HarmonyOS - 本地相册的纠葛

//展示图片
<Image
    ohos:id="$+id:show_photo"
    ohos:height="200fp"
    ohos:width="200fp"
    ohos:image_src="$media:empty"
    ohos:scale_mode="zoom_center"
    ohos:top_margin="30fp"
    /> 
 //选择图片     
<Text
    ohos:id="$+id:select_photo"
    ohos:height="match_content"
    ohos:width="match_content"
    ohos:background_element="$graphic:background_ability_main"
    ohos:layout_alignment="horizontal_center"
    ohos:text="选择图片"
    ohos:text_size="20vp"
    ohos:top_margin="10fp"
    />
  //保存图片
<Text
    ohos:top_margin="10fp"
    ohos:id="$+id:save_photo"
    ohos:height="match_content"
    ohos:width="match_content"
    ohos:background_element="$graphic:background_ability_main"
    ohos:layout_alignment="horizontal_center"
    ohos:text="保存图片"
    ohos:text_size="20vp"
    />

"reqPermissions": [
  {"name": "ohos.permission.READ_USER_STORAGE"},
  {"name": "ohos.permission.WRITE_USER_STORAGE"}
]

String[] permissions = {"ohos.permission.READ_USER_STORAGE", "ohos.permission.WRITE_USER_STORAGE"};
requestPermissionsFromUser(permissions, 0);

 //保存图片到相册 fileName文件名  PixelMap 图片数据
private void saveImageToLibrary(String fileName, PixelMap pixelMap) {
    try {
        ValuesBucket valuesBucket = new ValuesBucket();
        //文件名
        valuesBucket.putString(AVStorage.Images.Media.DISPLAY_NAME, fileName);
       //相对路径
        valuesBucket.putString("relative_path", "DCIM/");
       //文件格式，类型要一定要注意要是JPEG，PNG类型不支持
        valuesBucket.putString(AVStorage.Images.Media.MIME_TYPE, "image/JPEG");
        //应用独占：is_pending设置为1时表示只有该应用能访问此图片，其他应用无法发现该图片，当图片处理操作完成后再吧is_pending设置为0，解除独占，让其他应用可见
        valuesBucket.putInteger("is_pending", 1);       
      //鸿蒙的helper.insert方法和安卓的contentResolver.insert方法有所不同，安卓方法直接返回一个uri，我们就可以拿来直接操作，而鸿蒙方法返回官方描述是Returns the index of the inserted data record（返回插入的数据记录的索引），这个index我的理解就是id，因此，我们需要自己在后面拼出文件的uri再进行操作
        DataAbilityHelper helper = DataAbilityHelper.creator(this);
        int index = helper.insert(AVStorage.Images.Media.EXTERNAL_DATA_ABILITY_URI, valuesBucket);
        Uri uri = Uri.appendEncodedPathToUri(AVStorage.Images.Media.EXTERNAL_DATA_ABILITY_URI, String.valueOf(index));     
        //获取到uri后，安卓通过contentResolver.openOutputStream(uri)就能获取到输出流来写文件，而鸿蒙没有提供这样的方法，我们就只能通过uri获取FileDescriptor，再通过FileDescriptor生成输出流打包编码成新的图片文件，这里helper.openFile方法一定要有“w”写模式，不然会报FileNotFound的错误。
        FileDescriptor fd = helper.openFile(uri, "w");
        ImagePacker imagePacker = ImagePacker.create();
        ImagePacker.PackingOptions packingOptions = new ImagePacker.PackingOptions();
        OutputStream outputStream = new FileOutputStream(fd);
        packingOptions.format = "image/jpeg";
        packingOptions.quality = 90;
        boolean result = imagePacker.initializePacking(outputStream, packingOptions);
        if (result) {
            result = imagePacker.addImage(pixelMap);
            if (result) {
                long dataSize = imagePacker.finalizePacking();
            }
        }
        outputStream.flush();
        outputStream.close();
        valuesBucket.clear();
        //解除独占
        valuesBucket.putInteger("is_pending", 0);
        helper.update(uri, valuesBucket, null);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

"reqPermissions": [{"name": "ohos.permission.READ_USER_STORAGE"}]

String[] permissions = {"ohos.permission.READ_USER_STORAGE"};
requestPermissionsFromUser(permissions, 0);

//选择图片
 private void selectPhoto() {
        //调起系统的选择来源数据视图
        Intent intent = new Intent();
        Operation opt=new Intent.OperationBuilder().withAction("android.intent.action.GET_CONTENT").build();
        intent.setOperation(opt);
        intent.addFlags(Intent.FLAG_NOT_OHOS_COMPONENT);
        intent.setType("image/*");
        startAbilityForResult(intent, imgRequestCode);
    }

/*选择图片回调*/
@Override
protected void onAbilityResult(int requestCode, int resultCode, Intent resultData) {
    if(requestCode==imgRequestCode && resultData!=null)
    {
        //选择的Img对应的Uri
        String chooseImgUrl=resultData.getUriString();
        //定义数据能力帮助对象
        DataAbilityHelper helper=DataAbilityHelper.creator(getContext());
        //定义图片来源对象
        ImageSource imageSource = null;
        //获取选择的Img对应的Id
        String chooseImgId=null;
        //如果是选择文件则getUriString结果为dataability:///com.android.providers.media.documents/document/image%3A437，其中%3A437是":"的URL编码结果，后面的数字就是image对应的Id
        //如果选择的是图库则getUriString结果为dataability:///media/external/images/media/262，最后就是image对应的Id
        //这里需要判断是选择了文件还是图库
        if(chooseImgUri.lastIndexOf("%3A")!=-1){
            chooseImgId = chooseImgUri.substring(chooseImgUri.lastIndexOf("%3A")+3);
        }
        else {
            chooseImgId = chooseImgUri.substring(chooseImgUri.lastIndexOf('/')+1);
        }
        //获取图片对应的uri，由于获取到的前缀是content，我们替换成对应的dataability前缀
        Uri uri=Uri.appendEncodedPathToUri(AVStorage.Images.Media.EXTERNAL_DATA_ABILITY_URI,chooseImgId);
        try {
            //读取图片
            FileDescriptor fd = helper.openFile(uri, "r");
            imageSource = ImageSource.create(fd, null);
            //创建位图
            PixelMap pixelMap = imageSource.createPixelmap(null);
            //设置图片控件对应的位图
            photo.setPixelMap(pixelMap);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (imageSource != null) {
                imageSource.release();
            }
        }
    }
}