Training—Capturing Photos

阅读:https://developer.android.com/training/camera/index.html

先学学怎么从相机获取相片。

首先要有权限：

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

private void dispatchTakePictureIntent(int actionCode) {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    startActivityForResult(takePictureIntent, actionCode);
}

//查询是否有程序能够照相
public static boolean isIntentAvailable(Context context, String action) {
    final PackageManager packageManager = context.getPackageManager();
    final Intent intent = new Intent(action);
    List<ResolveInfo> list =
            packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
    return list.size() > 0;
}

//获取Bitmap并显示
private void handleSmallCameraPhoto(Intent intent) {
    Bundle extras = intent.getExtras();
    mImageBitmap = (Bitmap) extras.get("data");
    mImageView.setImageBitmap(mImageBitmap);
}

//保存图像
storageDir = new File(
    Environment.getExternalStoragePublicDirectory(
        Environment.DIRECTORY_PICTURES
    ), 
    getAlbumName()
);        
//或者用下面的目录 
storageDir = new File (
    Environment.getExternalStorageDirectory()
        + PICTURES_DIR
        + getAlbumName()
);

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 image = File.createTempFile(
        imageFileName, 
        JPEG_FILE_SUFFIX, 
        getAlbumDir()
    );
    mCurrentPhotoPath = image.getAbsolutePath();
    return image;
}

如果要向INTENT存放图片数据，用：

File f = createImageFile();
takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));

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);
}

下面展示了如何实现缩略图功能（可减少内存使用）：

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);
}

 官方接下来的内容还展示了如何获取录下的视频以及相机的控制，请自行查看。

 

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官方还提供了一些基础的组件让你显示图片还有HTML：

https://developer.android.com/training/printing/index.html