samples/browseable/RuntimePermissionsBasic/src/com.example.android.basicpermissions/MainActivity.java

/*
* Copyright 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.example.android.basicpermissions;

import com.example.android.basicpermissions.camera.CameraPreviewActivity;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.design.widget.Snackbar;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

/**
 * Launcher Activity that demonstrates the use of runtime permissions for Android M.
 * This Activity requests permissions to access the camera
 * ({@link android.Manifest.permission#CAMERA})
 * when the 'Show Camera Preview' button is clicked to start  {@link CameraPreviewActivity} once
 * the permission has been granted.
 * <p>
 * First, the status of the Camera permission is checked using {@link
 * ActivityCompat#checkSelfPermission(Context, String)}
 * If it has not been granted ({@link PackageManager#PERMISSION_GRANTED}), it is requested by
 * calling
 * {@link ActivityCompat#requestPermissions(Activity, String[], int)}. The result of the request is
 * returned to the
 * {@link android.support.v4.app.ActivityCompat.OnRequestPermissionsResultCallback}, which starts
 * {@link
 * CameraPreviewActivity} if the permission has been granted.
 * <p>
 * Note that there is no need to check the API level, the support library
 * already takes care of this. Similar helper methods for permissions are also available in
 * ({@link ActivityCompat},
 * {@link android.support.v4.content.ContextCompat} and {@link android.support.v4.app.Fragment}).
 */
public class MainActivity extends AppCompatActivity
        implements ActivityCompat.OnRequestPermissionsResultCallback {

    private static final int PERMISSION_REQUEST_CAMERA = 0;

    private View mLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mLayout = findViewById(R.id.main_layout);

        // Register a listener for the 'Show Camera Preview' button.
        Button b = (Button) findViewById(R.id.button_open_camera);
        b.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showCameraPreview();
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions,
            int[] grantResults) {
        // BEGIN_INCLUDE(onRequestPermissionsResult)
        if (requestCode == PERMISSION_REQUEST_CAMERA) {
            // Request for camera permission.
            if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Permission has been granted. Start camera preview Activity.
                Snackbar.make(mLayout, "Camera permission was granted. Starting preview.",
                        Snackbar.LENGTH_SHORT)
                        .show();
                startCamera();
            } else {
                // Permission request was denied.
                Snackbar.make(mLayout, "Camera permission request was denied.",
                        Snackbar.LENGTH_SHORT)
                        .show();
            }
        }
        // END_INCLUDE(onRequestPermissionsResult)
    }

    private void showCameraPreview() {
        // BEGIN_INCLUDE(startCamera)
        // Check if the Camera permission has been granted
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                == PackageManager.PERMISSION_GRANTED) {
            // Permission is already available, start camera preview
            Snackbar.make(mLayout,
                    "Camera permission is available. Starting preview.",
                    Snackbar.LENGTH_SHORT).show();
            startCamera();
        } else {
            // Permission is missing and must be requested.
            requestCameraPermission();
        }
        // END_INCLUDE(startCamera)
    }

    /**
     * Requests the {@link android.Manifest.permission#CAMERA} permission.
     * If an additional rationale should be displayed, the user has to launch the request from
     * a SnackBar that includes additional information.
     */
    private void requestCameraPermission() {
        // Permission has not been granted and must be requested.
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.CAMERA)) {
            // Provide an additional rationale to the user if the permission was not granted
            // and the user would benefit from additional context for the use of the permission.
            // Display a SnackBar with a button to request the missing permission.
            Snackbar.make(mLayout, "Camera access is required to display the camera preview.",
                    Snackbar.LENGTH_INDEFINITE).setAction("OK", new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    // Request the permission
                    ActivityCompat.requestPermissions(MainActivity.this,
                            new String[]{Manifest.permission.CAMERA},
                            PERMISSION_REQUEST_CAMERA);
                }
            }).show();

        } else {
            Snackbar.make(mLayout,
                    "Permission is not available. Requesting camera permission.",
                    Snackbar.LENGTH_SHORT).show();
            // Request the permission. The result will be received in onRequestPermissionResult().
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA},
                    PERMISSION_REQUEST_CAMERA);
        }
    }

    private void startCamera() {
        Intent intent = new Intent(this, CameraPreviewActivity.class);
        startActivity(intent);
    }

}