图片随手势放大缩小功能

主界面：

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

    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ImageView
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:padding="20dp"
        android:id="@+id/img_init"
        android:src="@drawable/girl"/>

</LinearLayout>

图片放大界面：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    >

    <com.example.test15.picturemanage.ZoomImageView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:scaleType="matrix"
        android:id="@+id/imageurl"
        />
</LinearLayout>

主界面对应的Java文件

package com.example.test15;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;

import com.example.test15.picturemanage.PictureShowActivity;

public class MainActivity extends Activity {
    private ImageView imageView;
    //手指按下的点为x1，手指离开屏幕的点为x2
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView=  findViewById(R.id.img_init);
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,PictureShowActivity.class);
                startActivity(intent);
            }
        });
    }
}

图片放大对应的java文件

package com.example.test15.picturemanage;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.Log;
import android.view.Window;
import android.widget.ImageView;

import com.example.test15.R;

import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
import org.greenrobot.eventbus.ThreadMode;


public class PictureShowActivity extends Activity {
    private ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_picture);

        EventBus.getDefault().register(this);
        imageView=  findViewById(R.id.imageurl);
        Bitmap bitmap=BitmapFactory.decodeResource(getResources(),R.drawable.girl);
        imageView.setImageBitmap(bitmap);
    }

    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onUserEvent(ZooBus zoomBus) {
        Log.d("zoomBus",zoomBus+"");
        finish();
    }
}

图片的处理事件Java文件

package com.example.test15.picturemanage;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Matrix;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.ScaleGestureDetector.OnScaleGestureListener;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewTreeObserver;
import android.widget.ImageView;

import org.greenrobot.eventbus.EventBus;

class ZoomImageView extends ImageView implements OnScaleGestureListener,
        OnTouchListener, ViewTreeObserver.OnGlobalLayoutListener

{
    private static final String TAG = ZoomImageView.class.getSimpleName();
    public static final float SCALE_MAX = 4.0f;
    private static final float SCALE_MID = 2.0f;

    /**
     * 初始化时的缩放比例，如果图片宽或高大于屏幕，此值将小于0
     */
    private float initScale = 1.0f;
    private boolean once = true;

    /**
     * 用于存放矩阵的9个值
     */
    private final float[] matrixValues = new float[9];

    /**
     * 缩放的手势检测
     */
    private ScaleGestureDetector mScaleGestureDetector = null;
    private final Matrix mScaleMatrix = new Matrix();

    /**
     * 用于双击检测
     */
    private GestureDetector mGestureDetector;
    private boolean isAutoScale;

    private int mTouchSlop;

    private float mLastX;
    private float mLastY;

    private boolean isCanDrag;
    private int lastPointerCount;

    private boolean isCheckTopAndBottom = true;
    private boolean isCheckLeftAndRight = true;

    public ZoomImageView(Context context)
    {
        this(context, null);
    }

    public ZoomImageView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        super.setScaleType(ScaleType.MATRIX);
        mGestureDetector = new GestureDetector(context,
                new SimpleOnGestureListener()
                {
                    //单击退出
                    @Override
                    public boolean onSingleTapConfirmed(MotionEvent e) {
                        EventBus.getDefault().post(new ZooBus());
                        return super.onSingleTapConfirmed(e);
                    }


                    //双击放大缩小
                    @Override
                    public boolean onDoubleTap(MotionEvent e)
                    {
                        if (isAutoScale == true)  //首先判断是否正在自动缩放,如果是直接返回true
                            return true;

