Android Camera

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Android Camera Preview

The camera is the most visible and most used sensor in an Android device. It is a selling point for most consumers, and the capabilities are getting better with each generation. Image-processing applications normally work on an image after it is taken, but other applications, such as augmented reality, utilize the camera in real-time with overlays.
There are two ways to access the camera from an application.The first is by declaring
an implicit intent.
The implicit intent launches the default camera interface:
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
startActivity(intent);
The second way leverages the Camera class, which provides more flexibility in the settings.This creates a custom camera interface, which is the focus of the examples that follow. Camera hardware access requires explicit permission in the AndroidManifest XML file:
<uses-permission android:name="android.permission.CAMERA" />
This is implied in the following section.

Customizing the Camera

Control of the camera is abstracted into various components in the Android system:

• Camera class—Accesses the camera hardware
• Camera.Parameters class—Specifies the camera parameters such as picture size, picture quality, flash modes, and method to assign Global Positioning System (GPS) location
• Camera Preview methods—Sets the camera output display and toggles streaming video preview to the display
• SurfaceView class—Dedicates a drawing surface at the lowest level of the view hierarchy as a placeholder to display the camera preview

CameraPreviewActivity.java Code

package android.example.camerapreview;

import android.os.Bundle;

import android.app.Activity;

import android.view.Display;

import android.view.Menu;

import android.view.SurfaceView;

import android.view.Window;

public class CameraPreviewActivity extends Activity {

      private int viewWidth = 320;

    private int viewHeight = 240;

           

    private SurfaceView cameraPreview;

           

    @Override

    public void onCreate(Bundle savedInstanceState) {

               

       super.onCreate(savedInstanceState);

       requestWindowFeature(Window.FEATURE_NO_TITLE);

               

       calculateDisplayDimensions();                   

       cameraPreview = new CameraPreview(this);

       setContentView(cameraPreview);

      

    }

           

    private void calculateDisplayDimensions() {

       Display display = getWindowManager().getDefaultDisplay();

       viewWidth = display.getWidth();

       viewHeight = display.getHeight();

    }   

      

}

CameraPreview.java Code

package android.example.camerapreview;

import android.app.Activity;

import android.os.Bundle;

import android.content.Context;

import android.hardware.Camera;

import android.util.Log;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

       

      public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

       

          private SurfaceHolder holder;

          private Camera camera;

       

          public CameraPreview(Context context) {

              super(context);

              holder = getHolder();

              holder.addCallback(this);

              holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

          }

       

          //@Override

          public void surfaceChanged(SurfaceHolder holder2, int format, int w, int h) {

              Camera.Parameters parameters = camera.getParameters();

              parameters.setPreviewSize(w, h);

              camera.setParameters(parameters);

              camera.startPreview();

          }

       

          //@Override

          public void surfaceCreated(SurfaceHolder holder1) {

              try {

                  camera = Camera.open();

                  camera.setPreviewDisplay(holder1);

              }

              catch (Exception e) {

                  Log.i("Exception surfaceCreated()", "e=" + e);

                  camera.release();

                  camera = null;

              }

       

      }

                      

          //@Override

          public void surfaceDestroyed(SurfaceHolder arg0) {

              camera.stopPreview();

              camera.release();

              camera = null;

          }

          

      }

AndroidMainifest.xml Code

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="android.example.camerapreview"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="15" />

    <application

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name=".CameraPreviewActivity"

            android:label="@string/title_activity_camera_preview" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

   

     <!-- We will request access to the camera, saying we require a camera

         of some sort but not one with autofocus capability. -->

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

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

       

    <uses-feature android:name="android.hardware.camera" />

    <uses-feature android:name="android.hardware.camera.autofocus" android:required="false" />

    

</manifest>

Download Android Camera Preview Example code

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Android MediaPlayer

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Android MediaPlayer - Audio

There are two distinct frameworks for recording and playing audio.The choice on which to use depends on the application:

• MediaPlayer/MediaRecorder—This is the standard method to manipulate audio, but must be file- or stream-based data. Creates its own thread for processing. SoundPool utilizes this framework.

• AudioTrack/AudioRecorder—Provides direct access to raw audio. Useful to manipulate audio in memory, write to the buffer while already playing, or any other usage that does not require a file or stream. It does not create its own thread for processing.

These methods are shown in the following section in various recipes.


Choosing and Playing Back Audio Files
The MediaRecorder and MediaPlayer classes are used to record and play back either audio or video.This recipe focuses on audio, and the usage is straightforward. For playback,
the steps are

1. Create an instance of the MediaPlayer:
MediaPlayer m_mediaPlayer = new MediaPlayer();

2. Specify the source of media. It can be created from a raw resource:
m_mediaPlayer = MediaPlayer.create(this, R.raw.my_music);

Another option is to set as a file from the filesystem (which then also needs a prepare statement):
m_mediaPlayer.setDataSource(path);
m_mediaPlayer.prepare();

In any case, these statements need to be surrounded by a try-catch block because the specified resource might not exist.

