(Android) Basics & snippets

1.Basics.java

// Set the user interface layout for this Activity (activity_main.xml)
//Usually in the onCreate method
setContentView(R.layout.activity_main);

//R.java file have all the resources IDs provided to resources(drawables, layouts, styles etc)
//Example
R.id.edit_message //id of a layout view in the xml



//Progress dialog
progressDialog = ProgressDialog.show(this, null, getString(R.string.waiting));



/*Intents***********************************************************/
//1st parameter is the context (Activity is a subclass of Context)
//2d parameter is the class to which the system should deliver the intent
Intent intent = new Intent(this, DisplayMessageActivity.class);
    	
//findViewById returns the View found with the specific id
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
    	
//An Intent can carry a collection of various data types as key-value pairs called extras.
//The putExtra() method takes the key name in the first parameter and the value in the second parameter.
intent.putExtra(EXTRA_MESSAGE, message);
//Needs definition
    //Key for the intent extra (see above)
    //Example
    public final static String EXTRA_MESSAGE = "gr.atc.learningapp.MESSAGE";
    	
//Start the other activity with the specific intent
//f the system identifies more than one activity that can handle the intent
//it displays a dialog for the user to select which app to use
startActivity(intent);

//OR
//With animation
ActivityOptions options = ActivityOptions.makeScaleUpAnimation(view, 0, 0, view.getWidth(), view.getHeight());
startActivity(intent, options.toBundle());



/*******************************************/
//OR
//If you want to start an activity and get a result back
//(Ex. your app can start a camera app and receive the captured photo as a result)
//EXAMPLE
Intent intent;

//Weather you will take a new photo or pick one from the photo library
switch (itemPosition) {
	case 0:	
		File f;			
		try {
			f = createImageFile();
			intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
			intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));
			startActivityForResult(intent,Utils.RC_PICK_FROM_CAMERA);
			//(intent, requestCode) if requestCode>=0 this will be returned in
                        //onActivityResult on the receiver class which will take the ewquestCode also to know where
                        //the result is coming from
		}
        catch (Exception e) {
			e.printStackTrace();
		}

		dialog.cancel();
		break;
	case 1:
	    intent = new Intent();
		intent.setType("image/*");
		intent.setAction(Intent.ACTION_GET_CONTENT);
		startActivityForResult(Intent.createChooser(intent,getString(R.string.options)),Utils.RC_PICK_FROM_FILE);

		break;
}

//In general
//start an activity and expect a result
Intent i = new Intent(this, SecondActivity.class);
startActivityForResult(i, 1);	//2d parameter is a flag that if >=0 result will go to onActivityResult

//The activity that responds must be designed to return a result !
//LIKE SO:
    Intent resultIntent = new Intent();
    // TODO Add extras or a data URI to this intent as appropriate.
    intent.putExtra(SOME_KEY, somevalue);
    setResult(Activity.RESULT_OK, resultIntent);
    finish();

/************************************************************/
//or an activity where you can select a Contact:
private void pickContact() {
    Intent pickContactIntent = new Intent(Intent.ACTION_PICK, Uri.parse("content://contacts"));
    pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers
    startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST);
    //static final int PICK_CONTACT_REQUEST = 1;  // The request code
}

//When the user is done with the subsequent activity and returns,
//the system calls your activity's onActivityResult() method
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // Check which request we're responding to
    if (requestCode == PICK_CONTACT_REQUEST) {
        // Make sure the request was successful
        //If user cancelled it will show RESULT_CANCELED
        if (resultCode == RESULT_OK) {
            // Get the URI that points to the selected contact
            Uri contactUri = data.getData();
            // We only need the NUMBER column, because there will be only one row in the result
            String[] projection = {Phone.NUMBER};

            // Perform the query on the contact to get the NUMBER column
            // We don't need a selection or sort order (there's only one result for the given URI)
            // CAUTION: The query() method should be called from a separate thread to avoid blocking
            // your app's UI thread. (For simplicity of the sample, this code doesn't do that.)
            // Consider using CursorLoader to perform the query.
            Cursor cursor = getContentResolver().query(contactUri, projection, null, null, null);
            cursor.moveToFirst();

            // Retrieve the phone number from the NUMBER column
            int column = cursor.getColumnIndex(Phone.NUMBER);
            String number = cursor.getString(column);