                        float x = e.getX();
                        float y = e.getY();
                        Log.e("DoubleTap", getScale() + " , " + initScale);
                        //postDelayed每16ms执行一个AutoScaleRunnable方法
                        if (getScale() < SCALE_MID)
                        {
                            ZoomImageView.this.postDelayed(
                                    new AutoScaleRunnable(SCALE_MID, x, y), 16);//如果获得的缩放比例小于SCALE_MID,那么就设置缩放比例为SCALE_MID
                            isAutoScale = true;
                        } else if (getScale() >= SCALE_MID
                                && getScale() < SCALE_MAX)
                        {
                            ZoomImageView.this.postDelayed(
                                    new AutoScaleRunnable(SCALE_MAX, x, y), 16);//如果获得的缩放比例大于SCALE_MID并且小于SCALE_MAX，就设置缩放比例为SCALE_MAX
                            isAutoScale = true;
                        } else
                        {
                            ZoomImageView.this.postDelayed(
                                    new AutoScaleRunnable(initScale, x, y), 16);//同理
                            isAutoScale = true;
                        }

                        return true;
                    }
                });
        mScaleGestureDetector = new ScaleGestureDetector(context, this);   //缩放手势检测
        this.setOnTouchListener(this);  //这个借口主要有onScale()、onScaleBegin()、onScaleEnd()方法
    }

    /**
     * 自动缩放的任务
     *
     * @author zhy
     *
     */
    private class AutoScaleRunnable implements Runnable
    {
        static final float BIGGER = 1.07f;
        static final float SMALLER = 0.93f;
        private float mTargetScale;
        private float tmpScale;

        /**
         * 缩放的中心
         */
        private float x;
        private float y;

        /**
         * 传入目标缩放值，根据目标值与当前值，判断应该放大还是缩小
         *
         * @param targetScale
         */
        public AutoScaleRunnable(float targetScale, float x, float y)
        {
            this.mTargetScale = targetScale;
            this.x = x;
            this.y = y;
            if (getScale() < mTargetScale)
            {
                tmpScale = BIGGER;
            } else
            {
                tmpScale = SMALLER;
            }
        }
        @Override
        public void run()
        {
            // 进行缩放
            mScaleMatrix.postScale(tmpScale, tmpScale, x, y);
            checkBorderAndCenterWhenScale();//如果不用，图片宽高大于屏幕时，图片与屏幕间出现白边；图片小于屏幕，但是不居中。
            setImageMatrix(mScaleMatrix);

            final float currentScale = getScale();
            // 如果值在合法范围内，继续缩放
            if (((tmpScale > 1f) && (currentScale < mTargetScale))
                    || ((tmpScale < 1f) && (mTargetScale < currentScale)))
            {
                Log.d("合理范围",currentScale+" "+mTargetScale+" "+tmpScale);
                ZoomImageView.this.postDelayed(this, 16);
            } else
            // 设置为目标的缩放比例
            {
                Log.d("目标范围","目标范围"+currentScale+" "+mTargetScale);
                final float deltaScale = mTargetScale / currentScale;
                Log.d("deltaScale",deltaScale+" ");
                mScaleMatrix.postScale(deltaScale, deltaScale, x, y);
                checkBorderAndCenterWhenScale();
                setImageMatrix(mScaleMatrix);
                isAutoScale = false;
            }

        }
    }


    //进行缩放，返回值代表缩放事件是否已经被处理
    @SuppressLint("NewApi")
    @Override
    public boolean onScale(ScaleGestureDetector detector)
    {
        Log.d("scale","scale");
        float scale = getScale();//当前已经缩放的缩放比例
        float scaleFactor = detector.getScaleFactor();//通过手势检测检测到的缩放比例

        if (getDrawable() == null)
            return true;


        /**
         * 缩放的范围控制
         */
        if ((scale < SCALE_MAX && scaleFactor > 1.0f)
                || (scale > initScale && scaleFactor < 1.0f))
        {
            /**
             * 最大值最小值判断
             */
            if (scaleFactor * scale < initScale)
            {
                scaleFactor = initScale / scale;
            }
            if (scaleFactor * scale > SCALE_MAX)
            {
                scaleFactor = SCALE_MAX / scale;
            }
            /**
             * 设置缩放比例
             */
            mScaleMatrix.postScale(scaleFactor, scaleFactor,
                    detector.getFocusX(), detector.getFocusY());
            checkBorderAndCenterWhenScale();
            setImageMatrix(mScaleMatrix);
        }
        return true;

