Taking Photos Simply

Ref : https://developer.android.com/training/camera/photobasics.html

Request Camera Permission

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If an essential function of your application is taking pictures, then restrict its visibility on Google Play to devices that have a camera. To advertise that your application depends on having a camera, put a<uses-feature> tag in your manifest file:

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

If your application uses, but does not require a camera in order to function, instead set android:required to false. In doing so, Google Play will allow devices without a camera to download your application. It's then your responsibility to check for the availability of the camera at runtime by callinghasSystemFeature(PackageManager.FEATURE_CAMERA). If a camera is not available, you should then disable your camera features.

Take a Photo with the Camera App

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The Android way of delegating actions to other applications is to invoke an Intent that describes what you want done. This process involves three pieces: The Intent itself, a call to start the external Activity, and some code to handle the image data when focus returns to your activity.

Here's a function that invokes an intent to capture a photo.

static final int REQUEST_IMAGE_CAPTURE = 1;
private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }
}

Get the Thumbnail

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If the simple feat of taking a photo is not the culmination of your app's ambition, then you probably want to get the image back from the camera application and do something with it.

The Android Camera application encodes the photo in the return Intent delivered to onActivityResult() as a small Bitmap in the extras, under the key"data". The following code retrieves this image and displays it in an ImageView.

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        Bundle extras = data.getExtras();
        Bitmap imageBitmap = (Bitmap) extras.get("data");
        mImageView.setImageBitmap(imageBitmap);
    }
}

Save the Full-size Photo

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The Android Camera application saves a full-size photo if you give it a file to save into. You must provide a fully qualified file name where the camera app should save the photo.

Generally, any photos that the user captures with the device camera should be saved on the device in the public external storage so they are accessible by all apps. The proper directory for shared photos is provided by getExternalStoragePublicDirectory(), with the DIRECTORY_PICTURES argument. Because the directory provided by this method is shared among all apps, reading and writing to it requires the READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE permissions, respectively. The write permission implicitly allows reading, so if you need to write to the external storage then you need to request only one permission:

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

However, if you'd like the photos to remain private to your app only, you can instead use the directory provided by getExternalFilesDir(). On Android 4.3 and lower, writing to this directory also requires the WRITE_EXTERNAL_STORAGE permission. Beginning with Android 4.4, the permission is no longer required because the directory is not accessible by other apps, so you can declare the permission should be requested only on the lower versions of Android by adding the maxSdkVersion attribute:

<manifest ...>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
                     android:maxSdkVersion="18" />
    ...</manifest>

Note: Files you save in the directories provided by getExternalFilesDir() or getFilesDir() are deleted when the user uninstalls your app.

Once you decide the directory for the file, you need to create a collision-resistant file name. You may wish also to save the path in a member variable for later use. Here's an example solution in a method that returns a unique file name for a new photo using a date-time stamp:

String mCurrentPhotoPath;
private File createImageFile() throws IOException {
    // Create an image file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String imageFileName = "JPEG_" + timeStamp + "_";
    File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(
        imageFileName,  /* prefix */
        ".jpg",         /* suffix */
        storageDir      /* directory */
    );

    // Save a file: path for use with ACTION_VIEW intents
    mCurrentPhotoPath = "file:" + image.getAbsolutePath();
    return image;
}

With this method available to create a file for the photo, you can now create and invoke the Intent like this:

static final int REQUEST_TAKE_PHOTO = 1;
private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    // Ensure that there's a camera activity to handle the intent
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        // Create the File where the photo should go
        File photoFile = null;
        try {
            photoFile = createImageFile(); // return File
        } catch (IOException ex) {
            // Error occurred while creating the File
            ...
        }
        // Continue only if the File was successfully created
        if (photoFile != null) {
            Uri photoURI = FileProvider.getUriForFile(this,
                                                  "com.example.android.fileprovider",
                                                  photoFile);
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);
            startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO);
        }
    }
}

Note: We are using getUriForFile(Context, String, File) which returns a content:// URI. For more recent apps targeting Android N and higher, passing a file:// URI across a package boundary causes a FileUriExposedException. Therefore, we now present a more generic way of storing images using a FileProvider.

Now, you need to configure the FileProvider. In your app's manifest, add a provider to your application:

<application>
   ...
   <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="com.example.android.fileprovider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_paths"></meta-data>
    </provider>
    ...</application>

Make sure that the authorities string matches the second argument to getUriForFile(Context, String, File). In the meta-data section of the provider definition, you can see that the provider expects eligible paths to be configured in a dedicated resource file, res/xml/file_paths.xml. Here is the content required for this particular example:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="my_images" path="Android/data/com.example.package.name/files/Pictures" />
</paths>

The path component corresponds to the path that is returned by getExternalFilesDir() when called with Environment.DIRECTORY_PICTURES. Make sure that you replace com.example.package.name with the actual package name of your app. Also, checkout the documentation of FileProvider for an extensive description of path specifiers that you can use besides external-path.

