android app
Post on 21-Dec-2015
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• Activities – visual user interface focused on a
single thing a user can do
• Services – no visual interface – they run in the
background
• Broadcast Receivers – receive and react to
broadcast announcements
• Content Providers – allow data exchange
between applications
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Java code for our activity All source code here
Generated Java code
Helps link resources to
Java code
Layout of the activity
Strings used in the
program
All non-code
resources
Android Manifest
Images
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• src – your source code
• gen – auto-generated code (usually just R.java)
• Included libraries
• Resources
– Drawables (like .png images)
– Layouts
– Values (like strings)
• Manifest file
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• Used to define some of the resources
– Layouts (UI)
– Strings
• Manifest file
• Shouldn’t usuall have to edit it directl , Eclipse can do that for you
• Preferred way of creating UIs
– Separates the description of the layout from any actual code that controls it
– Can easily take a UI from one platform to another
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• Auto-generated: ou shouldn’t edit it • Contains IDs of the project resources
• Enforces good software engineering
• Use findViewById and Resources object to get
access to the resources
– Ex. Button b = (Button)findViewById(R.id.button1)
– Ex. getResources().getString(R.string.hello));
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• A TextView displays text to the user and optionally allows them to edit it. A TextView is a complete text editor, however the basic class is configured to not allow editing
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• text: defines the text that would be displayed on the screen.
• textStyle: sets the style of the text.
• textSize: defines the size of the text.
• textColor: sets the color of the text.
• background: sets the background color.
• autoLink: identifies the links into the text and converts them into clickable ones. The available choices are web, email, phone.
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• android:text="@stri g/* a e“ • android:textSize="30sp“ • android:textAppearance="?android:attr/t
extAppearanceLarge“ • android:id="@+id/te t2“
• android:fontFamily="Arial“ • android:textStyle="bold“ • android:textColor="#aarrggbb“
• android:background="#aarrggbb"
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SP/DP
• px is one pixel.
• sp is scale-independent pixels.
• dp is Density-independent pixels.
• sp for font sizes
• dp for everything else.
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You have to create the Color.xml file in the res/value folder of your project. The
code of Color.xml is
<?xml version="1.0" encoding="utf-8"?>
<color name="white">#FFFFFF</color>
<color name="yellow">#FFFF00</color>
<color name="fuchsia">#FF00FF</color>
<color name="red">#FF0000</color>
<color name="silver">#C0C0C0</color>
<color name="gray">#808080</color>
<color name="olive">#808000</color>
<color name="purple">#800080</color>
<color name="maroon">#800000</color>
<color name="aqua">#00FFFF</color>
<color name="lime">#00FF00</color>
<color name="teal">#008080</color>
<color name="green">#008000</color>
<color name="blue">#0000FF</color>
<color name="navy">#000080</color>
<color name="black">#000000</color>
android:textColor="@color/red"
BACKGROUND COLOR:
android:background="#aabbcc“
BACKGROUND IMAGE:
SAVE IMAGE(.PNG) INTO DRAWABLE FOLODER
android:background="@drawable/images"
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• android:layout_marginBottom= ..dp
• android:layout_marginLeft= ..dp
• android:layout_gravity= ..center
• android:gravity= ..center
• android:layout_marginTop="dp“ • android:layout_width=“dp"
• android:layout_height="dp"
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• findViewById();
• onClick(View v);
• Gettext();
• Settext();
• OnClickListener();
• setOnClickListener();
• Toast.makeText
• Toast.LENGTH_LONG
• show()
• getApplicationContext(),
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Change button name/size/color:
android:text="@stri g/a“ android:textSize="30sp"
android:textColor="#aabbcc“ android:textStyle="bold“ android:background=“#aabbcc“ android:layout_width="100dp"
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• In Android, Toast is a notification message that
pop up, display a certain amount of time, and
automatically fades in and out.
