图片缩放和多点触控

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.zoomimageview.MainActivity" >

    <com.view.ZoomImageView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:scaleType="matrix"
        android:src="@drawable/m3" />

</LinearLayout>

package com.view;

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
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.OnGlobalLayoutListener;
import android.widget.ImageView;
import android.widget.SectionIndexer;

public class ZoomImageView extends ImageView implements OnGlobalLayoutListener,
        OnScaleGestureListener, OnTouchListener {
    private boolean once;
    // 缩放得最小值
    private float minScale;
    // 双击放大值
    private float doubleTouch;
    // 缩放最大值
    private float maxScale;

    private Matrix matrix;
    // 控件的宽高
    private float width;
    private float height;

    private ScaleGestureDetector scaleGestureDetector;

    public ZoomImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        matrix = new Matrix();
        setScaleType(ScaleType.MATRIX);
        scaleGestureDetector = new ScaleGestureDetector(context, this);
        setOnTouchListener(this);
    }

    public ZoomImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

    public void onGlobalLayout() {
        if (!once) {
            // 得到控件的宽和高
            width = getWidth();
            height = getHeight();
            // 得到资源的宽和高
            Drawable drawable = getDrawable();
            int imgWidth = drawable.getIntrinsicWidth();
            int imgHeight = drawable.getIntrinsicHeight();

            float scale = 1.0f;

            if (imgWidth > width && imgHeight < height) {
                scale = width * 1.0f / imgWidth;
            }

            if (imgWidth < width && imgHeight > height) {
                scale = height * 1.0f / imgHeight;
            }

            if ((imgWidth > width && imgHeight > height)
                    || (imgWidth < width && imgHeight < height)) {
                scale = Math.min(width * 1.0f / imgWidth, height * 1.0f
                        / imgHeight);
            }
            minScale = scale;
            maxScale = scale * 4;
// 偏移量
            float dx = width * 1 / 2 - imgWidth * 1 / 2;
            float dy = height * 1 / 2- imgHeight * 1 / 2;
            // 将图片移动到控件的中心
            matrix.postTranslate(dx, dy);
            // 缩放
            matrix.postScale(minScale, minScale, width * 1 / 2, height * 1 / 2);
            setImageMatrix(matrix);

            once = true;

        }

    }

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

    }

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

    // 取得缩放值
    private float getScale() {
        float values[] = new float[9];
        matrix.getValues(values);
        return values[Matrix.MSCALE_X];
    }

    // 将缩放的图片放到矩形中 来获得缩放之后图片的宽高
    private RectF getMatrixRectF() {
        Matrix newmMatrix = matrix;
        RectF rectf = new RectF();
        Drawable drawable = getDrawable();
        if (drawable != null) {
            rectf.set(0, 0, drawable.getIntrinsicWidth(),
                    drawable.getIntrinsicHeight());
            newmMatrix.mapRect(rectf);
        }
        return rectf;
    }

    // 对缩放的位置及边界控制
    private void controlScaleImgState() {
        // 边界空白消除：
        RectF rectf = getMatrixRectF();
        float transX = 0;
        float transY = 0;
        if (width <= rectf.width()) {
            if (rectf.left > 0) {
                transX = -rectf.left;
            }
            if (rectf.right < width) {
                transX = width - rectf.right;
            }
        }
        if (height <= rectf.height()) {
            if (rectf.top > 0) {
                transY = rectf.top;
            }
            if (rectf.bottom < height) {
                transY = height - rectf.bottom;
            }

        }
        
        // 控制居中 当图片小于屏幕
        if (width > rectf.width()) {
            transX = width * 1 / 2 - rectf.right + rectf.width() * 1 / 2;
        }
        if (height > rectf.height()) {
            transY = height * 1 / 2 - rectf.bottom + rectf.height() * 1 / 2;
        }
//设置平移
        matrix.postTranslate(transX, transY);

    }

    // onScaleGestureListener 需要复写的方法
    public boolean onScale(ScaleGestureDetector detector) {
        // 取得当前缩放值
        float scale = getScale();
        // 取得根据手指判断的缩放值
        float scaleFactor = detector.getScaleFactor();
        if (getDrawable() == null) {
            return true;
        }
        // 如果在放大 当前缩放值不大于最大缩放值 或者 如果在缩小 当前缩放值不小于最小缩放值
        if ((scale < maxScale && scaleFactor > 1.0f)
                || (scale > minScale && scaleFactor < 1.0f)) {
            // 如果乘积大于最大值 则设为最大值
            if (scale * scaleFactor > maxScale) {
                scaleFactor = maxScale / scale;
            }
            // 如果乘积小于最小值 则设为最小值
            if (scale * scaleFactor < minScale) {
                scaleFactor = minScale / scale;
            }

            controlScaleImgState();

            matrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(),
                    detector.getFocusX());
            setImageMatrix(matrix);

        }

        return true;
    }

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

    public void onScaleEnd(ScaleGestureDetector detector) {

    }

    // onTouchListener 复写的方法
    public boolean onTouch(View v, MotionEvent event) {
        scaleGestureDetector.onTouchEvent(event);
        return true;
    }

}