samples/browseable/RuntimePermissionsBasic/src/com.example.android.basicpermissions/camera/CameraPreviewActivity.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.camera;

import com.example.android.basicpermissions.R;

import android.app.Activity;
import android.hardware.Camera;
import android.os.Bundle;
import android.widget.FrameLayout;
import android.widget.Toast;

/**
 * Displays a {@link CameraPreview} of the first {@link Camera}.
 * An error message is displayed if the Camera is not available.
 * <p>
 * This Activity is only used to illustrate that access to the Camera API has been granted (or
 * denied) as part of the runtime permissions model. It is not relevant for the use of the
 * permissions API.
 * <p>
 * Implementation is based directly on the documentation at
 * http://developer.android.com/guide/topics/media/camera.html
 */
public class CameraPreviewActivity extends Activity {

    private static final String TAG = "CameraPreview";

    /**
     * Id of the camera to access. 0 is the first camera.
     */
    private static final int CAMERA_ID = 0;

    private CameraPreview mPreview;
    private Camera mCamera;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Open an instance of the first camera and retrieve its info.
        mCamera = getCameraInstance(CAMERA_ID);
        Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
        Camera.getCameraInfo(CAMERA_ID, cameraInfo);

        if (mCamera == null || cameraInfo == null) {
            // Camera is not available, display error message
            Toast.makeText(this, "Camera is not available.", Toast.LENGTH_SHORT).show();
            setContentView(R.layout.activity_camera_unavailable);
        } else {

            setContentView(R.layout.activity_camera);

            // Get the rotation of the screen to adjust the preview image accordingly.
            final int displayRotation = getWindowManager().getDefaultDisplay()
                    .getRotation();

            // Create the Preview view and set it as the content of this Activity.
            mPreview = new CameraPreview(this, mCamera, cameraInfo, displayRotation);
            FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
            preview.addView(mPreview);
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        // Stop camera access
        releaseCamera();
    }

    /** A safe way to get an instance of the Camera object. */
    private Camera getCameraInstance(int cameraId) {
        Camera c = null;
        try {
            c = Camera.open(cameraId); // attempt to get a Camera instance
        } catch (Exception e) {
            // Camera is not available (in use or does not exist)
            Toast.makeText(this, "Camera " + cameraId + " is not available: " + e.getMessage(),
                    Toast.LENGTH_SHORT).show();
        }
        return c; // returns null if camera is unavailable
    }

    private void releaseCamera() {
        if (mCamera != null) {
            mCamera.release();        // release the camera for other applications
            mCamera = null;
        }
    }
}