android相册选择图片的编码实现代码

下面我将详细讲解"Android相册选择图片的编码实现代码"的完整攻略。

一、前置知识

在实现"Android相册选择图片的编码"之前，需要掌握一些相关的前置知识，包括：

Android中的Intent机制
Android中的Uri、Bitmap和File类
Android中的图片压缩技巧

二、实现步骤

在掌握了相关的前置知识后，下面我们来讲解"Android相册选择图片的编码实现代码"的具体步骤：

创建一个按钮，点击按钮弹出相册选择图片的窗口。

<Button
    android:id="@+id/btn_select_image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="选择图片" />

在按钮的点击事件中，使用Intent机制启动相册选择图片的界面。

private void selectImage() {
    Intent intent = new Intent();
    intent.setType("image/*");
    intent.setAction(Intent.ACTION_GET_CONTENT);
    startActivityForResult(intent, REQUEST_CODE_SELECT_IMAGE);
}

在onActivityResult()方法中，获取选择的图片路径，并将图片进行压缩。

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_CODE_SELECT_IMAGE && resultCode == RESULT_OK && data != null) {
        Uri selectedImage = data.getData();
        String imagePath = ImageUtils.getRealPathFromUri(this, selectedImage);

        Bitmap bitmap = ImageUtils.getCompressedBitmap(imagePath, 800, 1200);

        // 将压缩过的图片进行编码
        byte[] imageData = ImageUtils.bitmapToByteArray(bitmap);
    }
}

实现相关的工具类，用于获取图片的真实路径、压缩图片和将图片进行编码。

public class ImageUtils {
    /**
     * 获取图片的真实路径
     */
    public static String getRealPathFromUri(Context context, Uri uri) {
        String[] projection = {MediaStore.Images.Media.DATA};
        CursorLoader loader = new CursorLoader(context, uri, projection, null, null, null);
        Cursor cursor = loader.loadInBackground();
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        String result = cursor.getString(column_index);
        cursor.close();
        return result;
    }

    /**
     * 压缩图片
     */
    public static Bitmap getCompressedBitmap(String imagePath, int maxWidth, int maxHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(imagePath, options);
        int width = options.outWidth;
        int height = options.outHeight;
        int inSampleSize = 1;
        while (width > maxWidth || height > maxHeight) {
            width /= 2;
            height /= 2;
            inSampleSize *= 2;
        }
        options.inSampleSize = inSampleSize;
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(imagePath, options);
        return bitmap;
    }

    /**
     * 将Bitmap转换为byte[]
     */
    public static byte[] bitmapToByteArray(Bitmap bitmap) {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }
}

三、示例说明

下面给出两个示例说明，以帮助大家更好地理解具体的实现过程。

示例1：选择图片并显示在ImageView中

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_CODE_SELECT_IMAGE = 1;
    private ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btnSelectImage = findViewById(R.id.btnSelectImage);
        imageView = findViewById(R.id.imageView);

        btnSelectImage.setOnClickListener(v -> selectImage());
    }

    private void selectImage() {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(intent, REQUEST_CODE_SELECT_IMAGE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_CODE_SELECT_IMAGE && resultCode == RESULT_OK && data != null) {
            Uri selectedImage = data.getData();
            String imagePath = getRealPathFromUri(this, selectedImage);

            Bitmap bitmap = getCompressedBitmap(imagePath, 800, 1200);
            imageView.setImageBitmap(bitmap);
        }
    }

    private String getRealPathFromUri(Context context, Uri uri) {
        String[] projection = {MediaStore.Images.Media.DATA};
        CursorLoader loader = new CursorLoader(context, uri, projection, null, null, null);
        Cursor cursor = loader.loadInBackground();
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        String result = cursor.getString(column_index);
        cursor.close();
        return result;
    }

    private Bitmap getCompressedBitmap(String imagePath, int maxWidth, int maxHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(imagePath, options);
        int width = options.outWidth;
        int height = options.outHeight;
        int inSampleSize = 1;
        while (width > maxWidth || height > maxHeight) {
            width /= 2;
            height /= 2;
            inSampleSize *= 2;
        }
        options.inSampleSize = inSampleSize;
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(imagePath, options);
        return bitmap;
    }
}

示例2：选择图片并将图片进行Base64编码

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_CODE_SELECT_IMAGE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btnSelectImage = findViewById(R.id.btnSelectImage);

        btnSelectImage.setOnClickListener(v -> selectImage());
    }

    private void selectImage() {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(intent, REQUEST_CODE_SELECT_IMAGE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_CODE_SELECT_IMAGE && resultCode == RESULT_OK && data != null) {
            Uri selectedImage = data.getData();
            String imagePath = getRealPathFromUri(this, selectedImage);

            Bitmap bitmap = getCompressedBitmap(imagePath, 800, 1200);

            byte[] imageData = bitmapToByteArray(bitmap);
            String encodedImage = Base64.encodeToString(imageData, Base64.DEFAULT);

            Log.d("MainActivity", "Base64编码：" + encodedImage);
        }
    }

    private String getRealPathFromUri(Context context, Uri uri) {
        String[] projection = {MediaStore.Images.Media.DATA};
        CursorLoader loader = new CursorLoader(context, uri, projection, null, null, null);
        Cursor cursor = loader.loadInBackground();
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        String result = cursor.getString(column_index);
        cursor.close();
        return result;
    }

    private Bitmap getCompressedBitmap(String imagePath, int maxWidth, int maxHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(imagePath, options);
        int width = options.outWidth;
        int height = options.outHeight;
        int inSampleSize = 1;
        while (width > maxWidth || height > maxHeight) {
            width /= 2;
            height /= 2;
            inSampleSize *= 2;
        }
        options.inSampleSize = inSampleSize;
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(imagePath, options);
        return bitmap;
    }

    private byte[] bitmapToByteArray(Bitmap bitmap) {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }
}

以上就是"Android相册选择图片的编码实现代码"的完整攻略，希望能够对您有所帮助。

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