3. Start playback of the audio:
m_mediaPlayer.start();

4. When the playback is done, stop the MediaPlayer and release the instance to free up resources:
m_mediaPlayer.stop();
m_mediaPlayer.release();

MainActivity.java Code

package android.example.mediaplayer;

import android.os.Bundle;

import android.app.Activity;

import android.content.Intent;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class MainActivity extends Activity {

     

               

          private Button mlocalaudio;

          private Button mresourcesaudio;

          private Button mstreamaudio;

          private static final String MEDIA = "media";

          private static final int LOCAL_AUDIO = 1;

          private static final int STREAM_AUDIO = 2;

          private static final int RESOURCES_AUDIO = 3;

        

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

               

        mlocalaudio = (Button) findViewById(R.id.localaudio);

        mlocalaudio.setOnClickListener(mLocalAudioListener);

        mresourcesaudio = (Button) findViewById(R.id.resourcesaudio);

        mresourcesaudio.setOnClickListener(mResourcesAudioListener);

      

    }

   

    private OnClickListener mLocalAudioListener = new OnClickListener() {

        public void onClick(View v) {

            Intent intent =

                    new Intent(MainActivity.this.getApplication(),

                            MediaPlayerDemo_Audio.class);

            intent.putExtra(MEDIA, LOCAL_AUDIO);

            startActivity(intent);

        }

    };

    private OnClickListener mResourcesAudioListener = new OnClickListener() {

        public void onClick(View v) {

            Intent intent =

                    new Intent(MainActivity.this.getApplication(),

                            MediaPlayerDemo_Audio.class);

            intent.putExtra(MEDIA, RESOURCES_AUDIO);

            startActivity(intent);

        }

    };

 

}

MediaPlayerDemo_Audio.java Code

package android.example.mediaplayer;

import android.app.Activity;

import android.media.MediaPlayer;

import android.os.Bundle;

import android.util.Log;

import android.widget.TextView;

import android.widget.Toast;

public class MediaPlayerDemo_Audio extends Activity {

    private static final String TAG = "MediaPlayerDemo";

    private MediaPlayer mMediaPlayer;

    private static final String MEDIA = "media";

    private static final int LOCAL_AUDIO = 1;

    private static final int STREAM_AUDIO = 2;

    private static final int RESOURCES_AUDIO = 3;

     

    private String path; 

    private TextView tx;

    @Override

    public void onCreate(Bundle icicle) {

        super.onCreate(icicle);

        tx = new TextView(this);

        setContentView(tx);

        Bundle extras = getIntent().getExtras();

        playAudio(extras.getInt(MEDIA));

    }

    private void playAudio(Integer media) {

        try {

            switch (media) {

                case LOCAL_AUDIO:

                    /**

                     * TODO: Set the path variable to a local audio file path.

                     */

                    path = "/sdcard/My Music/test.mp3";

                    if (path == "") {

                        // Tell the user to provide an audio file URL.

                        Toast

                                .makeText(

                                        MediaPlayerDemo_Audio.this,

                                        "Please edit MediaPlayer_Audio Activity, "

                                                + "and set the path variable to your audio file path."

                                                + " Your audio file must be stored on sdcard.",

                                        Toast.LENGTH_LONG).show();

                    }

                    mMediaPlayer = new MediaPlayer();

                    mMediaPlayer.setDataSource(path);

                    mMediaPlayer.prepare();

                    mMediaPlayer.start();

                    break;

                case RESOURCES_AUDIO:

                    /**

                     * TODO: Upload a audio file to res/raw folder and provide

                     * its resid in MediaPlayer.create() method.

                     */

                    mMediaPlayer = MediaPlayer.create(this, R.raw.music);

                    mMediaPlayer.start();

            }

            tx.setText("Playing audio...");

        } catch (Exception e) {

            Log.e(TAG, "error: " + e.getMessage(), e);

        }

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        // TODO Auto-generated method stub

        if (mMediaPlayer != null) {

            mMediaPlayer.release();

            mMediaPlayer = null;

        }

    }

}

activity_main.xml Code

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:background="#FF99FF"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    >

   

    <Button

        android:id="@+id/localaudio"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:textSize="26dp"

        android:layout_marginTop="40dp"

        android:text="Play Audio from Local File" />

   

    <Button

        android:id="@+id/resourcesaudio"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:textSize="26dp"

        android:layout_marginTop="20dp"

        android:text="Play Audio from Resources" />

    <ImageView

        android:id="@+id/imageView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

       

        android:layout_gravity="center_horizontal"

        android:layout_marginTop="20dp"

        android:src="@drawable/android_logo" />

   

</LinearLayout>

Download Android Media Player Example code

Android Control ควบคุมอุปกรณ์ต่างๆ ด้วย Android

http://androidcontrol.blogspot.com

สอนเขียน Android  สอนเขียนโปรแกรม Android

http://androidcontrol.blogspot.com/2012/01/beginning-android-training-android.html

ติดต่อ amphancm@gmail.com