    }

    /**
     * 在缩放时，进行图片显示范围的控制
     */
    private void checkBorderAndCenterWhenScale()
    {

        RectF rect = getMatrixRectF();
        float deltaX = 0;
        float deltaY = 0;

        int width = getWidth();
        int height = getHeight();

        // 如果宽或高大于屏幕，则控制范围
        if (rect.width() >= width)
        {
            if (rect.left > 0)
            {
                deltaX = -rect.left;
            }
            if (rect.right < width)
            {
                deltaX = width - rect.right;
            }
        }
        if (rect.height() >= height)
        {
            if (rect.top > 0)
            {
                deltaY = -rect.top;
            }
            if (rect.bottom < height)
            {
                deltaY = height - rect.bottom;
            }
        }
        // 如果宽或高小于屏幕，则让其居中
        if (rect.width() < width)
        {
            deltaX = width * 0.5f - rect.right + 0.5f * rect.width();
        }
        if (rect.height() < height)
        {
            deltaY = height * 0.5f - rect.bottom + 0.5f * rect.height();
        }
        Log.e(TAG, "deltaX = " + deltaX + " , deltaY = " + deltaY);

        mScaleMatrix.postTranslate(deltaX, deltaY);  //deltaX大于0表示向右,deltaY大于0表示向下

    }

    /**
     * 根据当前图片的Matrix获得图片的范围
     *
     * @return
     */
    private RectF getMatrixRectF()
    {
        Matrix matrix = mScaleMatrix;
        RectF rect = new RectF();
        Drawable d = getDrawable();
        if (null != d)
        {
            rect.set(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
            matrix.mapRect(rect);
        }
        return rect;
    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector)
    {
        return true;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector)
    {
    }



    //OnTouchListener接口方法
    @Override
    public boolean onTouch(View v, MotionEvent event)
    {

        if (mGestureDetector.onTouchEvent(event))
            return true;
//    mGestureDetector.onTouchEvent(event);
        mScaleGestureDetector.onTouchEvent(event);

        float x = 0, y = 0;
        // 拿到触摸点的个数
        final int pointerCount = event.getPointerCount();
        // 得到多个触摸点的x与y均值
        for (int i = 0; i < pointerCount; i++)
        {
            x += event.getX(i);
            y += event.getY(i);
        }
        x = x / pointerCount;
        y = y / pointerCount;

        /**
         * 每当触摸点发生变化时，重置mLasX , mLastY
         */
        if (pointerCount != lastPointerCount)
        {
            isCanDrag = false;
            mLastX = x;
            mLastY = y;
        }

        lastPointerCount = pointerCount;
        RectF rectF = getMatrixRectF();
        switch (event.getAction())
        {
//    case MotionEvent.ACTION_DOWN:
//       if (rectF.width() > getWidth() || rectF.height() > getHeight())
//       {
//          getParent().requestDisallowInterceptTouchEvent(true);
//       }
//       break;

            case MotionEvent.ACTION_MOVE:
//       if (rectF.width() > getWidth() || rectF.height() > getHeight())
//       {
//          getParent().requestDisallowInterceptTouchEvent(true);
//       }
                Log.e(TAG, "ACTION_MOVE");
                float dx = x - mLastX;
                float dy = y - mLastY;

                if (!isCanDrag)
                {
                    isCanDrag = isCanDrag(dx, dy);
                }
                if (isCanDrag)
                {
                    if (getDrawable() != null)
                    {
                        // if (getMatrixRectF().left == 0 && dx > 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        //
                        // if (getMatrixRectF().right == getWidth() && dx < 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        isCheckLeftAndRight = isCheckTopAndBottom = true;
                        // 如果宽度小于屏幕宽度，则禁止左右移动
                        if (rectF.width() < getWidth())
                        {
                            dx = 0;
                            isCheckLeftAndRight = false;
                        }
                        // 如果高度小雨屏幕高度，则禁止上下移动
                        if (rectF.height() < getHeight())
                        {
                            dy = 0;
                            isCheckTopAndBottom = false;
                        }


