CameraPreviewActivity.java

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/*
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* Copyright 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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*     http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.android.basicpermissions.camera;
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import com.example.android.basicpermissions.R;
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import android.app.Activity;
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import android.hardware.Camera;
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import android.os.Bundle;
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import android.widget.FrameLayout;
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import android.widget.Toast;
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/**
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 * Displays a {@link CameraPreview} of the first {@link Camera}.
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 * An error message is displayed if the Camera is not available.
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 * <p>
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 * This Activity is only used to illustrate that access to the Camera API has been granted (or
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 * denied) as part of the runtime permissions model. It is not relevant for the use of the
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 * permissions API.
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 * <p>
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 * Implementation is based directly on the documentation at
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 * http://developer.android.com/guide/topics/media/camera.html
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 */
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public class CameraPreviewActivity extends Activity {
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    private static final String TAG = "CameraPreview";
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    /**
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     * Id of the camera to access. 0 is the first camera.
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     */
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    private static final int CAMERA_ID = 0;
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    private CameraPreview mPreview;
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    private Camera mCamera;
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    @Override
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    protected void onCreate(Bundle savedInstanceState) {
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        super.onCreate(savedInstanceState);
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        // Open an instance of the first camera and retrieve its info.
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        mCamera = getCameraInstance(CAMERA_ID);
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        Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
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        Camera.getCameraInfo(CAMERA_ID, cameraInfo);
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        if (mCamera == null || cameraInfo == null) {
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            // Camera is not available, display error message
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            Toast.makeText(this, "Camera is not available.", Toast.LENGTH_SHORT).show();
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            setContentView(R.layout.activity_camera_unavailable);
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        } else {
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            setContentView(R.layout.activity_camera);
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            // Get the rotation of the screen to adjust the preview image accordingly.
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            final int displayRotation = getWindowManager().getDefaultDisplay()
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                    .getRotation();
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            // Create the Preview view and set it as the content of this Activity.
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            mPreview = new CameraPreview(this, mCamera, cameraInfo, displayRotation);
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            FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
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            preview.addView(mPreview);
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        }
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    }
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    @Override
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    public void onPause() {
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        super.onPause();
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        // Stop camera access
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        releaseCamera();
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    }
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    /** A safe way to get an instance of the Camera object. */
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    private Camera getCameraInstance(int cameraId) {
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        Camera c = null;
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        try {
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            c = Camera.open(cameraId); // attempt to get a Camera instance
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        } catch (Exception e) {
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            // Camera is not available (in use or does not exist)
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            Toast.makeText(this, "Camera " + cameraId + " is not available: " + e.getMessage(),
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                    Toast.LENGTH_SHORT).show();
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        }
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        return c; // returns null if camera is unavailable
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    }
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    private void releaseCamera() {
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        if (mCamera != null) {
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            mCamera.release();        // release the camera for other applications
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            mCamera = null;
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        }
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    }
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}
Mar	APR	May
	17
2015	2016	2017
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CameraPreviewActivity.java
