" />
Solution 5 - Android
Another way of doing it is a single listener from activity , like this:
public class MyActivity extends Activity implements OnClickListener {
....... code
//my listener
@Override
public void onClick(View v) {
if (v.getId() == R.id.mybutton) {
DoSomething();
return;
}
if (v.getId() == R.id.mybutton2) {
DoSomething2();
return;
}
}
}
I Like to do it with single IF instead of switch-else, but if you prefer that, then you should do:
//my listener
@Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.mybutton:
{
DoSomething();
break;
}
case R.id.mybutton2:
{
DoSomething();
break;
}
}
}
Solution 6 - Android
If you don't want to save instances of the 2 button in the class code, follow this BETTER way (this is more clear and fast!!) :
public void buttonPress(View v) {
switch (v.getId()) {
case R.id.button_one:
// do something
break;
case R.id.button_two:
// do something else
break;
case R.id.button_three:
// i'm lazy, do nothing
break;
}
}
Solution 7 - Android
The best way is by switch-ing between v.getId(). Having separate anonymous OnClickListener for each Button is taking up more memory. Casting View to Button is unnecessary. Using if-else when switch is possible is slower and harder to read. In Android's source you can often notice comparing the references by if-else:
if (b1 == v) {
// ...
} else if (b2 == v) {
I don't know exactly why they chose this way, but it works too.
Solution 8 - Android
use setTag();
like this:
@Override
public void onClick(View v) {
int tag = (Integer) v.getTag();
switch (tag) {
case 1:
System.out.println("button1 click");
break;
case 2:
System.out.println("button2 click");
break;
}
}
Solution 9 - Android
In addition to Cristian C's answer (sorry, I do not have the ability to make comments), if you make one handler for both buttons, you may directly compare v to b1 and b2, or if you want to compare by the ID, you do not need to cast v to Button (View has getId() method, too), and that way there is no worry of cast exception.
Solution 10 - Android
Button mybutton = new Button(ViewPagerSample.this);
mybutton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
});
Solution 11 - Android
Button button1 = (Button)findViewById(R.id.button1);
button1.setOnClickListener(this);
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(v.getId() == R.id.button1){
Toast.makeText(context, "Button 1 Click", Toast.LENGTH_LONG).show();
}
}