Develop Reference

Set background of Activity from another one

I'm trying to set a background from ActivityB to AcitivtyA using getInstance but it only show me the Toast message, whenever turn back to ActivityA, there's no change.
I have this in my ActivityA:
private static MainActivity activityA;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
activityA = this;
}
public static MainActivity getInstance(){
return activityA;
}
public void setLeavesBackground() {
FrameLayout mainFrameLyt = (FrameLayout) findViewById(R.id.mainFrameLayout);
mainFrameLyt.setBackgroundColor(Color.parseColor("#00FF00"));
Toast.makeText(getBaseContext(), "New style applied", Toast.LENGTH_SHORT).show();
}
And this in my ActivityB:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_change_style);
ImageButton leavesBtn = (ImageButton) findViewById(R.id.leavesBtn);
leavesBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
MainActivity.getInstance().setLeavesBackground(); //call myFunction using activityA
}
});
}
What should I do?

You approach to get an Instance of another Activity and modify it from within another activity is wrong:
public static MainActivity getInstance(){
return activityA;
}
You have to obey the Activity lifecycle
A way how you could set another activities background is by creating a shared preferences value for the background color and use it in the onCreate method of your Activity.ñ

How to implement parent methods to activity and FragmentActivity?

I am working on an android application,
and I have number of activities that extend from a custom activity.
Now I created a new FragmentActivity and I need the same functions that I have implemented in my custom activity.
How can I do that?
Edit
This is an simple example
public class BaseActivity extends Activity
{
protected void someFunction()
{
Log.i("TEST","This is a test");
}
}
public class MainActivity extends BaseActivity
{
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
someFunction();
}
}
this is my FragmentActivity:
public class MyFragmentActivity extends FragmentActivity
{
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// here I want to use someFunction()..
}
}

In Java you can't extend more than one class.
So I guess you should extend BaseActivity from FragmentActivity instead of Activity

Want to Run a function without click any button when application start

I have a function named 'func()'. I want to run this function when application start without clicking any button. just when application load I want to show a massage.that massage in that function. I just want to run that function when app start what will be the code.
public class TextViewActivity extends Activity {
public static EditText etxt;
public final void func(){
etxt.setText("Massage");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
}
}

Just put a call to the function on the onCreate
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
func(); //A call to the function.
}
Hope that helps.

I don't recommend subclassing the Application in order to do this. When the application starts it will go to the main activity. So I would say just keep a SharedPreference boolean value if it has been set. If not show the message.
So keep state of the application here: http://developer.android.com/reference/android/content/SharedPreferences.html, just set a boolean. Remember when you app gets called, the activity onCreate always gets called of the main activity, so its just a matter of not calling it again.

try using below code.. you need to call ur function after you initialize edittext etxt. so it can not cause you NPE
public final void func(){
etxt.setText("Message");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
func();// here your function call.
}

Try this:
public class TextViewActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.etxt2).setText("SMTH");
}
}
In case you really need a function to be called, you can use this:
public class TextViewActivity extends Activity {
public final void func() {
findViewById(R.id.etxt2).setText("SMTH");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
func();
}
}

How to call function of one activity from another activity

Actually i want to call a function of one activity from another activity..i write a simple code for that but its not working..and show runtime error..please check the code...if there any mistake..
code for activity1:
public class Activity1 extends Activity2
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main2);
call();
}
public void call()
{
showToast("Helloo");
}
}
code for activity2:
public class Activity2 extends Activity
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void showToast(String s)
{
EditText t=(EditText)findViewById(R.id.editText1);
t.setText(s);
}
}

Your problem is that you're calling findViewById on a view that doesn't exist.
Activity1 is extending Activity2.
You call the super.onCreate in Activity1 which calls the onCreate in Activity2 which calls setContentView() for R.layout.main.
I'm guessing your text R.id.editText1 is in the main layout.
When Activity1 returns from the call to super.onCreate it immediately resets the content layout to main2.
The edit text box that you are trying to edit no longer exists. findViewById can not find it because the layout is not active. Thus it crashes.
To fix it try this:
public class Activity1 extends Activity2
{
private EditText et;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main2);
et = (EditText) findViewById(R.id.editText2);
call();
}
public void call()
{
showToast("Helloo", et);
}
}
Where R.id.editText2 is an edit text box in the layout main2.
In Activity2:
public class Activity2 extends Activity
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void showToast(String s, EditText t)
{
t.setText(s);
}
}

First, this is a bad design principle since only one Activity is active at a time. You can make a method static and then you can cross call them but at that point it should be in some sort of common util class.

The simplest way is to declare your showToast() method as public static, this way you can call it without having an instance of Activity2.

if you put it in as static you should declare it on your main activity

How to destroy an activity in Android?

While the application is running, I press the HOME button to close the application. When I start the application again, it resumes on the page displayed prior to clicking on HOME. I want the application to start with the initial display instead. I have used finish() to finish the activity but it is not working. Any suggestions?

Most likely you have several instances of the same activity. To resolve this kind of issues create your own parent Activity class e.g. MyRootActivity which will hold static list of all of available/alive activities:
public class MyRootActivity extends Activity
{
private static final String TAG=MyRootActivity.class.getName();
private static ArrayList<Activity> activities=new ArrayList<Activity>();
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
activities.add(this);
}
#Override
public void onDestroy()
{
super.onDestroy();
activities.remove(this);
}
public static void finishAll()
{
for(Activity activity:activities)
activity.finish();
}
}
For that all of your activities need to be children of MyRootActivity.
Then when you are about to sure that you're closing your application - just call MyRootActivity.finishAll();

Create a static Activity object which activity finish on other activity and assign activity in this i.e you can can add more activities
public class demoActivity extends AppCompatActivity {
public static Activity self_intent;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.demo_activity);
selfintent=this;
}
//Other functions--------------
}
do same for other activities
on other
public class finishingActivity extends AppCompatActivity {
public Button activityCloseBtn;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.finishing_activity);
activityCloseBtn= (Button) view.findViewById(R.id.activity_close_btn);
activityCloseBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
demoActivity.selfintent.finish(); //for finish demoActivityactivity
//for other activities Activity.selfintent.finish();
finish(); //for finish current activity
}
});

try calling super.onPause() first and later call finish() inside your onPause() stub