其实android拍照这个地方还是有很多注意事项的，我在上个项目中就遇到一些坑，因此我想把它记录下来，希望能帮助一些跟我遇到的同样的问题的人
如果你在项目中遇到以下问题：
通过系统路径，拍出来的图片不清楚在某些情况下，onActivityResult(int requestCode, int resultCode, Intent data) 回调方法中，data为null有些时候，在某些手机拍照之后会闪退，报空指针错误，等等有些时候在拍完照片之后，点击确认按钮之后，无法返回到前一个Activity可以继续往下看，否则的话，就跳过吧，不能耽误你的时间
先说第一种情况，如果直接调用系统相机，一般系统会把图片放在默认的路径，然后通过回调函数onActivityResult(int requestCode, int resultCode, Intent data)中的data拿值，
Bitmap bitmap =(Bitmap) data.getExtras().get("data"),这样就拿到bitmap了。值得注意的是，返回的这个图片是缩略图并不是原图。如果是需要拍身份证照片，录入信息的，不能用考虑这种。当然这种调用相机也会有人用到，先贴一下代码：
public class MainActivity extends AppCompatActivity {public static final int TAKE_PHOTO = 111;private Button mButton;private ImageView mImageView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mButton = (Button) findViewById(R.id.takePhoto);mImageView = (ImageView) findViewById(R.id.img);mButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {takePhoto();}});}public void takePhoto() {Intent captureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);startActivityForResult(captureIntent, TAKE_PHOTO);}@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);if (resultCode == RESULT_OK) {if (requestCode == TAKE_PHOTO) {Bitmap bitmap = (Bitmap) data.getExtras().get("data");//拿到bitmap，做喜欢做的事情把 ---> 显示 or上传？mImageView.setImageBitmap(bitmap);//upload}}}}
第二种情况，onActivityResult(int requestCode, int resultCode, Intent data) 回调方法中，data为null。这种情况，如果代码没错误，那么产生这种原因是什么呢？ 其实当你自定义拍照路径之后，回调函数中，返回的data就为null了，那么你拿图片资源就只能通过file转化成bitmap的了。下面我会把Bitmap工具类提供出来
public class MainActivity extends AppCompatActivity {public static final int TAKE_PHOTO = 111;private Button mButton;private ImageView mImageView;//保存 照片的目录private String path = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator + "mms";private File photo_file = new File(path);private String photoPath ;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mButton = (Button) findViewById(R.id.takePhoto);mImageView = (ImageView) findViewById(R.id.img);mButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {takePhoto();}});}public void takePhoto() {Intent captureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);if (!photo_file.exists()) {photo_file.mkdirs();}photo_file = new File(path, "/temp.jpg");photoPath = path + "/temp.jpg";if (photo_file != null) {captureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photo_file));startActivityForResult(captureIntent, TAKE_PHOTO);}}@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);if (resultCode == RESULT_OK) {if (requestCode == TAKE_PHOTO) {//这种情况下 data是为null的，因为自定义了路径}}}}
这种情况下，因为data为null，所以正确做法应该是从 photoPath中来获取bitmap。在后面会写出全部代码的，这里只是说明为啥data会为null
在某些手机拍照之后会闪退，报空指针错误。这个错误主要是因为 当点击拍照时，某些情况下，系统会认为这个是耗费资源的操作，所以会未经你允许的情况下把之前的Activity给销毁了，所以当再次回到上个界面中，生命周期会重新来一遍，所以当执行到onActivityResult(int requestCode, int resultCode, Intent data)中，photoPath还是为空，所以报了空指针异常。解决办法如下：
@Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);outState.putString("photoPath", photoPath);Log.d(TAG, "onSaveInstanceState");}@Overrideprotected void onRestoreInstanceState(Bundle savedInstanceState) {super.onRestoreInstanceState(savedInstanceState);if (TextUtils.isEmpty(photoPath)) {photoPath = savedInstanceState.getString("photoPath");}Log.d(TAG, "onRestoreInstanceState");}
通过onSaveInstanceState(Bundle outState)把数据保存起来，然后界面确实被系统销毁了，那么就会执行onRestoreInstanceState(Bundle savedInstanceState)方法，在这个方法中就可以取到数据了，从而恢复界面。
有些时候在拍完照片之后，点击确认按钮之后，无法返回到前一个Activity,这个问题主要是文件建的不对，导入图片资源无法写进去，点击确定后也无法回退到上个界面。这里就按照我这种创建的方式把。
完整拍照上传图片的代码如下：
public class MainActivity extends AppCompatActivity {private static final String TAG = "MainActivity";public static final int TAKE_PHOTO = 111;private Button mButton;private ImageView mImageView;//保存 照片的目录private String path = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator + "mms";private File photo_file = new File(path);private String photoPath;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mButton = (Button) findViewById(R.id.takePhoto);mImageView = (ImageView) findViewById(R.id.img);mButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {takePhoto();}});}public void takePhoto() {Intent captureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);if (!photo_file.exists()) {photo_file.mkdirs();}photo_file = new File(path, "/temp.jpg");photoPath = path + "/temp.jpg";if (photo_file != null) {captureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photo_file));startActivityForResult(captureIntent, TAKE_PHOTO);}}@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);if (resultCode == RESULT_OK) {if (requestCode == TAKE_PHOTO) {//这中情况下 data是为null的，因为自定义了路径 所以通过这个路径来获取Bitmap smallBitmap = BitmapUtil.getSmallBitmap(photoPath);// ok 拿到图片的base64 上传String base64 = BitmapToBase64Util.bitmapToBase64(smallBitmap);}}}@Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);outState.putString("photoPath", photoPath);Log.d(TAG, "onSaveInstanceState");}@Overrideprotected void onRestoreInstanceState(Bundle savedInstanceState) {super.onRestoreInstanceState(savedInstanceState);if (TextUtils.isEmpty(photoPath)) {photoPath = savedInstanceState.getString("photoPath");}Log.d(TAG, "onRestoreInstanceState");}}
BitmapUtil
@SuppressLint("NewApi")public class BitmapUtil {// 计算图片的缩放值public static int calculateInSampleSize(BitmapFactory.Options options,int reqWidth, int reqHeight) {final int height = options.outHeight;final int width = options.outWidth;int inSampleSize = 1;if (height > reqHeight || width > reqWidth) {final int heightRatio = Math.round((float) height/ (float) reqHeight);final int widthRatio = Math.round((float) width / (float) reqWidth);inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;}return inSampleSize;}// 根据路径获得图片并压缩，返回bitmap用于显示public static Bitmap getSmallBitmap(String filePath) {final BitmapFactory.Options options = new BitmapFactory.Options();options.inJustDecodeBounds = true;BitmapFactory.decodeFile(filePath, options);// Calculate inSampleSizeoptions.inSampleSize = calculateInSampleSize(options, 200, 380);// Decode bitmap with inSampleSize setoptions.inJustDecodeBounds = false;return BitmapFactory.decodeFile(filePath, options);}// 根据路径获得图片并压缩，返回bitmap用于显示public static Bitmap getSmallBitmap(InputStream is) {final BitmapFactory.Options options = new BitmapFactory.Options();options.inJustDecodeBounds = true;BitmapFactory.decodeStream(is, null, options);// Calculate inSampleSizeoptions.inSampleSize = calculateInSampleSize(options, 480, 800);// Decode bitmap with inSampleSize setoptions.inJustDecodeBounds = false;return BitmapFactory.decodeStream(is, null, options);}public static Bitmap comp(Bitmap image) {ByteArrayOutputStream baos = new ByteArrayOutputStream();press(pressFormat.JPEG, 100, baos);if (baos.toByteArray().length / 1024 > 1024) {// 判断如果图片大于1M,进行压缩避免在生成图片（BitmapFactory.decodeStream）时溢出baos.reset();// 重置baos即清空press(pressFormat.JPEG, 40, baos);// 这里压缩50%，把压缩后的数据存放到baos中}ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());BitmapFactory.Options newOpts = new BitmapFactory.Options();// 开始读入图片，此时把options.inJustDecodeBounds 设回true了newOpts.inJustDecodeBounds = true;Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);newOpts.inJustDecodeBounds = false;int w = newOpts.outWidth;int h = newOpts.outHeight;// 现在主流手机比较多是800*480分辨率，所以高和宽我们设置为float hh = 800f;// 这里设置高度为800ffloat ww = 480f;// 这里设置宽度为480f// 缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可int be = 1;// be=1表示不缩放if (w > h && w > ww) {// 如果宽度大的话根据宽度固定大小缩放be = (int) (newOpts.outWidth / ww);} else if (w < h && h > hh) {// 如果高度高的话根据宽度固定大小缩放be = (int) (newOpts.outHeight / hh);}if (be <= 0)be = 1;newOpts.inSampleSize = be;// 设置缩放比例// 重新读入图片，注意此时已经把options.inJustDecodeBounds 设回false了isBm = new ByteArrayInputStream(baos.toByteArray());bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);return compressImage(bitmap);// 压缩好比例大小后再进行质量压缩}// 把bitmap转换成Stringpublic static String bitmapToString(String filePath) {Bitmap bm = getSmallBitmap(filePath);ByteArrayOutputStream baos = new ByteArrayOutputStream();press(pressFormat.JPEG, 40, baos);byte[] b = baos.toByteArray();return Base64.encodeToString(b, Base64.DEFAULT);}/*** 质量压缩* @param image* @return*/public static Bitmap compressImage(Bitmap image) {ByteArrayOutputStream baos = new ByteArrayOutputStream();press(pressFormat.JPEG, 50, baos);// 质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中int options = 50;while (baos.toByteArray().length / 1024 > 100) { // 循环判断如果压缩后图片是否大于100kb,大于继续压缩baos.reset();// 重置baos即清空press(pressFormat.JPEG, options, baos);// 这里压缩options%，把压缩后的数据存放到baos中options -= 10;// 每次都减少10}ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把压缩后的数据baos存放到ByteArrayInputStream中Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream数据生成图片return bitmap;}/*** 根据Uri获取图片绝对路径，解决Android4.4以上版本Uri转换* @param context* @param imageUri* @author yaoxing* @date -10-12*/public static String getImageAbsolutePath(Activity