I'm using Eclipse for windows 7 and I am making an informative application(just text and offline content).
In my app I have about 180 buttons. Each button will lead to another screen. I need to know how to make each button lead to a specific screen?
And also, is there a way to like duplicate the code and not spend hours copying and pasting the code 180 times?
Check my code below for the first two screens:
That's for the MainActivity.java:
public void addListenerOnButton() {
final Context context = this;
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
}
});
}
I mean that code is only for one single button. Am I supposed to repeat this for every single button?
and also a question, how many classes should I do? 180 main activities, 180 fragment_main.xml and 180 activity_main.xml?
That's my idea, since your application is just a "informative application" you can create two activities:
Main activity with buttons
"Information page"
To do it i need info about how you get this informations:
In a SQLite Database.
In a string-array
Personally, i prefer a SQLite DB it allows you to improve it without problems in the future.
About the Information activity:
Example: in your layout you have a TextView where will be added the text which this activity should be passed.
To make it dynamic in your case we pass the string to show using Intents, in our onCreate we add something like this:
Intent intent = getIntents();
String stringToDisplay = null;
if (intent != null)
{
stringToDisplay = intent.getStringExtra (EXTRA_STRING_CONTENT);
}
getIntents will get the Intent object which is created and passed to it by our main activity. getStringExtra is a simple method which says to Android: i want to get the string which is saved with the key EXTRA_STRING_CONTENT (it's something like a Map)
EXTRA_STRING_CONTENT is a field which we used to make sure we don't make any error in passing data, since we need to use the same name when we pass it (in MainActivity) and when we read it (InformationActivity)
public static final String EXTRA_STRING_CONTENT = "EXTRA_STRING_CONTENT";
Ok, we are done.
We now only need to set the string to our TextView:
TextView infoTextView = (TextView) findViewById(R.id.infotextview);
infoTextView.setText (stringToDisplay);
Stop it.
Now we should go to our MainActivity code and modify our addListenerOnButton
final Context context = this;
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
}
});
Well, i will focus on this two lines
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
We need to pass the string to display here, how?
Before we used getStringExtra now it's similar (note: it's the same Intent class) but now we need the putExtra method, the compiler will select the correct overload for us so we just need to do
String stringToDisplay = "Hello world";
intent.putExtra(InformativeActivity.EXTRA_STRING_CONTENT, stringToDisplay);
(Note: InformativeActivity.EXTRA_STRING_CONTENT)
With the current code we will always sent Hello world to the second activity but we need something of dynamic based on the button... well now this depends on how you get the data.
If it's a string-array, you can save the string-array in an array and then based on the button (if it's the first sent string index 0, etc.).
An example:
int buttonId = 1; // it will be a general variable, if it's button 1 it will be 0, if 2-1 etc.
String[] informations = getResources().getStringArray(R.array.infos); // in a real code you should move it outside the `onClick` code and put it in a static final field.
intent.putExtra(InformativeActivity.EXTRA_STRING_CONTENT, informations[buttonId]); // it's the same of above
If you understand the concept you will know how to adapt the code based on your needs.
There are some cases where you need more info or what you want to sent is something which is better if managed by the second activity (example: in a sqlite database you could sent only the id of the line and read lines in the second activity based on this id)
Some things which you could change:
Avoid to call it MainActivity2, it's not so helpful as name
You don't need really to save Context, you could just use MainActivity.this
Try to make your addListenerOnButton more general, example take as argument a Button and set the listener to it.. don't read it from XML you will end up with 180 methods for every button.
Related
Consider you have a Button A and button B both of them when clicked it start Activity1 which contains only one TextView.
Now When I click on Button A it should start Activity1 and setTextView to "The click was from A"
and when clicked on B it should set the text to "The click was from B".
So I figure out that by making a global Boolean variable but I wanted to know is there any other way that is more efficient than making a global Boolean variable(the code become really messy with Boolean)
And this all is just an example in reality I want to add a lot of code instead of just setting the text.
TL;DR
Pass arguments with your Intent object that launches Activity2. Use putExtra methods. That is the default way of passing small pieces of data.
Explained
"making a global Boolean variable" is a bad solution (nothing personal, it just does not fit the given problem) in this situation as anyone has access to that variable and the value can be changed at any point in time making it unreliable.
When you launch activity with Intent you can use putExtra methods on it (example of such method in docs).
For example, there is a putExtra that accepts boolean as a value: link. Using that method you can remove the global variable, but the code still could be messy.
