android - 图像 Uri 到字节数组

Question

我目前有两个活动。一种用于从 SD 卡中提取图像，另一种用于蓝牙连接。

我使用 Bundle 从活动 1 传输图像的 Uri。

现在我想做的是让蓝牙活动中的 Uri 通过字节数组将其转换为可传输状态我已经看到了一些示例，但我似乎无法让它们为我的代码工作！

Bundle goTobluetooth = getIntent().getExtras();
    test = goTobluetooth.getString("ImageUri");

是我必须克服的。下一步是什么？

Answer 1

从Uri得到byte[]我做以下事情，

InputStream iStream =   getContentResolver().openInputStream(uri);
byte[] inputData = getBytes(iStream);

getBytes(InputStream)方法是：

public byte[] getBytes(InputStream inputStream) throws IOException {
      ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
      int bufferSize = 1024;
      byte[] buffer = new byte[bufferSize];

      int len = 0;
      while ((len = inputStream.read(buffer)) != -1) {
        byteBuffer.write(buffer, 0, len);
      }
      return byteBuffer.toByteArray();
    }

Answer 2

Kotlin 在这里非常简洁：

@Throws(IOException::class)
private fun readBytes(context: Context, uri: Uri): ByteArray? = 
    context.contentResolver.openInputStream(uri)?.buffered()?.use { it.readBytes() }

在 Kotlin 中，他们为InputStreamlike buffered、use和readBytes.

• buffered将输入流装饰为BufferedInputStream
• use处理关闭流
• readBytes完成读取流和写入字节数组的主要工作

错误案例：

• IOException可以在过程中发生（如在 Java 中）
• openInputStream可以返回null。如果您在 Java 中调用该方法，您可以轻松地监督这一点。想想你想如何处理这种情况。

Answer 3

kotlin 中的语法

val inputData = contentResolver.openInputStream(uri)?.readBytes()

Answer 4

Java 最佳实践：永远不要忘记关闭您打开的每个流！这是我的实现：

/**
 * get bytes array from Uri.
 * 
 * @param context current context.
 * @param uri uri fo the file to read.
 * @return a bytes array.
 * @throws IOException
 */
public static byte[] getBytes(Context context, Uri uri) throws IOException {
    InputStream iStream = context.getContentResolver().openInputStream(uri);
    try {
        return getBytes(iStream);
    } finally {
        // close the stream
        try {
            iStream.close();
        } catch (IOException ignored) { /* do nothing */ }
    }
}



 /**
 * get bytes from input stream.
 *
 * @param inputStream inputStream.
 * @return byte array read from the inputStream.
 * @throws IOException
 */
public static byte[] getBytes(InputStream inputStream) throws IOException {

    byte[] bytesResult = null;
    ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
    int bufferSize = 1024;
    byte[] buffer = new byte[bufferSize];
    try {
        int len;
        while ((len = inputStream.read(buffer)) != -1) {
            byteBuffer.write(buffer, 0, len);
        }
        bytesResult = byteBuffer.toByteArray();
    } finally {
        // close the stream
        try{ byteBuffer.close(); } catch (IOException ignored){ /* do nothing */ }
    }
    return bytesResult;
}

Answer 5

use getContentResolver().openInputStream(uri) to get an InputStream from a URI. and then read the data from inputstream convert the data into byte[] from that inputstream

Try with following code

public byte[] readBytes(Uri uri) throws IOException {
          // this dynamically extends to take the bytes you read
        InputStream inputStream = getContentResolver().openInputStream(uri);
          ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();

          // this is storage overwritten on each iteration with bytes
          int bufferSize = 1024;
          byte[] buffer = new byte[bufferSize];

          // we need to know how may bytes were read to write them to the byteBuffer
          int len = 0;
          while ((len = inputStream.read(buffer)) != -1) {
            byteBuffer.write(buffer, 0, len);
          }

          // and then we can return your byte array.
          return byteBuffer.toByteArray();
        }

Refer this LINKs

Answer 6

这段代码对我有用

Uri selectedImage = imageUri;
            getContentResolver().notifyChange(selectedImage, null);
            ImageView imageView = (ImageView) findViewById(R.id.imageView1);
            ContentResolver cr = getContentResolver();
            Bitmap bitmap;
            try {
                 bitmap = android.provider.MediaStore.Images.Media
                 .getBitmap(cr, selectedImage);

                imageView.setImageBitmap(bitmap);
                Toast.makeText(this, selectedImage.toString(),
                        Toast.LENGTH_LONG).show();
                finish();
            } catch (Exception e) {
                Toast.makeText(this, "Failed to load", Toast.LENGTH_SHORT)
                        .show();

                e.printStackTrace();
            }

Answer 7

public void uriToByteArray(String uri)
    {

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(new File(uri));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        byte[] buf = new byte[1024];
        int n;
        try {
            while (-1 != (n = fis.read(buf)))
                baos.write(buf, 0, n);
        } catch (IOException e) {
            e.printStackTrace();
        }
        byte[] bytes = baos.toByteArray();
    }

Answer 8

使用以下方法在 Android Studio中创建一个bytesArrayfrom a 。URI

public byte[] getBytesArrayFromURI(Uri uri) {
    try {
        InputStream inputStream = getContentResolver().openInputStream(uri);
        ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
        int bufferSize = 1024;
        byte[] buffer = new byte[bufferSize];

        int len = 0;
        while ((len = inputStream.read(buffer)) != -1) {
            byteBuffer.write(buffer, 0, len);
        }

        return byteBuffer.toByteArray();

    }catch(Exception e) {
        Log.d("exception", "Oops! Something went wrong.");
    }
    return null;
}