context, Uri imageUri) {if (context == null || imageUri == null)return null;if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT && DocumentsContract.isDocumentUri(context, imageUri)) {if (isExternalStorageDocument(imageUri)) {String docId = DocumentsContract.getDocumentId(imageUri);String[] split = docId.split(":");String type = split[0];if ("primary".equalsIgnoreCase(type)) {return Environment.getExternalStorageDirectory() + "/" + split[1];}} else if (isDownloadsDocument(imageUri)) {String id = DocumentsContract.getDocumentId(imageUri);Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));return getDataColumn(context, contentUri, null, null);} else if (isMediaDocument(imageUri)) {String docId = DocumentsContract.getDocumentId(imageUri);String[] split = docId.split(":");String type = split[0];Uri contentUri = null;if ("image".equals(type)) {contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;} else if ("video".equals(type)) {contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;} else if ("audio".equals(type)) {contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;}String selection = MediaStore.Images.Media._ID + "=?";String[] selectionArgs = new String[] { split[1] };return getDataColumn(context, contentUri, selection, selectionArgs);}} // MediaStore (and general)else if ("content".equalsIgnoreCase(imageUri.getScheme())) {// Return the remote addressif (isGooglePhotosUri(imageUri))return imageUri.getLastPathSegment();return getDataColumn(context, imageUri, null, null);}// Fileelse if ("file".equalsIgnoreCase(imageUri.getScheme())) {return imageUri.getPath();}return null;}public static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {Cursor cursor = null;String column = MediaStore.Images.Media.DATA;String[] projection = { column };try {cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);if (cursor != null && cursor.moveToFirst()) {int index = cursor.getColumnIndexOrThrow(column);return cursor.getString(index);}} finally {if (cursor != null)cursor.close();}return null;}/**** 图片的缩放方法** @param bgimage* ：源图片资源* @param newWidth* ：缩放后宽度* @param newHeight* ：缩放后高度* @return*/public static Bitmap zoomImage(Bitmap bgimage, double newWidth,double newHeight) {// 获取这个图片的宽和高float width = bgimage.getWidth();float height = bgimage.getHeight();// 创建操作图片用的matrix对象Matrix matrix = new Matrix();// 计算宽高缩放率float scaleWidth = ((float) newWidth) / width;float scaleHeight = ((float) newHeight) / height;// 缩放图片动作matrix.postScale(scaleWidth, scaleHeight);Bitmap bitmap = Bitmap.createBitmap(bgimage, 0, 0, (int) width,(int) height, matrix, true);return bitmap;}/*** @param uri The Uri to check.* @return Whether the Uri authority is ExternalStorageProvider.*/public static boolean isExternalStorageDocument(Uri uri) {return "com.android.externalstorage.documents".equals(uri.getAuthority());}/*** @param uri The Uri to check.* @return Whether the Uri authority is DownloadsProvider.*/public static boolean isDownloadsDocument(Uri uri) {return "com.android.providers.downloads.documents".equals(uri.getAuthority());}/*** @param uri The Uri to check.* @return Whether the Uri authority is MediaProvider.*/public static boolean isMediaDocument(Uri uri) {return "com.android.providers.media.documents".equals(uri.getAuthority());}/*** @param uri The Uri to check.* @return Whether the Uri authority is Google Photos.*/public static boolean isGooglePhotosUri(Uri uri) {return "com.google.android.apps.photos.content".equals(uri.getAuthority());}}
BitmapUtil工具类主要包含了获取bitmap、质量压缩等一些方法。当然拍照之后一般会获取图片的base64，然后上传给服务端，或者前端js。BitmapToBase64Util代码如下；
BitmapToBase64Util
public class BitmapToBase64Util {/*** bitmapתΪbase64** @param bitmap* @return*/public static String bitmapToBase64(Bitmap bitmap) {String result = null;ByteArrayOutputStream baos = null;try {if (bitmap != null) {baos = new ByteArrayOutputStream();press(pressFormat.JPEG, 50, baos); //这里50表示压缩50%baos.flush();baos.close();byte[] bitmapBytes = baos.toByteArray();result = Base64.encodeToString(bitmapBytes, Base64.DEFAULT);}} catch (Exception e) {e.printStackTrace();} finally {try {if (baos != null) {baos.flush();baos.close();}} catch (Exception e) {e.printStackTrace();}}return result;}/*** base64תΪbitmap** @param base64Data* @return*/public static Bitmap base64ToBitmap(String base64Data) {byte[] bytes = Base64.decode(base64Data, Base64.DEFAULT);return BitmapFactory.decodeByteArray(bytes, 0, bytes.length);}}
