Android Runtime Permissions Example

 XML file 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
<Button
    android:id="@+id/gallery"
    android:text="Open Gallery"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>
    <Button
        android:id="@+id/camera"
        android:text="Open Camera"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <ImageView
        android:id="@+id/imageview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

MaintAcitivity 

public class MainActivity extends AppCompatActivity {
 Button gallery;
 ImageView imageView;
 Button camera;
    private static final int CAMERA_REQUEST = 1888;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gallery = findViewById(R.id.gallery);
        imageView = findViewById(R.id.imageview);
        camera = findViewById(R.id.camera);
        gallery.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                intent.setType("image/*");
                intent.setAction(Intent.ACTION_GET_CONTENT);
                startActivityForResult(Intent.createChooser(intent, "Select image"), 100);

            }
        });
        camera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //permission not grant already
                if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)
                        +ContextCompat.checkSelfPermission(MainActivity.this,Manifest.permission.READ_CONTACTS)
                        +ContextCompat.checkSelfPermission(MainActivity.this,Manifest.permission.READ_EXTERNAL_STORAGE)
                        != PackageManager.PERMISSION_GRANTED) {
                     if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, CAMERA)
                     || ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,READ_CONTACTS)
                     || ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,READ_EXTERNAL_STORAGE))
                     {
                     }else{
                         ActivityCompat.requestPermissions(MainActivity.this,new String[]{CAMERA,READ_CONTACTS,READ_EXTERNAL_STORAGE
                         },CAMERA_REQUEST);
                     }
                }else {
                    // if the permission granted already
                    Intent intent=new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                    startActivity(intent);
                    Toast.makeText(MainActivity.this,"Permission Already Created",Toast.LENGTH_LONG).show();
                }

            }

        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode==CAMERA_REQUEST){
            if (grantResults.length>0 && grantResults[0]==PackageManager.PERMISSION_GRANTED ){
                Toast.makeText(MainActivity.this,"Permission Grandted",Toast.LENGTH_LONG).show();
                Intent intent=new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                startActivity(intent);
            }else {
                Toast.makeText(MainActivity.this,"Permission not Grandted",Toast.LENGTH_LONG).show();
            }
        }
    }
}

Manifiest File used in android
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ansari.gcopen">
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.READ_CONTACTS"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-feature android:name="android.hardware.camera"
        android:required="true" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.GCopen">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>