调用相机拍照

官方文档
https://developer.android.com/training/camera/photobasics?hl=zh-cn#java

拍照后的图片如果希望保存再公共存储空间，需要申请权限

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

//获取公共存储空间的方法
File storageDir = getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);

如果是存储在私用空间，对于4.4以下的系统还是要申请权限，对于4.4及以上的系统则不需要，因为其他app访问不了。

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

//获取私有存储空间的方法
File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);

创建文件用于存储拍摄的图片。

String currentPhotoPath;

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
    currentPhotoPath = image.getAbsolutePath();
    return image;
}

发起调用相机Intent

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 = FileProvider.getUriForFile(this,
                                                  "com.example.android.fileprovider",
                                                  photoFile);
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);
            startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO);
        }
    }
}

创建provider组件

<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>

创建res/xml/file_paths.xml文件

<?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>

在onActivityResult中处理拍照结果

 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (requestCode){
            case SELECT_PIC_BY_TACK_PHOTO:

                if (currentPhotoPath != null) {
                    Glide.with(this)
                            .load(currentPhotoPath)
                            .into(imageView);
                }
        }
}

添加到媒体库

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

Decode a scaled image

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

    // Get the dimensions of the bitmap
    BitmapFactory.Options bmOptions = new BitmapFactory.Options();
    bmOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(currentPhotoPath, boptions);
    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(currentPhotoPath, boptions);
    imageView.setImageBitmap(bitmap);
}

遇到的问题：

拍照后调用裁剪崩溃：FileUriExposedException
因为Android 7.0不允许intent带有file://的URI离开自身的应用了，要不然会抛出FileUriExposedException
想要在自己应用和其他应用之间共享File数据，只能使用content://的方式
改成如下：

if (currentPhotoPath != null) {
                    File file = new File(currentPhotoPath);
                    Uri contentUri = FileProvider.getUriForFile(this, "ecp.PhotoPicker", file);
                    cropPic(contentUri);
                }

小米的手机无法调用裁剪功能：

没有打开裁剪界面、没有日志报错。。。

        cropIntent.putExtra("return-data", false);
        cropIntent.putExtra(MediaStore.EXTRA_OUTPUT,photoURI);

调用裁剪Intent时，设为不返回bitmap，而是保存到文件中。
这是可以成功打开裁剪界面了。但是裁剪完，点击确定，又出现一下问题

照片裁剪后点击确定出现： “保存时出现错误，保存失败”

在5.1的设备测试没问题，应该时8.1的存储策略改变了。
保存的uri改成：

        Uri uritempFile = Uri.parse("file://" + "/" + Environment.getExternalStorageDirectory().getPath() + "/" + System.currentTimeMillis() + ".jpg");
        cropIntent.putExtra(MediaStore.EXTRA_OUTPUT, uritempFile);

调用相机拍照后打开裁剪功能： “图片加载失败”

加上这一句就可以了。

        cropIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);