Android调用Camera的过程

调用Camera进行拍照的过程

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);
    }
}

获取缩略图

官网上是这样描述的

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.

简而言之就是通过onActivityResult中可以通过getExtras().getdata(“data”)能获取到返回的缩略图，这个缩略图可以很好的用于Icon的显示，但在其他方面使用不是很好。如果想使用图片文件的话，需要将文件保存在本地。

@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);
    }
}

This thumbnail image from “data” might be good for an icon, but not a lot more. Dealing with a full-sized image takes a bit more work.

保存全屏图片

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.

However, if you’d like the photos to remain private to your app only, you can instead use the directory provided by getExternalFilesDir().

我们可以创建私有目录或共有目录来保存图片文件。私有目录只有本APP才能使用，其他应用无法访问，包括Gallery，当应用uninstall后该私有目录也会跟着删除，所以这里我们使用共有目录。

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 + "_";
// 创建私有目录
//File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
// 创建共有目录
File storageDir = Environment.getExternalStoragePublicDirectory(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;
}

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

在此，我们就可以通过以下方法将Camera的文件保存成图片。

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();
        } catch (IOException ex) {
            // Error occurred while creating the File
            ...
        }
        // Continue only if the File was successfully created
        if (photoFile != null) {
            Uri photoUri = Uri.fromFile(photoFile);
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoUri);
            startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO);
        }
    }
}

处理返回的图片文件

在onActivityResult()中可以通过如下的处理来得到图片文件

BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(mPhotoPath, options);
int photoW = options.outWidth;
int photoH = options.outHeight;

int scaleFactor = (int) Math.min(photoW / BitmapUtils.getScaleX(), photoH / BitmapUtils.getScaleY());

options.inJustDecodeBounds = false;
options.inSampleSize = scaleFactor;
options.inPurgeable = true;

Bitmap tempBitmap = BitmapFactory.decodeFile(mPhotoPath, options);
Bitmap bitmap = Bitmap.createScaledBitmap(tempBitmap, (int)BitmapUtils.getScaleX(), (int)BitmapUtils.getScaleY(), true);
tempBitmap.recycle();

mImageView.setBackground(new BitmapDrawable(getResources(), bitmap));

将文件保存到gallery中

到此图片在gallery中还是不可预览的，需要将图片文件插入gallery的数据库中。

private void galleryAddPicture(final String filePath) {
    ContentValues values = new ContentValues();

    values.put(Images.Media.DATE_TAKEN, System.currentTimeMillis());
    values.put(Images.Media.MIME_TYPE, "image/jpg");
    values.put(MediaStore.MediaColumns.DATA, filePath);

    mContext.getContentResolver().insert(Images.Media.EXTERNAL_CONTENT_URI, values);
}