What is intent ?

It is a kind of message or information that is passed to the components. It is used to launch an activity, display a web page, send sms, send email etc. There are two types of intents in android:

1. Implicit Intent
2. Explicit Intent

 

What are the life cycle methods of android Activity ?

  As an activity transitions from state to state, it is notified of the change by calls to the  

  following protected methods:

1.     void onCreate(Bundle savedInstanceState)
2.     void onStart()
3.     void onRestart()
4.     void onResume()
5.     void onPause()
6.     void onStop()
7.     void onDestroy()

 

 Taken together, these seven methods define the entire lifecycle of an activity.

 

What is activity ?

Activity is like a frame or window in java that represents GUI. It represents one screen of android.

An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map. Each activity is given a window in which to draw its user interface. The window typically fills the screen, but may be smaller than the screen and float on top of other windows.

 

What are the core building blocks of android ?

The core building blocks of android are:

• Activity - single screen on android mobile
• View
• Fragment 
• Services – like Network Operation 
•  Intent - To perform inter-communication between activities or services.
•  Resource Externalization - such as strings and graphics.
•  Notification signaling users - light, sound, icon, notification, dialog etc.
•  Content Providers - They share data between applications
•  How will you record a phone call in Android? How to get a handle on Audio Stream for a call in Android?
•  Permissions.PROCESS_OUTGOING_CALLS: Allows an application to monitor, modify, or abort outgoing calls.

 

What are the advantages of android ?

Open-source: It means no licence, distribution and development fee.

Platform-independent: It supports windows, mac and linux platforms.

Supports various technologies: It supports camera, bluetooth, wifi, speech, EDGE etc. technologies.

Highly optimized Virtual Machine: Android uses highly optimized virtual machine for mobile devices, called DVM (Dalvik Virtual Machine).

 It is simple and powerful SDK.
 Licensing, Distribution or Development fee is not required.
 Easy to Import third party Java library.
 Supporting platforms are – Linux, Mac Os, Windows.
 Innovative products like the location-aware services, location of a nearby convenience store  etc., are some of  the additive facilities in Android. Components can be reused and replaced by  the application framework. 
 Optimized DVM for mobile devices.
 SQLite enables to store the data in a structured manner.
 Supports GSM telephone and Bluetooth, WiFi, 3G and EDGE technologies.
 The development is a combination of a device emulator, debugging tools, memory profiling and  plug-in for  Eclipse IDE.
 The customer will be benefited from wide range of mobile applications to choose.

 

What is Android 

Android is a stack of software for mobile devices which includes an Operating System, middleware and some key applications. The application executes within its own process and its own instance of Dalvik Virtual Machine. Many Virtual Machines run efficiently by a DVM device. DVM executes Java languages byte code which later transforms into .dex format files.

ANDROID MULTIPAL RUNTIME PERMISSION:

Think of a scenario where you might need to ask for multiple permissions. For this, instead of requesting multiple permissions in multiple dialogs, we can prompt all the permissions in a single dialog where permissions will be scrolled through one after another.

eg:
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

Step 1: We checked for multiple permission with checkSelfPermission() similar as Single permission.

if(ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[0]) != PackageManager.PERMISSION_GRANTED

                        || ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[1]) != PackageManager.PERMISSION_GRANTED

                        || ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[2]) != PackageManager.PERMISSION_GRANTED){

..............

}

else{

.............

}

Step 2: We used shouldShowRequestPermissionRationale() method to check if we should show the explanation for the permission or not similar as single permission.

if(ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[0])

                            || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[1])

                            || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[2])){

}

Now, how we achieve this is by creating string array with required permissions. While checking for permissions, checked by all elements of the array. The only exception is in while checking with SharedPreferences, here we’ve checked with only the first string, the reason is that for storing shared preferences on string is enough and only one shared preference can tell us whether we’ve already requested for permissions or not (as we are requesting for all permissions in one go).

In the onRequestPermissionsResult() method we used a for loop to determine whether all permissions are granted or not. If a single permission is not granted then we will not proceed further.