DISPLAY THE MESSAGE: //display in short period of time
Toast.makeText(getApplicationContext(), "msg msg",
Toast.LENGTH_SHORT).show();
//display in long period of time
Toast.makeText(getApplicationContext(), "msg msg",
Toast.LENGTH_LONG).show();
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BUTTON EVENT
Button bt.
bt=(Button)findViewById(R.id.button1);
bt.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(),
"hi dear", Toast.LENGTH_LONG).show();
}
});
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Button bt;
TextView t;
bt=(Button)findViewById(R.id.button1);
t=(TextView)findViewById(R.id.textView1);
bt.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
t.setText “ our string" ;
}
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ImageView i;
i=(ImageView)findViewById(R.id.imageView1);
For showing the Image
i.setImageResource(R.drawable.ic_launcher);
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Retrieving data from an EditText
getText()
EXAMPLE:
EditText etName = (EditText) findViewById(R.id.editText1);
strName = etName.getText().toString();.
android:layout_weight="1"
android:maxLength="5"
android:inputType="number"
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b=(Button)findViewById(R.id.button1);
t=(EditText)findViewById(R.id.editText1);
b.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
String mystr=t.getText().toString(); Toast msg=Toast.makeText(getBaseContext(),mystr,Toast.LENGTH_LONG);
msg.show();
}
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Stringbuffer
String mystr=t.getText().toString();
String result = new
StringBuffer(mystr).reverse().toString();
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FOR PLUS:
public void onClick(View arg0) {
try{
int x=Integer.parseInt(a.getText().toString());
int y=Integer.parseInt(b.getText().toString());
int sum=x+y;
shw.setText(""+sum);
// TODO Auto-generated method stub
}
catch(Exception e)
{
}
}
});
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Toggle Button on and off
Android ToggleButton is two state button same as RadioButton and
CheckBox. And these two states are on and Off . When ToggleButton
is on then it shows a green bar and when it is in off state it shows a grey
bar. this is default behavior.
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• android:layout_width="match_parent
• android:layout_height="wrap_content
• android:text="ToggleButton
• android:textOff="Toggele button off
• android:textOn="Toggle button is on
• setChecked(true)
• setChecked(false)
• isChecked()
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Toggle Button( XML)
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<ToggleButton
android:id="@+id/toggleButton1"
android:layout_width="127dp"
android:layout_height="wrap_content"
android:textOn="yes"
android:textOff="no"
android:checked="false"/>
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ToggleButton t;
Button b;
TextView et;
t=(ToggleButton) findViewById(R.id.toggleButton1);
b=(Button) findViewById(R.id.button1);
et=(TextView) findViewById(R.id.textView1);
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b.setOnClickListener( new OnClickListener() {
public void onClick(View arg0) {
if(t.isChecked())
{
et.setText("toggle button is pressed");
t.setChecked(true);
}
else
{
et.setText("toggle button is off");
t.setChecked(false);
}
}
});
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You often use radio buttons when a user
should be allowed to only select one item
from a small group of items.
android:checked= true
android:checked="false"
getCheckedRadioButtonId();
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1.Link with XML RadioGroup rg;
Button b;
rg=(RadioGroup)findViewById(R.id.radioGroup1);
b=(Button)findViewById(R.id.button1);
2.Attached Click listener to Button
b.setOnClickListener(this);
3. Implements OnClickListener
public class Radio1Activity extends Activity implements OnClickListener{
**ADD UNIMPLEMENTED METHOD
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public void onClick(View v) {
if( v==b)
{
RadioButton selectRadio = (RadioButton)
findViewById(rg.getCheckedRadioButtonId());
String opinion = selectRadio.getText().toString();
Toast.makeText(this, "Your Opinion is : " +
opinion,Toast.LENGTH_LONG).show();
}
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• One of the easiest and most common ways to
accept user input in an Android Application is
the Checkbox component.
