可缩放图片视图

使用.setImage设置。

package com.example.atry.test50;

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ViewTreeObserver;
import android.widget.ImageView;

import java.io.File;

/**
 * Created by try on 2017/12/6.
 */
public class PictureView extends ImageView {
    private Matrix matrix;
    private PointF prePoint;
    private PointF postPoint;
    private PictureView viewSelf;
    private int viewSelfWidth;
    private int viewSelfHeight;
    private float oldDis;
    private float newDis;
    private float mul;
    private int mode = NONE;
    private static final int NONE = 0;
    private static final int DOU = 2;
    private static final int SIG = 1;

    public PictureView(Context context) {
        super(context);
        matrix = new Matrix();
        viewSelf = this;
        measureRealBulid();
    }

    public PictureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        matrix = new Matrix();
        viewSelf = this;
        measureRealBulid();
    }

    public PictureView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        matrix = new Matrix();
        viewSelf = this;
        measureRealBulid();
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public PictureView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        matrix = new Matrix();
        viewSelf = this;
        measureRealBulid();
    }

    public void setViewSize(int w,int h) {
        viewSelfWidth = w;
        viewSelfHeight = h;
    }

    /*
        获取View的尺寸
     */
    public void measureRealBulid() {
        viewSelf.getViewTreeObserver().addOnPreDrawListener(
                new ViewTreeObserver.OnPreDrawListener() {
                    @Override
                    public boolean onPreDraw() {
                        viewSelf.getViewTreeObserver().removeOnPreDrawListener(this);
                        viewSelfWidth = viewSelf.getWidth();
                        viewSelfHeight = viewSelf.getHeight();
                        Drawable  drawable = viewSelf.getDrawable();
                        if (drawable != null) {
                            matrix.set(viewSelf.getImageMatrix());
                            matrix.postTranslate((viewSelfWidth - drawable.getIntrinsicWidth()) / 2, (viewSelfHeight - drawable.getIntrinsicHeight()) / 2);
                            viewSelf.setImageMatrix(matrix);
                        }
                        return true;
                    }
                }
        );
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN : {
                matrix.set(this.getImageMatrix());
                prePoint = new PointF(event.getX(),event.getY());
                mode = SIG;
            } break;
            case MotionEvent.ACTION_POINTER_DOWN : {
                prePoint = centerPoint(event);
                oldDis = distance(event);
                mode = DOU;
            } break;
            case MotionEvent.ACTION_UP : case MotionEvent.ACTION_POINTER_UP: {
                mode = NONE;
            } break;
            case MotionEvent.ACTION_MOVE: {
                switch (mode) {
                    case NONE : break;
                    case SIG : {
                        matrix.postTranslate(event.getX() - prePoint.x,event.getY() - prePoint.y);
                        prePoint = new PointF(event.getX(),event.getY());
                    } break;
                    case DOU : {
                        postPoint = centerPoint(event);
                        newDis = distance(event);
                        mul = newDis / oldDis;
                        matrix.postTranslate(postPoint.x - prePoint.x,postPoint.y - prePoint.y);
                        matrix.postScale(mul,mul,postPoint.x,postPoint.y);
                        prePoint = postPoint;
                    } break;
                }
            }
        }
        this.setImageMatrix(matrix);
        return true;
    }

    private PointF centerPoint(MotionEvent e) {
       PointF point = new PointF((e.getX(0) + e.getX(1)) / 2,(e.getY(0) + e.getY(1)) / 2);
        return point;
    }

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

    public void setImage(String filePath) {
        File file = new File(filePath);
        if (!file.exists()) return;
        Drawable  drawable;
        BitmapFactory.Options  options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory .decodeFile(filePath,options);
        options.inSampleSize = calculateRealSize(options.outWidth,options.outHeight);
        options.inJustDecodeBounds = false;
        setImageBitmap(BitmapFactory.decodeFile(filePath,options));
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    private int calculateRealSize(int pictureWidth, int pictureHeight) {
        int inSampleSize = 1;
        int realInSampleSize = 1;
        if(viewSelfHeight == 0 || viewSelfWidth == 0) {
            viewSelfWidth = getResources().getConfiguration().screenWidthDp;
            viewSelfHeight = getResources().getConfiguration().screenHeightDp;
        }
        if(viewSelfWidth < pictureWidth && viewSelfHeight >= pictureHeight) {
            inSampleSize = pictureWidth / viewSelfWidth;
        } else if(viewSelfWidth >= pictureWidth && viewSelfHeight < pictureHeight) {
            inSampleSize = pictureHeight / viewSelfHeight;
        } else {
            if(pictureWidth >= pictureHeight) {
                inSampleSize = pictureWidth / viewSelfWidth;
            } else {
                inSampleSize = pictureHeight / viewSelfHeight;
            }
        }
        while(inSampleSize == 0) {
            realInSampleSize -= (inSampleSize & -inSampleSize);
            inSampleSize -= realInSampleSize;
        }
        return realInSampleSize;
    }
}