I am trying to go to second activity using button. Here is the code:
public class MainActivity extends AppCompatActivity {
Button login;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
login=(Button) findViewById(R.id.login);
login.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v) {
Intent i=new Intent();
i.setClassName(this,"com.example.ankit.layouts.SecondAtivity");
}
});
}
}
I am getting an error in i.setClassName() as "cannot resolve this method", but when I use MainActivity.this I do not get any error. Why does this happen?
this does not work because you are in an anonymous class of type OnClickListener which is not what setClassName expect. When you are writing MainActivity.this you are explicitly telling java to take the this from the encapsulating class of type MainActivity.
Use the following code
login.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v) {
Intent i=new Intent(MainActivity.this,SecondAtivity.class);
startActivity(i);
}
});
Related
I am new to Android Development and I found that while using the setOnClickListener() Method the onClick function takes a parameter instead of an argument. why is onClick function's syntax is like user defined function? I am very much confused. Below is an image that reflects my point of view.
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView display = findViewById(R.id.Display);
Button button = findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
display.setText("Ravikiran");
}
});
}
}
Here in the above code i am confused with the part of the code which is mentioned below.
public void onClick(View v) {
display.setText("Ravikiran");
}
I am trying to make a button in activity2(settings page), when the button is clicked, then the title of activity1(MainActivity) will change to what I set to. I have been trying to use interface to carry out the function but it gives me a null pointer exception error.
MainActivity
#Override
public void changeActionBarTitle(String editText){
actionTitle = editText;
setTitle(actionTitle);
};
Interface
public interface ActionBarInterface {
void changeActionBarTitle(String editText);
}
Setting page (activity 2)
public class SettingsPage extends AppCompatActivity {
ActionBarInterface actionBarInterface;
Button editCompanyNameButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings_page);
setTitle("Settings");
editCompanyNameButton = findViewById(R.id.editCompanyNameButton);
editCompanyNameButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
actionBarInterface.changeActionBarTitle("test");
}
});
}
}
Thanks.
You can try this code without using the interface
MainActivity:
#Override
protected void onResume() {
setTitle(Main2Activity.title);
super.onResume();
}
activity2:
public class SettingsPage extends AppCompatActivity {
Button editCompanyNameButton;
static String title;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
setTitle("Settings");
editCompanyNameButton = findViewById(R.id.editCompanyNameButton);
editCompanyNameButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
title = "test";
}
});
}
}
It gives a null pointer exception error because actionBarInterface was not initialised.
Check out topics on 'Getting a Result from an Activity', making use of classes and functions such as Intent, startActivityForResult, onActivityResult.
Android: how to make an activity return results to the activity which calls it?
I'm super new in Java! Pardon for this question although there are similar ones but I'm completely clueless on fixing my problem.
I'm trying to set an OnClickListener for each ImageButton to open a new activity.
The first ImageButton works but not for the subsequent ones, it is unclickable in AVD.
Would greatly appreciate some help on it!
public class CharacterSelect extends AppCompatActivity {
ImageButton arrowbtnright;
ImageButton contchibtn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_character_select);
arrowbtnright = (ImageButton) findViewById(R.id.arrowbtnright);
contchibtn = (ImageButton) findViewById(R.id.contchibtn);
arrowbtnright.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(CharacterSelect.this, CharacterSelect2.class));
contchibtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(CharacterSelect.this, MiniChallenge1.class));
}
});
}
});
}
You are currently adding the listener of the second button, from inside the listener of the first button, this is probably not what you want to do .
