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;
@Override
protected 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() {
@Override
public void onClick(View view) {
takePhoto();
}
});
}
public void takePhoto() {
Intent captureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(captureIntent, TAKE_PHOTO);
}
@Override
protected 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 ;
@Override
protected 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() {
@Override
public 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);
}
}
@Override
protected 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：
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("photoPath", photoPath);
Log.d(TAG, "onSaveInstanceState");
}
@Override
protected 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;
@Override
protected 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() {
@Override
public 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);
}
}
@Override
protected 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);
}
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("photoPath", photoPath);
Log.d(TAG, "onSaveInstanceState");
}
@Override
protected 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 inSampleSize
options.inSampleSize = calculateInSampleSize(options, 200, 380);
// Decode bitmap with inSampleSize set
options.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 inSampleSize
options.inSampleSize = calculateInSampleSize(options, 480, 800);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeStream(is, null, options);
}
public static Bitmap comp(Bitmap image) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.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baos
image.compress(Bitmap.CompressFormat.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800f
float 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String
public static String bitmapToString(String filePath) {
Bitmap bm = getSmallBitmap(filePath);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.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();
image.compress(Bitmap.CompressFormat.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baos
image.compress(Bitmap.CompressFormat.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 2014-10-12 */
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 address
if (isGooglePhotosUri(imageUri))
return imageUri.getLastPathSegment();
return getDataColumn(context, imageUri, null, null);
}
// File
else 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();
bitmap.compress(Bitmap.CompressFormat.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);
}
}