            // Do something with the phone number...
        }
    }
}

/*******************************************/


//To verify there is an activity available that can respond to the intent, call queryIntentActivities()
//to get a list of activities capable of handling your Intent.
//If the returned List is not empty, you can safely use the intent.
PackageManager packageManager = getPackageManager();
List<ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0);
boolean isIntentSafe = activities.size() > 0;


// Start an activity if it's safe
if (isIntentSafe) {
    startActivity(mapIntent);
}


//Show an App Chooser for the Intent
Intent intent = new Intent(Intent.ACTION_SEND);
...
// Always use string resources for UI text. This says something like "Share this photo with"
String title = getResources().getText(R.string.chooser_title);
// Create and start the chooser
Intent chooser = Intent.createChooser(intent, title);
startActivity(chooser);
//This displays a dialog with a list of apps that respond to the intent passed to the createChooser() method
//and uses the supplied text as the dialog title.


//If you're done with the activity
// remove the activity from the back stack
LoginActivity.this.finish();




//Get a message from an Intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
/******************************************************************/


//Check running version of Android
// Make sure we're running on Honeycomb or higher to use ActionBar APIs
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
  // Show the Up button in the action bar.
  ActionBar actionBar = getActionBar();
  actionBar.setDisplayHomeAsUpEnabled(true);
            
  // Make sure the app icon in the action bar does not behave as a button
  actionBar.setHomeButtonEnabled(false);
}


//Implicit intents do not declare the class name of the component to start, but instead declare an action to perform
//Call a number
Uri number = Uri.parse("tel:5551234");
Intent callIntent = new Intent(Intent.ACTION_DIAL, number);




//Check internet connectivity
ConnectionDetector cd = new ConnectionDetector(getApplicationContext());
Boolean isInternetPresent = cd.isConnectingToInternet(); // true or false

//Add internet Permission in Manifest file
<uses-permission android:name="android.permission.INTERNET"></uses-permission>




//View a map
// Map point based on address
Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
// Or map point based on latitude/longitude
Uri location = Uri.parse("geo:37.422219,-122.08364?z=14"); // z param is zoom level
Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);


//View a Web page
Uri webpage = Uri.parse("http://www.android.com");
Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage);


//Send email with attachment
Intent emailIntent = new Intent(Intent.ACTION_SEND);
// The intent does not have a URI, so declare the "text/plain" MIME type
emailIntent.setType(HTTP.PLAIN_TEXT_TYPE);
emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[] {"jon@example.com"}); // recipients
emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Email subject");
emailIntent.putExtra(Intent.EXTRA_TEXT, "Email message text");
emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("content://path/to/email/attachment"));
// You can also attach multiple items by passing an ArrayList of Uris


//Add a calendar event
Intent calendarIntent = new Intent(Intent.ACTION_INSERT, Events.CONTENT_URI);
Calendar beginTime = Calendar.getInstance().set(2012, 0, 19, 7, 30);
Calendar endTime = Calendar.getInstance().set(2012, 0, 19, 10, 30);
calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
calendarIntent.putExtra(Events.TITLE, "Ninja class");
calendarIntent.putExtra(Events.EVENT_LOCATION, "Secret dojo");

//WEBVIEW
//Load the web view
webView = (WebView) findViewById(R.id.webView);
webView.setWebViewClient(new WebViewClient());
webView.getSettings().setJavaScriptEnabled(true);
webView.loadUrl(url);  
		
		
//Hide (dim) the navigation buttons
getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION); 

2.easyShareAction.java

/*
Implementing an effective and user friendly share action in your ActionBar

//You need to define android:actionProviderClass attribute for the corresponding <item> in your menu resource file:

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/menu_item_share"
        android:showAsAction="ifRoom"
        android:title="Share"
        android:actionProviderClass="android.widget.ShareActionProvider" />
    ...
</menu>
*/

private ShareActionProvider mShareActionProvider;
...

