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

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.example.CustomCropImageView
        android:id="@+id/customCropImageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/buttonPickImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pick Image"
        android:layout_below="@id/customCropImageView" />

    <Button
        android:id="@+id/buttonCrop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Crop"
        android:layout_toEndOf="@id/buttonPickImage"
        android:layout_below="@id/customCropImageView" />

    <Button
        android:id="@+id/buttonCancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Cancel"
        android:layout_toEndOf="@id/buttonCrop"
        android:layout_below="@id/customCropImageView" />

    <Button
        android:id="@+id/buttonSave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        android:layout_toEndOf="@id/buttonCancel"
        android:layout_below="@id/customCropImageView" />
</RelativeLayout>

```java
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.FrameLayout;

public class CustomCropImageView extends FrameLayout {

    // 成員變量定義
    private Bitmap mBitmap; // 要裁剪的圖片
    private Matrix mMatrix = new Matrix(); // 用于變換（縮放、旋轉(zhuǎn)）圖像的矩陣
    private RectF mRect = new RectF(); // 定義裁剪框的位置和大小
    private float[] mLastTouchPos = new float[2]; // 上次觸摸位置，用于計(jì)算移動(dòng)距離
    private float[] mCurrentPos = new float[2]; // 當(dāng)前觸摸位置，用于更新圖像位置
    private float mRotation = 0f; // 圖像的旋轉(zhuǎn)角度
    private boolean mIsDragging = false; // 標(biāo)記是否正在拖動(dòng)圖像
    private ScaleGestureDetector mScaleDetector; // 檢測(cè)多點(diǎn)觸控縮放手勢(shì)
    private GestureDetector mGestureDetector; // 檢測(cè)單點(diǎn)觸控手勢(shì)（如點(diǎn)擊）

    // 構(gòu)造函數(shù)，初始化自定義視圖
    public CustomCropImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 初始化手勢(shì)檢測(cè)器
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        mGestureDetector = new GestureDetector(context, new GestureListener());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (mBitmap != null) {
            // 繪制背景蒙層，使非裁剪區(qū)域變暗
            drawOverlay(canvas);

            // 保存當(dāng)前Canvas狀態(tài)，以便稍后恢復(fù)
            canvas.save();
            // 將Canvas原點(diǎn)移動(dòng)到裁剪框中心，進(jìn)行旋轉(zhuǎn)操作
            canvas.translate(mRect.centerX(), mRect.centerY());
            canvas.rotate(mRotation);
            // 移回原點(diǎn)以繪制旋轉(zhuǎn)后的圖像
            canvas.translate(-mRect.centerX(), -mRect.centerY());
            // 使用變換矩陣?yán)L制圖像
            canvas.drawBitmap(mBitmap, mMatrix, null);
            // 恢復(fù)Canvas到之前的狀態(tài)
            canvas.restore();

            // 繪制裁剪框，讓用戶知道哪里會(huì)被裁剪
            drawCropBox(canvas);
        }
    }

    private void drawOverlay(Canvas canvas) {
        Paint paint = new Paint();
        // 設(shè)置半透明黑色作為蒙層顏色
        paint.setColor(Color.argb(128, 0, 0, 0));
        // 填充整個(gè)視圖為半透明黑色
        canvas.drawRect(0, 0, getWidth(), getHeight(), paint);

        // 創(chuàng)建一個(gè)路徑，添加裁剪框形狀
        Path path = new Path();
        path.addRect(mRect, Path.Direction.CW);
        // 使用canvas.clipPath剪切出裁剪框區(qū)域，使其透明
        // 注意：Region.Op.DIFFERENCE在API 26以上已被棄用，應(yīng)考慮使用其他方式實(shí)現(xiàn)相同效果
        canvas.clipPath(path, Region.Op.DIFFERENCE);
        canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
    }

    private void drawCropBox(Canvas canvas) {
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); // 抗鋸齒
        paint.setStyle(Paint.Style.STROKE); // 只繪制邊框，不填充內(nèi)部
        paint.setStrokeWidth(5); // 邊框?qū)挾?
        paint.setColor(Color.BLUE); // 裁剪框顏色設(shè)置為藍(lán)色
        // 繪制裁剪框矩形
        canvas.drawRect(mRect, paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 分別將事件傳遞給縮放和手勢(shì)檢測(cè)器
        mScaleDetector.onTouchEvent(event);
        mGestureDetector.onTouchEvent(event);

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // 記錄按下時(shí)的坐標(biāo)，開(kāi)始拖動(dòng)
                mLastTouchPos[0] = event.getX();
                mLastTouchPos[1] = event.getY();
                mIsDragging = true;
                break;
            case MotionEvent.ACTION_MOVE:
                if (mIsDragging) {
                    // 更新當(dāng)前位置，并根據(jù)位移調(diào)整矩陣和平移裁剪框
                    mCurrentPos[0] = event.getX();
                    mCurrentPos[1] = event.getY();
                    updateMatrix();
                    invalidate(); // 請(qǐng)求重新繪制界面
                }
                break;
            case MotionEvent.ACTION_UP:
                // 結(jié)束拖動(dòng)
                mIsDragging = false;
                break;
        }
        return true;
    }

