如何在Android Studio中为ImageView添加捏合/双击缩放功能？

方案一：使用PhotoView库（推荐） #

PhotoView是Android生态中最成熟的图片缩放库，原生支持捏合缩放、双击缩放、滑动平移，稳定性远超多数小众库。

步骤1：添加依赖 #

在模块级build.gradle的dependencies块中引入：

implementation 'com.github.chrisbanes:PhotoView:2.3.0'

若使用Android Studio Arctic Fox及以上版本，需在settings.gradle中配置JitPack仓库：

dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
        maven { url 'https://jitpack.io' }
    }
}

步骤2：布局中替换ImageView #

直接用PhotoView替代原生ImageView：

<com.github.chrisbanes.photoview.PhotoView
    android:id="@+id/photo_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/your_target_image" />

步骤3：代码中直接使用 #

无需额外初始化逻辑，默认已支持所有缩放交互：

PhotoView photoView = findViewById(R.id.photo_view);
// 动态设置图片资源
photoView.setImageResource(R.drawable.your_target_image);
// 或设置Bitmap
// photoView.setImageBitmap(yourBitmapObject);

方案二：自定义ImageView实现缩放逻辑 #

如果不想依赖第三方库，可通过处理触摸事件手动实现核心功能：

自定义ZoomImageView代码 #

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;

public class ZoomImageView extends ImageView {
    private Matrix matrix = new Matrix();
    private Matrix savedMatrix = new Matrix();

    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private int touchMode = NONE;

    private ScaleGestureDetector scaleDetector;
    private GestureDetector doubleTapDetector;

    private PointF startPoint = new PointF();
    private PointF midPoint = new PointF();
    private float oldDistance = 1f;

    public ZoomImageView(Context context) {
        super(context);
        init(context);
    }

    public ZoomImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public ZoomImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    private void init(Context context) {
        setScaleType(ScaleType.MATRIX);
        scaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        doubleTapDetector = new GestureDetector(context, new DoubleTapListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        doubleTapDetector.onTouchEvent(event);
        scaleDetector.onTouchEvent(event);

        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                savedMatrix.set(matrix);
                startPoint.set(event.getX(), event.getY());
                touchMode = DRAG;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                oldDistance = calculateDistance(event);
                if (oldDistance > 10f) {
                    savedMatrix.set(matrix);
                    calculateMidPoint(midPoint, event);
                    touchMode = ZOOM;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (touchMode == DRAG) {
                    matrix.set(savedMatrix);
                    matrix.postTranslate(event.getX() - startPoint.x, event.getY() - startPoint.y);
                } else if (touchMode == ZOOM) {
                    float newDistance = calculateDistance(event);
                    if (newDistance > 10f) {
                        matrix.set(savedMatrix);
                        float scale = newDistance / oldDistance;
                        matrix.postScale(scale, scale, midPoint.x, midPoint.y);
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                touchMode = NONE;
                break;
        }
        setImageMatrix(matrix);
        return true;
    }

    private float calculateDistance(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    private void calculateMidPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            float scaleFactor = detector.getScaleFactor();
            matrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
            setImageMatrix(matrix);
            return true;
        }
    }

    private class DoubleTapListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            float[] matrixValues = new float[9];
            matrix.getValues(matrixValues);
            float currentScale = matrixValues[Matrix.MSCALE_X];

            if (currentScale < 2f) {
                matrix.postScale(2f / currentScale, 2f / currentScale, e.getX(), e.getY());
            } else {
                matrix.setScale(1f, 1f);
                float width = getWidth();
                float height = getHeight();
                float imgWidth = getDrawable().getIntrinsicWidth();
                float imgHeight = getDrawable().getIntrinsicHeight();
                float translateX = (width - imgWidth) / 2f;
                float translateY = (height - imgHeight) / 2f;
                matrix.postTranslate(translateX, translateY);
            }
            setImageMatrix(matrix);
            return true;
        }
    }
}

使用自定义View #

在布局中引用：

<com.your.package.name.ZoomImageView
    android:id="@+id/zoom_image_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/your_target_image" />

代码中直接调用：

ZoomImageView zoomImageView = findViewById(R.id.zoom_image_view);
zoomImageView.setImageResource(R.drawable.your_target_image);

注意事项 #

1. 使用PhotoView时，若遇到依赖冲突，可尝试降低版本或排除冲突模块；
2. 自定义View可根据需求添加缩放范围限制（比如最小缩放0.5倍、最大缩放4倍）；
3. 配合Glide/Picasso加载图片时，两种方案均直接兼容，无需额外处理。

内容的提问来源于stack exchange，提问作者Striving Programmer