i' m new on android, i want to know what are the differences to declare a button like :
#Override
protected void onCreate(Bundle savedInstanceState) {
button = ((Button) findViewById(R.id.button));
button.setOnClickListener(this);
}
or
#Override
protected void onCreate(Bundle savedInstanceState) {
button = new Button(this);
button.setId(..);
button = ((Button) findViewById(R.id.button));
button.setOnClickListener(this);
}
thanks in advance.
If you declare the Button in xml then you should provide a layout to the Activity using setContentView(int) and initialize the Button like this
#Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.your_layout);//a button with id button should present in this layout
button = (Button) findViewById(R.id.button);
button.setOnClickListener(this);
}
If you want to create a Button programmatically then you should do initialization like this
#Override
protected void onCreate(Bundle savedInstanceState) {
button = new Button(this);
button.setId(1);//some random integer value
setContentView(view);//some view
button.setOnClickListener(this);
}
setContentView(View view) for 2nd case
If you use first declaration, you have to define a button from xml. In the second one you are creating a button programmatically. You can also define it's position in the view etc.
The difference is that the second time you declare the button in the code. Then you add an id to it, presumably a new one.
If you want to run the first code your button has to be declared in the xml layout resource file. This is the fastest way since it is optimized on the android framework to read the layouts from xml (it is actually converted to java, but in an optimized way).
The second code does not require the layout file, although you do not add the button to a layout so the button as it is now is not usable, as it is not 'on screen'.
The difference is that
xml based layout is comparatively fast
xml based code at the end it converted in to java code by the compiler
and if you will use the second approach you have to do allot of things like setting the
width and height, position where it to be shown and by doing that
Your code will be messy
So it its better to use xml based layouts
Related
I'm new to android development. I've a doubt.
I know that you can add a button and initialize it like
Button b1=(Button) findViewById(R.id.button1);
and I can also give a unction name in the XML file.
android:onClick="click_event"
My doubt is, which is the best and efficient way?
like it says that its better to use #string resource instead of a hard-coded one.
I think you are confused. The examples you give are two different things.
Adding a Button
This line
Button b1=(Button) findViewById(R.id.button1);
doesn't add a Button. It declares and initializes an instance of Button which refers to a Button in your currently inflated xml which has an id of button1
So in your xml you would have somewhere
<Button
android:id="#+id/button1"
<!-- other properties -->
/>
You can add a Button programmatically with
Button bt1 = new Button(this);
// give it properties
But it is generally easier to do in xml because here you have to programmatically give it parameters, properties, and add it to an inflated layout
OnClick
As far as the onClick() it depends on what you feel is the easiest and best in your situation. I like to declare it in the xml like that often but you can do it several ways. Using this method you just have to be sure that you have a function like this that is public and takes only one parameter and that parameter must be a View
public void clickEvent(View v)
{
// code here
}
I also changed the name so your xml would be like
<Button
android:id="#+id/button1"
<!-- other properties -->
android:onClick="clickEvent"/>
You also can set onClick() in your Java with something like
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
// code here
}
});
or
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(this);
#Override
public void onClick(View v)
{
// code here
}
Note that the last way you will need to add implements OnClickListener in your Activity declaration
public class MyActivity extends Activity implements OnClickListener
{
You can also create your own click Listener by changing it to something like
b1.setOnClickListener(myBtnClick);
then create an instance of it with something like
public OnClickListener myBtnClick = new OnClickListener()
{
#Override
public void onClick(View v)
{
// click code here
}
};
You can use this for multiple Buttons and switch on the id or check the View param to know which Button was clicked or create separate Listeners for different Buttons.
I'm new to android development. I've a doubt.
I know that you can add a button and initialize it like
Button b1=(Button) findViewById(R.id.button1);
and I can also give a unction name in the XML file.
android:onClick="click_event"
My doubt is, which is the best and efficient way?
like it says that its better to use #string resource instead of a hard-coded one.
I think you are confused. The examples you give are two different things.
Adding a Button
This line
Button b1=(Button) findViewById(R.id.button1);
doesn't add a Button. It declares and initializes an instance of Button which refers to a Button in your currently inflated xml which has an id of button1
So in your xml you would have somewhere
<Button
android:id="#+id/button1"
<!-- other properties -->
/>
You can add a Button programmatically with
Button bt1 = new Button(this);
// give it properties
But it is generally easier to do in xml because here you have to programmatically give it parameters, properties, and add it to an inflated layout
OnClick
As far as the onClick() it depends on what you feel is the easiest and best in your situation. I like to declare it in the xml like that often but you can do it several ways. Using this method you just have to be sure that you have a function like this that is public and takes only one parameter and that parameter must be a View
public void clickEvent(View v)
{
// code here
}
I also changed the name so your xml would be like
<Button
android:id="#+id/button1"
<!-- other properties -->
android:onClick="clickEvent"/>
You also can set onClick() in your Java with something like
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
// code here
}
});
or
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(this);
#Override
public void onClick(View v)
{
// code here
}
Note that the last way you will need to add implements OnClickListener in your Activity declaration
public class MyActivity extends Activity implements OnClickListener
{
You can also create your own click Listener by changing it to something like
b1.setOnClickListener(myBtnClick);
then create an instance of it with something like
public OnClickListener myBtnClick = new OnClickListener()
{
#Override
public void onClick(View v)
{
// click code here
}
};
You can use this for multiple Buttons and switch on the id or check the View param to know which Button was clicked or create separate Listeners for different Buttons.
