Develop Reference

Duplicate method to log out

I'm a beginner and I have (I think) a simple question for you. I have a method used in every Activity except LoginActivity. It's opened when I click on the shutdown icon. This is code ->
public void logOut(MenuItem item) {
Intent intent = new Intent("THIS_CLASS".this, LoginActivity.class);
startActivity(intent);
}
but I do not want to duplicate it in every Activity, may exist any solution ? I am writing here because I can't find a solution on the Web. The problem is that I can not express my intentions in the question on the Internet. Every "duplicate method" gives answers not on the subject. I am not looking for complete code. I prefer only prompt.

Firstly, create a help class and add a static method like this:
import android.content.Context;
import android.content.Intent;
public class MyHelper {
public static void startActivityB(Context context) {
Intent intent = new Intent(context, LoginActivity.class);
context.startActivity(intent);
}
}
Then call the method and pass correct context like below:
findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
MyHelper.startActivityB(YourActivity.this);
}
});
Note: if MyHelper, LoginActivity,YourActivity are not in a same package, you should import corresponding package, that is an easy job.

It's not the best solution, but if you want a bunch of activities to share the same methods, then create a BaseActivity that they all extend from.
public abstract class BaseActivity extends Activity {
//... Shared stuff
protected void logOut() {
//Do some data cleaning and whatever else you need
Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
startActivity(intent);
}
}
public class MyActivity extends BaseActivity {
//... Main code
private void onLogOutClicked() {
logout();
}
}
Just make sure you clean out your authentication/session data when this occurs. Try to utilise inheritance for shared functionality.

Call Public void

I have a public void in one class and I want to call it in another class when it creates but nothing seems to be working. here is the code of my first activity
public class activityone extends Activity {
public void actionC() {
//actions
}
Does anyone know how to call it in my second class?

In general, you need to have an instance of your activityone class in order to call an instance method.
To create an instance, you generally use a constructor like:
activityone a = new activityone();
a.actionC();
I'm not sure this is what you want though, because Activitys are generally created by the Android system itself and you should handle the onCreate method instead.

Here is what you can do:
public class activityone extends Activity {
/*public void actionC() {*/ //Instead on normal method, write your actions in onCreate()
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//actions
}
and in your second activity, do this:
Intent intent = new Intent(getApplicationContext(),activityone.class);
startActivity(intent);
Hope it helps !!!

Trying to call an activity, but having troubles with onClick

im trying to run this simple code (im a beginner :).
trying to run this. the // text is usually what i use for buttons. however, i saw this switch technique that i wanted to try, it seemed more efficient. however, i get errors related to the onClick (something about the ( ) and that 'void is an invalid type'). i have no idea what can cause this. just wanna access the buttons. can anyone please tell me why?
Thanks!
package com.experiment.fewops;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class FewOptions extends Activity {
/** Called when the activity is first created. */
final Button sexy = (Button) findViewById(R.id.buttonSexy);
final Button text = (Button) findViewById(R.id.buttonText);
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// sexy.setOnClickListener(new View.OnClickListener() {
//
// #Override
// public void onClick(View v) {
// Intent intent = new Intent(this, SexyPage.class);
// startActivity(intent);
// }
// });
#Override
public void onClick(View v) {
switch(v.getId()){
case R.id.buttonSexy:
Intent intent = new Intent(this,SexyPage.class);
startActivity(intent);
break;
}
};
}
}

There are actually 2 problems here:
First, as #Saiesh said, if you want to implement the click listener at the class level, you need to change your class declaration to implment OnClickListener. So your declaration will look like
public class FewOptions extends Activity implements OnClickListener{
The second problem (and the reason you're getting the error about void being a bad type) is that you're declaring the onClick method in the body of your onCreate method. move the declaration of the onClick method outside the closing brace (}) of the onCreate method and that error should go away.
One more note: after you make the 2 fixes above, don't forget to add your class as the click listener for the button:
sexy.setOnClickListener(this);

You need to pass right context
Intent intent = new Intent(FewOptions.this,SexyPage.class);
FewOptions.this.startActivity(intent);