Try putting both at the same level, i.e :
arrowbtnright.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(final View v) {
startActivity(new Intent(CharacterSelect.this, CharacterSelect2.class));
}
});
contchibtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(final View v) {
startActivity(new Intent(CharacterSelect.this, MiniChallenge1.class));
}
});
I am trying to make a mobile application,but when ever i try to press the button i get a crash. The button should take me to a new activity page, i have already connect the other pages with the button in a right way. i am just wondering if this code is correct or not:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onButtonClick(View v)
{
Button a1= (Button) findViewById(R.id.button);
a1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SecondPage.class);
startActivity(intent);
}
});
}
public void onButtonClick1(View c)
{
Button a1= (Button) findViewById(R.id.button2);
a1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, ThirdPage.class);
startActivity(intent);
}
});
}
public void onButtonClick2(View d)
{
Button a1= (Button) findViewById(R.id.button3);
a1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, FourthPage.class);
startActivity(intent);
}
});
}
public void onButtonClick3(View f)
{
Button a1= (Button) findViewById(R.id.button4);
a1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, FifthPage.class);
startActivity(intent);
}
});
}
}
i just learned java from some videos in the youtube,so i am not sure if i did the activity function well or not. Thank you
There can be few reasons after it
1) Make sure you defined activity in Manifest file
2) check for android:onClick="" in xml file..
OR
Try Binding Buttons in onCreate() method.
and You can simply use this for onClick
a1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SecondPage.class);
startActivity(intent);
}
});
Remove onClick attribute in your activity_main.xml file and copy and past this code in your MainActivity.java file
public class MainActivity extends AppCompatActivity {
Button b1,b2,b3,b4;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1= (Button) findViewById(R.id.button);
b2= (Button) findViewById(R.id.button2);
b3= (Button) findViewById(R.id.button3);
b4= (Button) findViewById(R.id.button4);
b1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SecondPage.class);
startActivity(intent);
}
});
b2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, ThirdPage.class);
startActivity(intent);
}
});
b3.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, FourthPage.class);
startActivity(intent);
}
});
b4.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, FifthPage.class);
startActivity(intent);
}
});
}
}
If you are using the onclick attribute in layout XML then you doesn't need to set the onclick listener. If you are not using onclick then you need to set click listener. In your case your case, I think use are using onclick attribute in layout XML and also trying to set the click listener in using java code. so you need to either use onclick attribute in layout XML or use setOnCliickListener() in java code
I've just started to learn Java and I've been stumped on adding the code for a second button in an activity. I apologize for my (possible dumb question) and any wrong terminology.
Here is the MainActivity Java code:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnGo = (Button) findViewById(R.id.btnGo);
btnGo.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, GoActivity.class));
}
});
}
}
How can I add to this code for btnEscape to go to EscapeActivity?
You just have to do exacly the same thing you do with btnGo - this is find your button by id, and then set clickListener to it. It could looks like that:
Button btnEscape = (Button) findViewById(R.id.btnEscape);
btnEscape.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, EscapeActivity.class));
}
});
The optimised way to do that is implement your class with View.OnClickListener and override the method onClick and inside it use switch cases to switch between views and apply on clicks like this:
public class SampleActivity extends AppCompatActivity implements View.OnClickListener{
Button btnGo,btnEscape;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnGo = (Button) findViewById(R.id.btnGo);
btnEscape= (Button) findViewById(R.id.btnEscape);
btnGo.setOnClickListener(this);
btnEscape.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch (v.getId()){
case R.id.btnGo:
startActivity(new Intent(MainActivity.this, GoActivity.class));
break;
case R.id.btnEscape:
startActivity(new Intent(MainActivity.this, EscapeActivity.class));
break;
default:
break;
}
}
}
In code, what the two comments by Shiram and Nik above are saying is to add the block below that begins Button btnEscape... after Button btnGo.setOnclick's block.
#Override
protected void onCreate(Bundle savedInstanceState) {
...
Button btnGo = (Button) findViewById(R.id.btnGo);
...
Button btnEscape = (Button) findViewById(R.id.<<name of button in xml>>);
btnEscape.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
... whatever ... }
});
}
In short, the following is a really good pattern to have at your fingertips:
Button btn___ = (Button) findViewById(R.id.<<name of button in xml>>);
btn___.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
... whatever ... }
});