If this boolean variable is simply deciding which label to show you can pass the label itself using these putExtra methods. It would look like this:
// From Activity1 when you click Button A
buttonA.setOnClickListener {
Intent intent = new Intent(Activity1.this, Activity2.class);
intent.putExtra(Activity2.SOME_KEY, "This label is from buttonA.");
startActivity(intent);
}
// From Activity1 when you click Button B
buttonB.setOnClickListener {
Intent intent = new Intent(Activity1.this, Activity2.class);
intent.putExtra(Activity2.SOME_KEY, "This label is from buttonB. A slightly different one.");
startActivity(intent);
}
Activity2.SOME_KEY is some public static variable that you should declare to be sure that you use the same key for setting and getting back the value. You can name it differently. It must be of String type. There is no need to declare it in Activity2 class but since it is the key for passing arguments for Activity2 only I think that is the most fitting place.
And now in you can get that value back in Activity2:
class Activity2 extends Activity {
public static String SOME_KEY = "some string value";
private String labelValue = "";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
labelValue = getIntent().getStringExtra(SOME_KEY);
// ... other stuff here like setContentView
// use `labelValue` to set text into some TextView.
}
}
Currently i managed to create the buttons dynamically on a view
Here is the my code to create the buttons;
public void Add_on(View v) {
AlertDialog.Builder mbuilder = new AlertDialog.Builder(Mb.this);
View mview = getLayoutInflater().inflate(R.layout.activity_mb1, null);
EditText number = (EditText) mview.findViewById(R.id.etnum);
Button Create = (Button) mview.findViewById(R.id.etcreate);
Button Cancel = (Button) mview.findViewById(R.id.etcancel);
Create.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
if (!number.getText().toString().isEmpty())
{
Toast.makeText(Mb.this, "Number can be NULL",Toast.LENGTH_SHORT).show();
LinearLayout yenilayout = new LinearLayout(Mb.this);
int n =1;
for(int i=0; i<n; i++)
{
Button yeniButton = new Button(Mb.this);
yenilayout.addView(yeniButton);
yeniButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(Mb.this, "Button is working",Toast.LENGTH_SHORT).show();
}
});
}
altlayout.addView(yenilayout);
} else {
Toast.makeText(Mb.this, "Number cannot be NULL",Toast.LENGTH_SHORT).show();
}
}
});
But whenever i recall the activity, the buttons are no longer exist. So May i know can i place the button there permanently?
Thank you for suggestions
You can use Bundle to save an activity's state and recreate it in the onCreate() method. This works for a particular instance of Activity, so can be used to save data concerning selection, or user input etc., but not data that you need to be persistent across application launches.
To use the Bundle, override the onSaveInstanceState(Bundle) and onRestoreInstanceState(Bundle) methods in the Activity class. You can use methods from Bundle to save whatever data you like in a map, and get it back in onRestoreInstanceState(Bundle), which is called in onStart().
The default implementations already handle most UI stuff though, and I would have thought this would keep track of your buttons for you, so it may be that your question is actually about associating some persistent data with your application. (this also means that if you do override the above methods, you should make sure to call the super methods in the first line of your implementation).
If you need persistent data across application launches, then the quickest and easiest way would be to use SharedPreferences, see this answer for an example.
I was wondering if anyone could tell me how I could check a checkBox in an activity from another activity.
I'm making a homework app and I want to put a check next to the questions that have been completed.
So the first activity has a list of questions and next to them are unchecked boxes. When you click a question, the app takes you to the second activity. In the second activity, I want to check the box of the question that was completed.
You should use SharedPreferences for that. call this in the first activity:
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
prefs.putBoolean("KEY", <your value>).apply();
and something similar in another activity:
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
boolean isTicked = prefs.getBoolean("KEY", <default boolean value>);
where KEY can be anything, for example, your question's number
You should use intent and bundle logic for passing data between activities.(in most cases)
In the first activity, whenever you are creating the second activity, you pass your data.
Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
intent.putExtra("checked",checkBox.isChecked());
startActivity(intent);
In the second activity you receive your data by using :
Intent receivedIntent = getIntent();
boolean finalChecked = receivedIntent.getExtras().getBoolean("checked");
//now you can apply your logic with finalChecked variable
You can save checked check question to a bundle and pass it as extra to your second activity through intent and read it from that intent inside your second activity
In your first activity do something like this
public class FirstActivity extends Activity {
public static final String EXTRA_CHECKED_QUESTION = "Checked Question";
// other codes here
private void startSecondActivity() {
String checkedQuestion = getCheckedQuestion(); // a method to get checked question
Intent intent = new Intent(this, SecondActivity.class);
intent.putExtra(FirstActivity.EXTRA_CHECKED_QUESTION, checkedQuestion);
startActivity(intent);
}
}
then in your second activity
public class SecondActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstance) {
// other codes
String checkedQuestion = getIntent().getStringExtra(FirstActivity.EXTRA_CHECKED_QUESTION);
// do whatever you want with checkQuestion
}
}
Please note that the string which you pass as first parameter to putExtra() method in FirstActivity, should be same as the string you are using with getStringExtra() to retrieve your extra in SecondActivity, otherwise you can not retrieve your passed extra in SecondActivity.
