PermissionsDispatcher

Library on GitHub with installation instructions:

github.com/permissions-dispatcher/PermissionsDispatcher

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.codinginflow.permissiondispatcherexample.MainActivity">

    <Button
        android:id="@+id/button_open_camera"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="open camera"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.permissiondispatcherexample">

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

    <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/AppTheme">
        <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>

package com.codinginflow.permissiondispatcherexample;

import android.Manifest;
import android.content.DialogInterface;
import android.support.annotation.NonNull;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import permissions.dispatcher.NeedsPermission;
import permissions.dispatcher.OnNeverAskAgain;
import permissions.dispatcher.OnPermissionDenied;
import permissions.dispatcher.OnShowRationale;
import permissions.dispatcher.PermissionRequest;
import permissions.dispatcher.RuntimePermissions;

@RuntimePermissions
public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button buttonOpenCamera = findViewById(R.id.button_open_camera);
        buttonOpenCamera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MainActivityPermissionsDispatcher.openCameraWithPermissionCheck(MainActivity.this);
            }
        });
    }

    @NeedsPermission(Manifest.permission.CAMERA)
    void openCamera() {
        Toast.makeText(this, "Opening Camera", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        MainActivityPermissionsDispatcher.onRequestPermissionsResult(this, requestCode, grantResults);
    }

    @OnShowRationale(Manifest.permission.CAMERA)
    void showRationaleForCamera(final PermissionRequest request) {
        new AlertDialog.Builder(this)
                .setTitle("Permission needed")
                .setMessage("This permission is needed because of this and  that")
                .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        request.proceed();
                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        request.cancel();
                    }
                })
                .show();
    }

    @OnPermissionDenied(Manifest.permission.CAMERA)
    void onCameraDenied() {
        Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show();
    }

    @OnNeverAskAgain(Manifest.permission.CAMERA)
    void onNeverAskAgain() {
        Toast.makeText(this, "Never asking again", Toast.LENGTH_SHORT).show();
    }
}