Add the Photo to a Gallery

When you create a photo through an intent, you should know where your image is located, because you said where to save it in the first place. For everyone else, perhaps the easiest way to make your photo accessible is to make it accessible from the system's Media Provider.

Note: If you saved your photo to the directory provided by getExternalFilesDir(), the media scanner cannot access the files because they are private to your app.

The following example method demonstrates how to invoke the system's media scanner to add your photo to the Media Provider's database, making it available in the Android Gallery application and to other apps.

private void galleryAddPic() {
    Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
    File f = new File(mCurrentPhotoPath);
    Uri contentUri = Uri.fromFile(f);
    mediaScanIntent.setData(contentUri);
    this.sendBroadcast(mediaScanIntent);
}

Decode a Scaled Image

Managing multiple full-sized images can be tricky with limited memory. If you find your application running out of memory after displaying just a few images, you can dramatically reduce the amount of dynamic heap used by expanding the JPEG into a memory array that's already scaled to match the size of the destination view. The following example method demonstrates this technique.

private void setPic() {
    // Get the dimensions of the View
    int targetW = mImageView.getWidth();
    int targetH = mImageView.getHeight();

    // Get the dimensions of the bitmap
    BitmapFactory.Options bmOptions = new BitmapFactory.Options();
    bmOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    int photoW = bmOptions.outWidth;
    int photoH = bmOptions.outHeight;

    // Determine how much to scale down the image
    int scaleFactor = Math.min(photoW/targetW, photoH/targetH);

    // Decode the image file into a Bitmap sized to fill the View
    bmOptions.inJustDecodeBounds = false;
    bmOptions.inSampleSize = scaleFactor;
    bmOptions.inPurgeable = true;

    Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    mImageView.setImageBitmap(bitmap);
}

接下來看sample code

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);

mImageView = (ImageView) findViewById(R.id.imageView1);
mVideoView = (VideoView) findViewById(R.id.videoView1);
mImageBitmap = null;
mVideoUri = null;

//  三個button... 同時建立他的listener function

Button picBtn = (Button) findViewById(R.id.btnIntend);
setBtnListenerOrDisable( 
      picBtn, 
      mTakePicOnClickListener,
      MediaStore.ACTION_IMAGE_CAPTURE);

Button picSBtn = (Button) findViewById(R.id.btnIntendS);
setBtnListenerOrDisable( 
      picSBtn, 
      mTakePicSOnClickListener,
      MediaStore.ACTION_IMAGE_CAPTURE);

Button vidBtn = (Button) findViewById(R.id.btnIntendV);
setBtnListenerOrDisable( 
      vidBtn, 
      mTakeVidOnClickListener,
      MediaStore.ACTION_VIDEO_CAPTURE);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.FROYO) {
   mAlbumStorageDirFactory = new FroyoAlbumDirFactory();
} else {
   mAlbumStorageDirFactory = new BaseAlbumDirFactory();
}

}

//  當按下   picBtn  Button  就會呼叫 mTakePicOnClickListener() 

Button.OnClickListener mTakePicOnClickListener = 
   new Button.OnClickListener() {
   @Override   public void onClick(View v) {
      dispatchTakePictureIntent(ACTION_TAKE_PHOTO_B);
   }
};

//  然後就會呼叫 dispatchTakePictureIntent()

private void dispatchTakePictureIntent(int actionCode) {


   //  註冊  ACTION_IMAGE_CAPTURE intent
   Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

   switch(actionCode) {
   case ACTION_TAKE_PHOTO_B: // full size picture
      File f = null;
      
      try {
         f = setUpPhotoFile();
         mCurrentPhotoPath = f.getAbsolutePath();
         takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));
      } catch (IOException e) {
         e.printStackTrace();
         f = null;
         mCurrentPhotoPath = null;
      }
      break;

   default:
      break;       
   } // switch
   startActivityForResult(takePictureIntent, actionCode);
}

private File setUpPhotoFile() throws IOException {
   
   File f = createImageFile();
   mCurrentPhotoPath = f.getAbsolutePath();
   
   return f;
}

private File createImageFile() throws IOException {
   // Create an image file name   String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
   String imageFileName = JPEG_FILE_PREFIX + timeStamp + "_";
   File albumF = getAlbumDir();
   File imageF = File.createTempFile(imageFileName, JPEG_FILE_SUFFIX, albumF);
   return imageF;
}

就跟網站寫的說明差不多的code.....

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