    private void updateMatrix() {
        // 更新矩陣以反映圖像的新位置
        mMatrix.setTranslate(mCurrentPos[0] - mLastTouchPos[0], mCurrentPos[1] - mLastTouchPos[1]);
        // 同步裁剪框的位置
        mRect.offset(mCurrentPos[0] - mLastTouchPos[0], mCurrentPos[1] - mLastTouchPos[1]);
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            // 獲取縮放因子并應(yīng)用到矩陣上，保持縮放中心點(diǎn)不變
            float scaleFactor = detector.getScaleFactor();
            mMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
            invalidate(); // 請(qǐng)求重繪以反映變化
            return true;
        }
    }

    private class GestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            // 雙擊時(shí)重置所有變換
            resetTransformations();
            return true;
        }
    }

    private void resetTransformations() {
        // 重置矩陣和旋轉(zhuǎn)角度，以及裁剪框位置
        mMatrix.reset();
        mRotation = 0f;
        mRect.set(/* default values */);
        invalidate(); // 請(qǐng)求重繪
    }

    // 設(shè)置要裁剪的圖片
    public void setImageBitmap(Bitmap bitmap) {
        mBitmap = bitmap;
        // 根據(jù)新圖片尺寸調(diào)整裁剪框大小
        updateCropBoxSize();
        requestLayout(); // 請(qǐng)求布局更新
        invalidate(); // 請(qǐng)求重繪
    }

    private void updateCropBoxSize() {
        // 根據(jù)所選圖片的尺寸設(shè)置合適的裁剪框大小
        int width = mBitmap.getWidth();
        int height = mBitmap.getHeight();
        float aspectRatio = (float) width / height;

        // 設(shè)定裁剪框的初始尺寸為圖片的中心區(qū)域，同時(shí)確保其寬高比與原始圖片一致
        float rectWidth = Math.min(getWidth(), getHeight() * aspectRatio);
        float rectHeight = Math.min(getHeight(), getWidth() / aspectRatio);
        mRect.set((getWidth() - rectWidth) / 2, (getHeight() - rectHeight) / 2, (getWidth() + rectWidth) / 2, (getHeight() + rectHeight) / 2);
    }

    // 獲取裁剪后的圖片
    public Bitmap getCroppedBitmap() {
        // 創(chuàng)建一個(gè)新的位圖來(lái)容納裁剪結(jié)果
        Bitmap croppedBitmap = Bitmap.createBitmap(
            (int)mRect.width(),
            (int)mRect.height(),
            Bitmap.Config.ARGB_8888
        );
        Canvas canvas = new Canvas(croppedBitmap);
        // 平移畫布以對(duì)齊裁剪框左上角
        canvas.translate(-mRect.left, -mRect.top);
        // 繪制變換后的原始圖片到新的位圖中
        canvas.drawBitmap(mBitmap, mMatrix, null);
        return croppedBitmap;
    }
}

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private static final int PICK_IMAGE_REQUEST = 1;
    private static final int REQUEST_PERMISSIONS = 2;
    private CustomCropImageView customCropImageView;
    private Uri imageUri;

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

        customCropImageView = findViewById(R.id.customCropImageView);

        // 檢查并請(qǐng)求存儲(chǔ)權(quán)限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE},
                    REQUEST_PERMISSIONS);
        }

        findViewById(R.id.buttonPickImage).setOnClickListener(v -> pickImage());
        findViewById(R.id.buttonCrop).setOnClickListener(v -> cropImage());
        findViewById(R.id.buttonCancel).setOnClickListener(v -> cancelCrop());
        findViewById(R.id.buttonSave).setOnClickListener(v -> saveImage());
    }

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

    private void cropImage() {
        // 如果使用第三方庫(kù)如uCrop，可以在這里啟動(dòng)裁剪活動(dòng)
        // 這里我們假設(shè)CustomCropImageView已經(jīng)包含了所有裁剪功能
        // 因此不需要啟動(dòng)新的活動(dòng)。
    }

    private void cancelCrop() {
        // 重置CustomCropImageView的狀態(tài)
        customCropImageView.resetTransformations();
    }

    private void saveImage() {
        Bitmap bitmap = customCropImageView.getCroppedBitmap(); // 獲取裁剪后的位圖
        try {
            File path = new File(getExternalFilesDir(null), "custom_folder");
            if (!path.exists()) {
                path.mkdirs();
            }
            File file = new File(path, "cropped_image.jpg");
            FileOutputStream out = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
            out.flush();
            out.close();
            // 提示用戶圖片已保存
        } catch (IOException e) {
            e.printStackTrace();
            // 處理保存失敗的情況
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null && data.getData() != null) {
            imageUri = data.getData();
            try {
                // 將選擇的圖片加載到CustomCropImageView中
                Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), imageUri);
                customCropImageView.setImageBitmap(bitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_PERMISSIONS) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 權(quán)限授予成功，可以繼續(xù)進(jìn)行圖片選擇等操作
            } else {
                // 用戶拒絕了權(quán)限，需要提示用戶或者禁用相關(guān)功能
            }
        }
    }
}