Well the solution is that to use this onClick() method your class needs to implement the onClickListener interface . Thus your class heading should be something like this
public class FewOptions extends Activity implements onClickListener
{
//Eclipse will automatically ask you to override the onClick() method
}
So thats the solution :)

Error while using PackageManager in Android

I got a problem in one Android Application which I am working in which I am getting error when I use PackageManager.
The Application is as follows:
Home.java
package com.main.home;
public class Home extends Activity
{
//onclicking a Button say "send"
send.onClickListener()
{
public void onClick() {
Intent i =new Intent();
i.setClassName("com.main.home", "com.main.home.home1");
startActivity(i);
}
}
Home1.java
package com.main.home;
import com.andr.resulting.Result ;
public class Home1 extends Activity {
EditText et=(EditText)findViewById(R.id.e1);
//Clicking on forwardButton in that onClick()
public void onClick()
{
String s[] = {e1.getText().toString(),""};
//Calling a method in a class Result of another package which is not activity
Result.finalfunc(Home1.this,s);
}
Result.java
package com.andr.resulting; //different package
public class Result {
public static void finalfunc(Activity act,String[] re) ...
//Here I want to get the details of this particular class's package (com.andr.resulting) using PackageManager
// I tried like this:
Result.this.getPackageManager().getApplicationInfo(Result.getPackageName(),0))
I am getting error getPackageManager() does not exists in this class file.
How do I solve this issue? I will be eagerly waiting for valuable reply.
Thanks in Advance.

try this::
this.getPackageManager().getApplicationInfo(this.getPackageName(), 0);

Result doesn't extend Context like your Activity class does. So the method isn't available in that class. You need to call act.getPackageManager() inside there instead of this.getPackageManager().

New Activity nullpointerexception

I have a beginners problem. Here is my situation:
I want to start a new activity from the main activity. The code to launch the new activity is found in a separate class file. I seem to be passing the wrong arguments and I am ending up in a nullpointerexception when trying to launch the new activity. The new activity launches fine when I place the code in the main activity class file, therefore the second activity and the manifest are fine. Here is a sample of my code:
In my main activity class where I instanciate the second class (THIS IS MY MAIN ACTIVITY. I OMITTED THE REST BECAUSE I DO NOT THINK IT IS RELATED TO THE PROBLEM):
Tester mytest = new Tester();
mytest.test(this);
In my second class file (THIS IS NOT AN ACTIVITY; IT IS A CLASS THAT IS INSTANTIATED IN THE ACTIVITY):
public class Tester extends Activity {
Intent myIntent;
public void test (Context context) {
myIntent = new Intent (Intent.ACTION_VIEW);
myIntent.setClass(context, newActivity.class);
thebutton.setOnClickListener(
new OnClickListener() {
public void onClick(View v) {
startActivity(myIntent);
}
}
):}
When I perform the click I receive a nullpointerexception at startactivity. Can anyone enlighten me on this please?I am sure that I am wrongly using the context.

Activities are started with Intents. Please read the Android Application Fundamentals first and try the Hello World app :)
I understood that you will use your separate Tester class at all cost ;) so I'm trying to adapt and help you out there.
First of all, don't let your class inherit from Activity. This won't help you, cause this calls will probably not have any valid context. Activity somehow implements the template pattern, providing you key method like onCreate(...), onPause(...) etc and is instantiated by the Android OS.
If you still want to use the class, you have to pass in the context. Probably you're aiming for some MVC/MVP pattern structure, anyway.
public class Tester {
private Context context;
public Tester(Context context){
this.context = context;
}
public void test () {
final Intent myIntent = new Intent(context, NewActivity.class);
//guess this comes from somewhere, hope through a findViewById method
thebutton.setOnClickListener(
new OnClickListener() {
public void onClick(View v) {
context.startActivity(myIntent);
}
}
)};
}
}
This would be a proposed solution from my side. A problem I still see here is on how you retrieve the button in that test() method. In order to have that work properly you have to retrieve it from some View class (with view.findViewByid(R.id.myButton)) or to create it dynamically and associate it with the view during the onCreate(...) of your Activity (probably using an Inflater).