                        mScaleMatrix.postTranslate(dx, dy);
                        checkMatrixBounds();
                        setImageMatrix(mScaleMatrix);
                    }
                }
                mLastX = x;
                mLastY = y;
                break;

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                Log.e(TAG, "ACTION_UP");
                lastPointerCount = 0;
                break;
        }

        return true;
    }

    /**
     * 获得当前的缩放比例
     *
     * @return
     */
    public final float getScale()
    {
        mScaleMatrix.getValues(matrixValues);
//    Log.d("mscale_x", matrixValues[Matrix.MSCALE_X]+ "");
//    Log.d("mscale_y",matrixValues[Matrix.MSCALE_Y]+"");
        return matrixValues[Matrix.MSCALE_X];  //matrixValues[Matrix.MSCALE_X]与matrixValues[Matrix.MSCALE_Y]是一样的
    }

    @Override
    protected void onAttachedToWindow()
    {
        super.onAttachedToWindow();
        getViewTreeObserver().addOnGlobalLayoutListener(this);
    }

    @SuppressWarnings("deprecation")
    @Override
    protected void onDetachedFromWindow()
    {
        super.onDetachedFromWindow();
        getViewTreeObserver().removeGlobalOnLayoutListener(this);
    }


    //根据图片的宽和高以及屏幕的宽和高，对图片进行缩放以及移动至屏幕的中心。如果图片很小，那就正常显示，不放大了~
    @Override
    public void onGlobalLayout()
    {
        if (once)
        {
            Drawable d = getDrawable();
            if (d == null)
                return;
            Log.e(TAG, d.getIntrinsicWidth() + " , " + d.getIntrinsicHeight());
            int width = getWidth();
            int height = getHeight();
            // 拿到图片的宽和高
            int dw = d.getIntrinsicWidth();
            int dh = d.getIntrinsicHeight();
            float scale = 1.0f;
            // 如果图片的宽或者高大于屏幕，则至屏幕的宽或者高
            if (dw > width && dh <= height)
            {
                scale = width * 1.0f / dw;
            }
            if (dh > height && dw <= width)
            {
                scale = height * 1.0f / dh;
            }
            // 如果宽和高都大于屏幕，则让其按按比例适应屏幕大小
            if (dw > width && dh > height)
            {
                scale = Math.min(width * 1.0f / dw, height * 1.0f / dh);
            }
            initScale = scale;

            Log.e(TAG, "initScale = " + initScale);
            mScaleMatrix.postTranslate((width - dw) / 2, (height - dh) / 2);
            mScaleMatrix.postScale(scale, scale, getWidth() / 2,
                    getHeight() / 2);
            // 图片移动至屏幕中心
            setImageMatrix(mScaleMatrix);
            once = false;
        }

    }

    /**
     * 移动时，进行边界判断，主要判断宽或高大于屏幕的
     */
    private void checkMatrixBounds()
    {
        RectF rect = getMatrixRectF();

        float deltaX = 0, deltaY = 0;
        final float viewWidth = getWidth();
        final float viewHeight = getHeight();
        // 判断移动或缩放后，图片显示是否超出屏幕边界
        if (rect.top > 0 && isCheckTopAndBottom)
        {
            deltaY = -rect.top;
        }
        if (rect.bottom < viewHeight && isCheckTopAndBottom)
        {
            deltaY = viewHeight - rect.bottom;
        }
        if (rect.left > 0 && isCheckLeftAndRight)
        {
            deltaX = -rect.left;
        }
        if (rect.right < viewWidth && isCheckLeftAndRight)
        {
            deltaX = viewWidth - rect.right;
        }
        mScaleMatrix.postTranslate(deltaX, deltaY);
    }

    /**
     * 是否是推动行为
     *
     * @param dx
     * @param dy
     * @return
     */
    private boolean isCanDrag(float dx, float dy)
    {
        return Math.sqrt((dx * dx) + (dy * dy)) >= mTouchSlop;
    }
}

package com.example.test15.picturemanage;

public class ZooBus {
}

源码：https://download.csdn.net/download/bcdlxh/10739458