I'm new to android development. I've a doubt.
I know that you can add a button and initialize it like
Button b1=(Button) findViewById(R.id.button1);
and I can also give a unction name in the XML file.
android:onClick="click_event"
My doubt is, which is the best and efficient way?
like it says that its better to use #string resource instead of a hard-coded one.
I think you are confused. The examples you give are two different things.
Adding a Button
This line
Button b1=(Button) findViewById(R.id.button1);
doesn't add a Button. It declares and initializes an instance of Button which refers to a Button in your currently inflated xml which has an id of button1
So in your xml you would have somewhere
<Button
android:id="#+id/button1"
<!-- other properties -->
/>
You can add a Button programmatically with
Button bt1 = new Button(this);
// give it properties
But it is generally easier to do in xml because here you have to programmatically give it parameters, properties, and add it to an inflated layout
OnClick
As far as the onClick() it depends on what you feel is the easiest and best in your situation. I like to declare it in the xml like that often but you can do it several ways. Using this method you just have to be sure that you have a function like this that is public and takes only one parameter and that parameter must be a View
public void clickEvent(View v)
{
// code here
}
I also changed the name so your xml would be like
<Button
android:id="#+id/button1"
<!-- other properties -->
android:onClick="clickEvent"/>
You also can set onClick() in your Java with something like
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
// code here
}
});
or
Button b1=(Button) findViewById(R.id.button1);
b1.setOnClickListener(this);
#Override
public void onClick(View v)
{
// code here
}
Note that the last way you will need to add implements OnClickListener in your Activity declaration
public class MyActivity extends Activity implements OnClickListener
{
You can also create your own click Listener by changing it to something like
b1.setOnClickListener(myBtnClick);
then create an instance of it with something like
public OnClickListener myBtnClick = new OnClickListener()
{
#Override
public void onClick(View v)
{
// click code here
}
};
You can use this for multiple Buttons and switch on the id or check the View param to know which Button was clicked or create separate Listeners for different Buttons.
Let's pretend this was my Java Class...
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button ScreentwoGameButton = (Button) findViewById(R.id.screentwo);
ScreentwoGameButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent ScreentwoGameIntent = new Intent(Main.this, Screentwo.class);
startActivity(StartGameIntent);
}
});
How do i use this code below but the right way like.
So let's put an example if I click screentwo button the screentwo.xml will show and it will allow me to click inside if any buttons are available. Instead just stare what's in the layout.
I don't want to use the Activity to activity cause the whole point is i'm trying to avoid the flashing looking feel going to another java class.
If you look at the moron test game on Android it says example: press the blue button then red and then green, so if u press the blue button the screen will remain and not flash at all but the image of the blue button will disappear and I'm allowed to click the red and then green.
Hope that helped.
Thanks
Wahid
Button ScreentwoButton = (Button) findViewById(R.id.screentwo);
ScreentwoButton.setOnClickListener(new OnClickListener() {
private Uri Uri;
#Override
public void onClick(View v) {
setContentView(R.layout.Screentwo);
Uri uri=Uri;
Intent i=new Intent(Intent.ACTION_VIEW, uri);
mSoundManager.playSound(1);
}
});
try to use:
setContentView(R.layout.next layout); in your button click.
You could use the viewflipper class and add the different layouts as childs to the viewflipper
and set the active child. Using setcontentView will be trouble some when you use findViewById for a old layout. As findViewById will look in the layout that is specified by setContentView
I have a LinearLayout comprising of a few Buttons and I add this to my activity in the onCreate(..) method with setContentView(R.layout.myscreen). No surprises so far.
How do I get a reference to an iterator to these buttons? I'd like to add listeners to them but I'd rather not directly reference the Button's using their android:id.
Similar questions have been asked here and here but they don't quite answer my question.
Try something like this provide an id root_layout in xml to LinearLayout
LinearLayout mLayout = (LinearLayout) findViewById(R.id.root_layout);
for(int i = 0; i < mLayout.getChildCount(); i++)
{
Button mButton = (Button) mLayout.getChildAt(i);
mButton.setOnClickListener(this);
}
Where mLayout is object of you Linear Layout and Your activity must implements OnClickListener and here goes general listener
#Override
public void onClick(View v)
{
Button mButton = (Button)v;
String buttonText = mButton.getText().toString();
}
NOTE: For this to work properly you Linear Layout must only contains button no other views
You should take a look at my answer here.
In short. I'd assign the buttons a listener by setting the onClick attribute in the XML layout on each Button.
Inside of your Activity you'll need a public method like the one below which basically is what you want to do in your listener.
public void myFancyMethod(View v) {
// do something interesting here
}
If you want to go for accessing other elements you may try following syntax:
<ElementClass> <referencevariable> = (<ElementClass>) findViewById(R.id.<id_of_the_element>);
For Example:
TextView textView= (TextView) findViewById(R.id.t1); //I used t1 to refer my textview in the Layout.
This might work.
Then you can use these views with their inbuilt methods to perform as many as work you want.