@Override
public boolean onCreateOptionsMenu(Menu menu) {
  
    // Inflate menu resource file.
    getMenuInflater().inflate(R.menu.share_menu, menu);

    // Locate MenuItem with ShareActionProvider
    MenuItem item = menu.findItem(R.id.menu_item_share);

    // Fetch and store ShareActionProvider
    mShareActionProvider = (ShareActionProvider) item.getActionProvider();

    // Return true to display menu
    return true;
}

// Call to update the share intent
private void setShareIntent(Intent shareIntent) {
  
    if (mShareActionProvider != null) {
        mShareActionProvider.setShareIntent(shareIntent);
    }
}

3.alertDialogs.java

AlertDialog alertDialog = new AlertDialog.Builder(
                        AlertDialogActivity.this).create();
 
        // Setting Dialog Title
        alertDialog.setTitle("Alert Dialog");
 
        // Setting Dialog Message
        alertDialog.setMessage("Welcome to AndroidHive.info");
 
        // Setting Icon to Dialog
        alertDialog.setIcon(R.drawable.tick);
 
        // Setting OK Button
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                // Write your code here to execute after dialog closed
                Toast.makeText(getApplicationContext(), "You clicked on OK", Toast.LENGTH_SHORT).show();
                }
        });
        
        //OR 2 BUTTONS
        
        // Setting Positive "Yes" Button
        alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
 
            // Write your code here to invoke YES event
            Toast.makeText(getApplicationContext(), "You clicked on YES", Toast.LENGTH_SHORT).show();
            }
        });
 
        // Setting Negative "NO" Button
        alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            // Write your code here to invoke NO event
            Toast.makeText(getApplicationContext(), "You clicked on NO", Toast.LENGTH_SHORT).show();
            dialog.cancel();
            }
        });
        
        //OR ADD A 3D ONE
        
        // Setting Netural "Cancel" Button
        alertDialog.setNeutralButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            // User pressed Cancel button. Write Logic Here
            Toast.makeText(getApplicationContext(), "You clicked on Cancel",
                                Toast.LENGTH_SHORT).show();
            }
        });
 
        // Showing Alert Message
        alertDialog.show();

4.eventListeners.java

/* http://developer.android.com/guide/topics/ui/ui-events.html

An event listener is an interface in the View class that contains a single callback method.
These methods will be called by the Android framework when the View to which the listener has been registered
is triggered by user interaction with the item in the UI.

public void onClick()
public boolean onLongClick()
onFocusChange()
public boolean onKey()             When focused and pressed a key
onKeyDown()
onKeyUp()
public boolean onTouch()
onCreateContextMenu()
more..
*/

//You can put it the onClick in the xml layout or you can do it by code:

// Create an anonymous implementation of OnClickListener
private OnClickListener mCorkyListener = new OnClickListener() {
    public void onClick(View v) {
      // do something when the button is clicked
    }
};

protected void onCreate(Bundle savedValues) {
    ...
    // Capture our button from layout
    Button button = (Button)findViewById(R.id.corky);
    // Register the onClick listener with the implementation above
    button.setOnClickListener(mCorkyListener);
    ...
}

//OR IMPLEMENT IT IN YOUR CLASS

public class ExampleActivity extends Activity implements OnClickListener {
    protected void onCreate(Bundle savedValues) {
        ...
        Button button = (Button)findViewById(R.id.corky);
        button.setOnClickListener(this);
    }

    // Implement the OnClickListener callback
    public void onClick(View v) {
      // do something when the button is clicked
    }
}

//OR
//All the way
button.setOnClickListener(new OnClickListener() {

    	@Override
	public void onClick(View v) {
		Intent login = new Intent(DashboardActivity.this,LoginActivity.class);
		
		startActivity(login);

		// remove the activity from the back stack
		DashboardActivity.this.finish();
		overridePendingTransition(android.R.anim.fade_in,android.R.anim.fade_out);
	}
});

5.FastMultipleChoiceAleftdialog.java

final CharSequence[] items = {"Red", "Green", "Blue", "Purple"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);

builder.setTitle("Pick color(s)")
        .setMultiChoiceItems(items, null, new DialogInterface.OnMultiChoiceClickListener() {
          
            @Override
            public void onClick(DialogInterface dialog, int which,
                    boolean isChecked) {
                Log.d(tag, items[which] + " " + isChecked);
            }
        })
        .setPositiveButton("OK", new DialogInterface.OnClickListener() {
          
            @Override
            public void onClick(DialogInterface dialog, int which) {
              
                //reading content of the dialog
                AlertDialog a = ((AlertDialog)dialog);
                Log.d(tag, "" + a.getListView().getCheckedItemCount());
                
                for(long i: a.getListView().getCheckItemIds())
                {
                    Log.d(tag, i + "");
                }
            }
        });
 
        final AlertDialog alert = builder.create();
        
        ((Button) findViewById(R.id.button4)).setOnClickListener(new View.OnClickListener() {
          
                    @Override
                    public void onClick(View v) {
                        alert.show();
                    }
                });