Also, I did not write these codes inside idea, so there might be syntax error
Read more about intent here
I am new to android and am working on a fairly basic android application where users are able to create items that are added to a ListView. On creation of each item I create a instance of the 'clicker' class which keeps track of each items name/tick count/other statistics.
when on of the items in the list are clicked it launches a general activity, used by all of the items. I pass the 'clicker' class object to the activity so that it may construct initialize the textviews.
This is what happens when a list item is clicked (the clicker instances are created in a hashmap named clickers, so I first retrieve the key, then call clickers.get(key))
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
// pass along some ID so that the new activity can retrieve info
String clickedName = clickerListItems.get(arg2);
Intent intent = new Intent(MainActivity.this, ClickerActivity.class);
intent.putExtra("clickerName", clickers.get(clickedName));
startActivity(intent);
}
This is how the general activity receives the info
public class ClickerActivity extends Activity {
protected Clicker currentClicker;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_clicker);
Intent i = getIntent();
currentClicker = (Clicker) i.getSerializableExtra("clickerName");
TextView clickerHeader = (TextView) findViewById(R.id.clickerHeader);
clickerHeader.setText(currentClicker.getName());
final TextView countDisplay = (TextView) findViewById(R.id.countText);
countDisplay.setText(Integer.toString(currentClicker.getCount()));
final Button incrementButton = (Button) findViewById(R.id.incrementButton);
final Button resetButton = (Button) findViewById(R.id.resetButton);
(continues)
here's what the general activity looks like to add some perspective. It's fairly plain right now seeing as I am just starting out.
The issue is that say I click on item A of the ListView and increment it's counter (one of the stats) and then press the back button to return to the List Activity. Now if I click on the same listitem to reload the activity none of the data seems to have been saved. Is the clicker class instance not actually being altered? How do I save the info or restore the info? I would do something onRestoreInstanceState but since this is an activity that may be loaded by any item in the list that wouldn't work, right?
If there any clarification is required please let me know, thank you.
You can use shared preferences, to preserve those values.
http://developer.android.com/reference/android/content/SharedPreferences.html
By using this, none of your data will be lost. Just make sure that when you are starting the app again after killing it, you reset the values stored, so that your values are saved for activity relaunch, but not for app relaunch (unless you want it for that too).
EDIT: You can also put all your main code into an Asynctask(), so that processing would be done in the background and it would be kept alive even when you come out of the app.
Hi in my app i have placed two edit boxes and on OK button. In the edit boxes i am getting the values such as the first name and second name.
Now i want to do the following process
1. When i click the button OK i move over to the new page, here i want to display the data's entered in the edit boxes of the first page.
2.In the title bar of the second page i want display the data entered in the first edit box ie the first name entered there must be the title of the second page.
how to do this pls help me
Set the OK Button to have an OnClickListener
public void onCreate(Bundle savedInstanceState) {
View okButton = findViewById(R.id.okButtonImg); //assume you are using custom img for OK
okButton.setOnClickListener(okButtonListener);
}
In the Click Listener invoke an Intent.
In the Intent you can pass information using "putExtra"
private OnClickListener okButtonListener = new OnClickListener() {
public void onClick(View v) {
Intent secondPageIntent = new Intent(getBaseContext(), SecondPage.class);
secondPageIntent.putExtra("PASSVALUE","ANY STRING HERE");
startActivity(secondPageIntent);
}
};
In the second page use getExtras("PASSVALUE") to retrieve data that you passed
See this post for more details
http://mylifewithandroid.blogspot.com/2007/12/playing-with-intents.html
Answer-1)
For that you need to pass the value in intent and that value you get in another activity.
Intent i = new Intent(YourCurrentActivity.this,YourCallingActivity.this);
i.putExtra("key", YourValueToPassAnotherActivity);
startActivity(i);
Now you can get this value in your calling activity using bundle.
Bundle b = getIntent().getExtras();
b.getString("key");
Answer-2)
For that you need to create custom title bar.
This might help you
http://oo-androidnews.blogspot.com/2010/03/android-how-to-add-custom-title-bar.html