Just like: 

 @Override

    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if(requestCode == PERMISSION_CALLBACK_CONSTANT){

            //check if all permissions are granted

            boolean allgranted = false;

            for(int i=0;i<grantResults.length;i++){

                if(grantResults[i]==PackageManager.PERMISSION_GRANTED){

                    allgranted = true;

                } else {

                    allgranted = false;

                    break;

                }

            }

            if(allgranted){

                proceedAfterPermission();

            }

FINAL CODE:
public class MultiplePermissionsActivity extends AppCompatActivity {

    private static final int PERMISSION_CALLBACK_CONSTANT = 100;
    private static final int REQUEST_PERMISSION_SETTING = 101;
    String[] permissionsRequired = new String[]{Manifest.permission.CAMERA,
            Manifest.permission.ACCESS_FINE_LOCATION,
            Manifest.permission.ACCESS_COARSE_LOCATION};
    private TextView txtPermissions;
    private Button btnCheckPermissions;
    private SharedPreferences permissionStatus;
    private boolean sentToSettings = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_multiple_permissions);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        permissionStatus = getSharedPreferences("permissionStatus",MODE_PRIVATE);

        txtPermissions = (TextView) findViewById(R.id.txtPermissions);
        btnCheckPermissions = (Button) findViewById(R.id.btnCheckPermissions);

        btnCheckPermissions.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[0]) != PackageManager.PERMISSION_GRANTED
                        || ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[1]) != PackageManager.PERMISSION_GRANTED
                        || ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[2]) != PackageManager.PERMISSION_GRANTED){
                    if(ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[0])
                            || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[1])
                            || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[2])){
                        //Show Information about why you need the permission
                        AlertDialog.Builder builder = new AlertDialog.Builder(MultiplePermissionsActivity.this);
                        builder.setTitle("Need Multiple Permissions");
                        builder.setMessage("This app needs Camera and Location permissions.");
                        builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                                ActivityCompat.requestPermissions(MultiplePermissionsActivity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
                            }
                        });
                        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                            }
                        });
                        builder.show();
                    } else if (permissionStatus.getBoolean(permissionsRequired[0],false)) {
                        //Previously Permission Request was cancelled with 'Dont Ask Again',
                        // Redirect to Settings after showing Information about why you need the permission
                        AlertDialog.Builder builder = new AlertDialog.Builder(MultiplePermissionsActivity.this);
                        builder.setTitle("Need Multiple Permissions");
                        builder.setMessage("This app needs Camera and Location permissions.");
                        builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                                sentToSettings = true;
                                Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
                                Uri uri = Uri.fromParts("package", getPackageName(), null);
                                intent.setData(uri);
                                startActivityForResult(intent, REQUEST_PERMISSION_SETTING);
                                Toast.makeText(getBaseContext(), "Go to Permissions to Grant  Camera and Location", Toast.LENGTH_LONG).show();
                            }
                        });
                        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                            }
                        });
                        builder.show();
                    }  else {
                        //just request the permission
                        ActivityCompat.requestPermissions(MultiplePermissionsActivity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
                    }

                    txtPermissions.setText("Permissions Required");

                    SharedPreferences.Editor editor = permissionStatus.edit();
                    editor.putBoolean(permissionsRequired[0],true);
                    editor.commit();
                } else {
                    //You already have the permission, just go ahead.
                    proceedAfterPermission();
                }
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode == PERMISSION_CALLBACK_CONSTANT){
            //check if all permissions are granted
            boolean allgranted = false;
            for(int i=0;i<grantResults.length;i++){
                if(grantResults[i]==PackageManager.PERMISSION_GRANTED){
                    allgranted = true;
                } else {
                    allgranted = false;
                    break;
                }
            }

            if(allgranted){
                proceedAfterPermission();
            } else if(ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[0])
                    || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[1])
                    || ActivityCompat.shouldShowRequestPermissionRationale(MultiplePermissionsActivity.this,permissionsRequired[2])){
                txtPermissions.setText("Permissions Required");
                AlertDialog.Builder builder = new AlertDialog.Builder(MultiplePermissionsActivity.this);
                builder.setTitle("Need Multiple Permissions");
                builder.setMessage("This app needs Camera and Location permissions.");
                builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                        ActivityCompat.requestPermissions(MultiplePermissionsActivity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
                    }
                });
                builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
                builder.show();
            } else {
                Toast.makeText(getBaseContext(),"Unable to get Permission",Toast.LENGTH_LONG).show();
            }
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_PERMISSION_SETTING) {
            if (ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[0]) == PackageManager.PERMISSION_GRANTED) {
                //Got Permission
                proceedAfterPermission();
            }
        }
    }

    private void proceedAfterPermission() {
        txtPermissions.setText("We've got all permissions");
        Toast.makeText(getBaseContext(), "We got All Permissions", Toast.LENGTH_LONG).show();
    }

    @Override
    protected void onPostResume() {
        super.onPostResume();
        if (sentToSettings) {
            if (ActivityCompat.checkSelfPermission(MultiplePermissionsActivity.this, permissionsRequired[0]) == PackageManager.PERMISSION_GRANTED) {
                //Got Permission
                proceedAfterPermission();
            }
        }
    }

}


Writer : Stuti Kasliwal