• Implement view.onclickListener
• isChecked Method
Determine if the box is checked using
isChecked() method
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• android:checked="false
• android:text="@string/b"
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c.setOnClickListener(this);
public class CheboxActivity extends Activity {
/** Called when the activity is first created. */
CheckBox c;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
c=(CheckBox) findViewById(R.id.checkBox1);
c.setOnClickListener(this);
}
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• Implement the OnClickListener interface for
the activity class .
• Call the setOnClickListener() object by passing
the context as a paramter to it .
• Override the onClick(View v) method inside
the activity class .
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public class CheboxActivity extends Activity
implements OnClickListener {
/** Called when the activity is first created. */
CheckBox c;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
c=(CheckBox) findViewById(R.id.checkBox1);
c.setOnClickListener(this);
}
}
**ADD UNIMPLEMENTED METHOD
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public void onClick(View v) {
// TODO Auto-generated method stub
}
This is a method which is get called whether
Checkbox Is checked or not.
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(View v) is checkbox object
public void onClick(View v) {
CheckBox t=(CheckBox) v;
if(t.isChecked())
{
Toast.makeText(getApplicationContext , your msg" , Toast.LENGTH_LONG).show();
}
else
{
Toast.makeText(getApplicationContext , your msg" , Toast.LENGTH_LONG).show();
}
}
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public void onClick(View v)
{
switch(v.getId())
{
case R.id.checkbox1:
break;
case R.id.cbox2:
break;
............and so on }
}
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if (checkBox1.isChecked())
{
checkBox1.setChecked(false);
} if (checkBox2.isChecked())
{
checkBox2.setChecked(false);
}
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public void onClick(View v) {
switch(v.getId())
{
case R.id.checkBox1:
c2.setChecked(false);
c3.setChecked(false);
c4.setChecked(false);
Toast.makeText(this, "yes", Toast.LENGTH_LONG).show();
break;
So on.....................
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//String edit="";
Button btn;
EditText ed;
ToggleButton toggle;
btn = (Button)findViewById(R.id.button1);
ed = (EditText)findViewById(R.id.editText1);
toggle =
(ToggleButton)findViewById(R.id.toggleButton1);
//edits = ed.getText().toString();
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Toggle Button(eg)
btn.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
edit = ed.getText().toString();
if(edit.equals("1")){
toggle.setTextOff("TOGGLE ON");
toggle.setChecked(true);
}
else if(edit.equals("0")){
toggle.setTextOn("TOGGLE OFF");
toggle.setChecked(false);
}
}
});
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Starting activities
startActivity()
Example:
Intent i = new Intent(ac1,ac2); startActivity(i);
Intent.ACTION_VIEW
Uri.parse
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Intent can be used to perform following 3 tasks
• Open another Activity or Service from the
current Activity
• Pass data between Activities and Services
• Delegate responsibility to another application.
For example, you can use Intents to open the
browser application to display a URL.
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• When you know which component you want
to launch .
• When you open an activity from another
activity in the same Android app, you use
Explicit Intents.
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you do not know which component should be
launched. Or if you want to give the user an
option to choose between a list of
components to use.
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Button go,fa,gm;
addListenerOnButton();//method
}
public void addListenerOnButton() {
gm=(Button)findViewById(R.id.button1);
go=(Button)findViewById(R.id.button2);
fa=(Button)findViewById(R.id.button3);
gm.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) { Intent bw=new Intent(Intent.ACTION_VIEW,Uri.parse("http://www.gmai.com"));
startActivity(bw);// TODO Auto-generated method stub
}
});
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1.TWO ACTIVITY FILE
FirstActivit
secondActivity
2.TWO XML FILE
MAIN.XML
SECOND.XML
setContentView(R.layout.second);//CHANGE LAYOUT
3.Entry new activity into androidmainfest.xml
<activity android:name="secondActivity">
</activity>
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Button btn;
btn=(Button)findViewById(R.id.button1);
btn.setOnClickListener(new OnClickListener() {
public void onClick(View v) { Intent i=new Intent(firstActivity.this,secondActivity.class);
startActivity(i);
}
});
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Button b;
b=(Button)findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
finish();
}
});
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