So I have done some research, and after defining you button as an object by the code
private Button buttonname;
buttonname = (Button) findViewById(R.id.buttonnameinandroid) ;
here is my problem
buttonname.setOnClickListener(this); //as I understand it, the "**this**" denotes the current `view(focus)` in the android program
then your OnClick()
event...
Problem:
When I type in the "this", it says:
setOnClickListener (Android.View.view.OnClickListener) in View cannot be applied to (com.helloandroidstudio.MainActivity)
I have no idea why?
here is the code from the .java file
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
private Button btnClick;
private EditText Name, Date;
private TextView msg, NameOut, DateOut;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btnClick = (Button) findViewById(R.id.button) ;
btnClick.setOnClickListener(this);
Name = (EditText) findViewById(R.id.textenter) ;
Date = (EditText) findViewById(R.id.editText) ;
msg = (TextView) findViewById(R.id.txtviewOut) ;
NameOut = (TextView) findViewById(R.id.txtoutName) ;
DateOut = (TextView) findViewById(R.id.txtOutDate) ;
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
}
public void onClick(View v)
{
if (v == btnClick)
{
if (Name.equals("") == false && Date.equals("") == false)
{
NameOut = Name;
DateOut = Date;
msg.setVisibility(View.VISIBLE);
}
else
{
msg.setText("Please complete both fields");
msg.setVisibility(View.VISIBLE);
}
}
return;
}
SetOnClickListener (Android.View.view.OnClickListener) in View cannot be applied to (com.helloandroidstudio.MainActivity)
This means in other words (due to your current scenario) that your MainActivity need to implement OnClickListener :
public class Main extends ActionBarActivity implements View.OnClickListener {
// do your stuff
}
This:
buttonname.setOnClickListener(this);
means that you want to assign listener for your Button "on this instance" ->
this instance represents OnClickListener and for this reason your class have to implement that interface.
It's similar with anonymous listener class (that you can also use):
buttonname.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
}
});
Button button= (Button)findViewById(R.id.buttonId);
button.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
// click handling code
}
});
package com.mani.smsdetect;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity implements View.OnClickListener {
//Declaration Button
Button btnClickMe;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Intialization Button
btnClickMe = (Button) findViewById(R.id.btnClickMe);
btnClickMe.setOnClickListener(MainActivity.this);
//Here MainActivity.this is a Current Class Reference (context)
}
@Override
public void onClick(View v) {
//Your Logic
}
}
When you define an OnClickListener
(or any listener) this way
btnClick.setOnClickListener(this);
you need to implement
the OnClickListener
in your Activity
.
public class MainActivity extends ActionBarActivity implements OnClickListener{
public class MainActivity extends AppCompatActivity implements View.OnClickListener
Whenever you use (this) on click events, your main activity has to implement ocClickListener. Android Studio does it for you, press alt+enter on the 'this' word.
package com.mani.helloworldapplication;
import android.app.Activity;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements View.OnClickListener {
//Declaration
TextView tvName;
Button btnShow;
@Override
protected void onCreate(Bundle savedInstanceState) {
//Empty Window
super.onCreate(savedInstanceState);
//Load XML File
setContentView(R.layout.activity_main);
//Intilization
tvName = (TextView) findViewById(R.id.tvName);
btnShow = (Button) findViewById(R.id.btnShow);
btnShow.setOnClickListener(this);
}
@Override
public void onClick(View v)
{
String name = tvName.getText().toString();
Toast.makeText(MainActivity.this,name,Toast.LENGTH_SHORT).show();
}
}
Start your OnClickListener, but when you get to the first set up parenthesis, type new, then View, and press enter. Should look like this when you're done:
Button btn1 = (Button)findViewById(R.id.button1);
btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//your stuff here.
}
});
//as I understand it, the "this" denotes the current view(focus) in the android program
No, "this" will only work if your MainActivity
referenced by this
implements the View.OnClickListener
, which is the parameter type for the setOnClickListener()
method. It means that you should implement View.OnClickListener
in MainActivity
.
public class MainActivity extends Activity {
Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.submitButton);
button.setOnClickListener(new MyClass());
}
public class MyClass implements View.OnClickListener {
@Override
public void onClick(View v) {
}
}
}
I found a video. This video guides clearly about the handling a button click. And now, I knew that there are three ways to handle event click on View in Android.
You can simply set onClickListener on a Button or anything using Lambda Expression which looks like
private Button buttonname;
buttonname = (Button)findViewById(R.id.buttonnameinandroid);
buttonname.setOnClickListener(v ->
{
//Your Listener Code Here
});
in Activity java class you would need a method first to find the view of the button as :
btnSum =(Button)findViewById(R.id.button);
after this set on click listener
btnSum.setOnClickListener(new View.OnClickListener() {
and override onClick method for your functionality .I have found a fully working example here : http://javainhouse.blogspot.in/2016/01/button-example-android-studio.html
Your Activity
must implement View.OnClickListener
, like this:
public class MainActivity extends
Activity implements View.OnClickListener{
// YOUR CODE
}
And inside MainActivity
override the method onClick()
, like this:
@override
public void onClick (View view){
//here YOUR Action response to Click Button
}
You need to do nothing but, just type new View.OnClickListener()
in your btnClick.setOnClickListener()
. I mean you have to type btnClick.setOnClickListener(new View.onClickListener
the bracket will remain open, just hit enter then a method will be created like this,
btnClick.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
}
});
It's just mean that you are creating a new view of OnClickListener and passing a view as it's a parameter. Now you can do whatever u were supposed to do, in that onClick(View v) method.
Different ways to handle button event
Button btn1 = (Button)findViewById(R.id.button1);
btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(context, "Button 1",
Toast.LENGTH_LONG).show();
}
});
[Check this article for more details about button event handlers]
public class EditProfile extends AppCompatActivity {
Button searchBtn;
EditText userName_editText;
EditText password_editText;
EditText dob_editText;
RadioGroup genderRadioGroup;
RadioButton genderRadioBtn;
Button editBtn;
Button deleteBtn;
Intent intent;
DBHandler dbHandler;
public static final String USERID_EDITPROFILE = "userID";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_profile);
searchBtn = (Button)findViewById(R.id.editprof_searchbtn);
userName_editText = (EditText)findViewById(R.id.editprof_userName);
password_editText = (EditText)findViewById(R.id.editprof_password);
dob_editText = (EditText)findViewById(R.id.editprof_dob);
genderRadioGroup = (RadioGroup)findViewById(R.id.editprof_radiogroup);
editBtn = (Button)findViewById(R.id.editprof_editbtn);
deleteBtn = (Button)findViewById(R.id.editprof_deletebtn);
intent = getIntent();
dbHandler = new DBHandler(EditProfile.this);
setUserDetails();
deleteBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String username = userName_editText.getText().toString();
if(username == null){
Toast.makeText(EditProfile.this,"Please enter username to delete your profile",Toast.LENGTH_SHORT).show();
}
else{
UserProfile.Users users = dbHandler.readAllInfor(username);
if(users == null){
Toast.makeText(EditProfile.this,"No profile found from this username, please enter valid username",Toast.LENGTH_SHORT).show();
}
else{
dbHandler.deleteInfo(username);
Intent redirectintent_home = new Intent("com.modelpaper.mad.it17121002.Home");
startActivity(redirectintent_home);
}
}
}
});
editBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String userID_String = intent.getStringExtra(Home.USERID);
if(userID_String == null){
Toast.makeText(EditProfile.this,"Error!!",Toast.LENGTH_SHORT).show();
Intent redirectintent_home = new Intent(getApplicationContext(),Home.class);
startActivity(redirectintent_home);
}
int userID = Integer.parseInt(userID_String);
String username = userName_editText.getText().toString();
String password = password_editText.getText().toString();
String dob = dob_editText.getText().toString();
int selectedGender = genderRadioGroup.getCheckedRadioButtonId();
genderRadioBtn = (RadioButton)findViewById(selectedGender);
String gender = genderRadioBtn.getText().toString();
UserProfile.Users users = UserProfile.getProfile().getUser();
users.setUsername(username);
users.setPassword(password);
users.setDob(dob);
users.setGender(gender);
users.setId(userID);
dbHandler.updateInfor(users);
Toast.makeText(EditProfile.this,"Updated Successfully",Toast.LENGTH_SHORT).show();
Intent redirectintent_home = new Intent(getApplicationContext(),Home.class);
startActivity(redirectintent_home);
}
});
searchBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String username = userName_editText.getText().toString();
if (username == null){
Toast.makeText(EditProfile.this,"Please enter a username",Toast.LENGTH_SHORT).show();
}
else{
UserProfile.Users users_search = dbHandler.readAllInfor(username);
if(users_search == null){
Toast.makeText(EditProfile.this,"Please enter a valid username",Toast.LENGTH_SHORT).show();
}
else{
userName_editText.setText(users_search.getUsername());
password_editText.setText(users_search.getPassword());
dob_editText.setText(users_search.getDob());
int id = users_search.getId();
Intent redirectintent = new Intent("com.modelpaper.mad.it17121002.EditProfile");
redirectintent.putExtra(USERID_EDITPROFILE,Integer.toString(id));
startActivity(redirectintent);
}
}
}
});
}
public void setUserDetails(){
String userID_String = intent.getStringExtra(Home.USERID);
if(userID_String == null){
Toast.makeText(EditProfile.this,"Error!!",Toast.LENGTH_SHORT).show();
Intent redirectintent_home = new Intent("com.modelpaper.mad.it17121002.Home");
startActivity(redirectintent_home);
}
int userID = Integer.parseInt(userID_String);
UserProfile.Users users = dbHandler.readAllInfor(userID);
userName_editText.setText(users.getUsername());
password_editText.setText(users.getPassword());
dob_editText.setText(users.getDob());
}
}
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