[Android]支援雙指手勢放大縮小移動的ImageView

/*
 * Stan 2013/04/25
 * ver 2.0.8
 */
package com.stan.libs.imageview.scalable;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;

/*
 * @author: Stan
 */
public class StanScalableImageView extends ImageView {

 private Matrix matrix = new Matrix();

 // mode can be in one of these 3 states
 private static final int NONE = 0;
 private static final int DRAG = 1;
 private static final int ZOOM = 2;
 private int mode = NONE;

 private static final int CLICK = 3;

 // Remember some things
 private PointF last = new PointF();
 private PointF start = new PointF();
 private float minScale = 1f;// default
 private float maxScale = 3f;// default
 private float minScaleTemp;// measure
 private float maxScaleTemp;// measure
 private float[] m;
 private float redundantXSpace, redundantYSpace;
 private float width, height;
 private float nowScale = 1f;
 private float origWidth, origHeight, imageWidth, imageHeight,
   redundantWidth, redundantHeight;
 private boolean fit = false;

 private ScaleGestureDetector mScaleDetector;

 public StanScalableImageView(Context context) {
  super(context);
  initStanScalableImageView(context);
 }

 public StanScalableImageView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initStanScalableImageView(context);
 }

 public StanScalableImageView(Context context, AttributeSet attrs,
   int defStyle) {
  super(context, attrs, defStyle);
  initStanScalableImageView(context);
 }

 private void initStanScalableImageView(Context context) {
  super.setScaleType(ScaleType.CENTER);
  mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
  matrix.setTranslate(1f, 1f);
  m = new float[9];
  setImageMatrix(matrix);
  setScaleType(ScaleType.MATRIX);
  setOnTouchListener(new DragListener());
 }

 @Override
 public void setImageBitmap(Bitmap bitmap) {
  super.setImageBitmap(bitmap);
  imageWidth = bitmap.getWidth();
  imageHeight = bitmap.getHeight();
 }

 @Override
 public void setImageDrawable(Drawable drawable) {
  super.setImageDrawable(drawable);
  imageWidth = drawable.getIntrinsicWidth();
  imageHeight = drawable.getIntrinsicHeight();
 }

 @Override
 public void setImageResource(int resourceID) {
  super.setImageResource(resourceID);
  imageWidth = getResources().getDrawable(resourceID).getIntrinsicWidth();
  imageHeight = getResources().getDrawable(resourceID)
    .getIntrinsicHeight();
 }

 public void setMaxZoom(float x) {
  this.maxScale = x;
 }

 public void setMinZoom(float x) {
  this.minScale = x;
 }

 public void setFit(boolean fit) {
  this.fit = fit;
 }
 
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  width = MeasureSpec.getSize(widthMeasureSpec);
  height = MeasureSpec.getSize(heightMeasureSpec);
  float scale;
  if (fit) {
   float scaleX = (float) width / (float) imageWidth;
   float scaleY = (float) height / (float) imageHeight;
   scale = Math.min(scaleX, scaleY);
   matrix.setScale(scale, scale);
  } else {
   scale = 1;
  }
  minScaleTemp = minScale * scale;
  maxScaleTemp = maxScale * scale;

  setImageMatrix(matrix);
  nowScale = scale;

  // Center the image
  redundantHeight = (scale * (float) imageHeight);
  redundantWidth = (scale * (float) imageWidth);
  redundantYSpace = (float) height - (scale * (float) imageHeight);
  redundantXSpace = (float) width - redundantWidth;
  redundantYSpace /= (float) 2;
  redundantXSpace /= (float) 2;

  matrix.getValues(m);
  float x = m[Matrix.MTRANS_X];
  float y = m[Matrix.MTRANS_Y];
  matrix.postTranslate(redundantXSpace - x, redundantYSpace - y);

  origWidth = width - 2 * redundantXSpace;
  origHeight = height - 2 * redundantYSpace;
  setImageMatrix(matrix);
 }

 private class DragListener implements OnTouchListener {

  @Override
  public boolean onTouch(View v, MotionEvent event) {
   mScaleDetector.onTouchEvent(event);
   matrix.getValues(m);
   float x = m[Matrix.MTRANS_X];
   float y = m[Matrix.MTRANS_Y];
   PointF curr = new PointF(event.getX(), event.getY());

   switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
    last.set(event.getX(), event.getY());
    start.set(last);
    if (nowScale * imageWidth > width * 1.05
      || nowScale * imageHeight > height * 1.05) {
     mode = DRAG;
    }
    break;
   case MotionEvent.ACTION_MOVE:
    float deltaX = curr.x - last.x;
    float deltaY = curr.y - last.y;
    if (mode == DRAG) {
     float scaleWidth = Math.round(imageWidth * nowScale);
     float scaleHeight = Math.round(imageHeight * nowScale);
     // x
     if (scaleWidth < width) {// 不超過邊框時置中
      deltaX = redundantXSpace - x
        - (imageWidth * nowScale - redundantWidth) / 2;
     } else {
      if (deltaX > 0 && x + deltaX > 0) {// 往右拉&&左邊拉過頭
       deltaX = -x;
      } else if (deltaX < 0
        && x + deltaX + scaleWidth < width) {// 往左拉&&右邊拉過頭
       deltaX = width - x - scaleWidth;
      }
     }
     // y
     if (scaleHeight < height) {// 不超過邊框時置中
      deltaY = redundantYSpace - y
        - (imageHeight * nowScale - redundantHeight)
        / 2;
     } else {
      if (deltaY > 0 && y + deltaY > 0) {// 往下拉&&上邊拉過頭
       deltaY = -y;
      } else if (deltaY < 0
        && y + deltaY + scaleHeight < height) {// 往上拉&&下邊拉過頭
       deltaY = height - y - scaleHeight;
      }
     }
     matrix.postTranslate(deltaX, deltaY);
     last.set(curr.x, curr.y);
    }
    break;

   case MotionEvent.ACTION_UP:
    mode = NONE;
    int xDiff = (int) Math.abs(curr.x - start.x);
    int yDiff = (int) Math.abs(curr.y - start.y);
    if (xDiff < CLICK && yDiff < CLICK)
     performClick();
    break;

   case MotionEvent.ACTION_POINTER_UP:
    mode = NONE;
    break;
   }
   setImageMatrix(matrix);
   invalidate();
   return true;
  }
 }

 private class ScaleListener extends
   ScaleGestureDetector.SimpleOnScaleGestureListener {
  @Override
  public boolean onScaleBegin(ScaleGestureDetector detector) {
   mode = ZOOM;
   last.set(detector.getFocusX(), detector.getFocusY());
   start.set(last);
   return true;
  }

  @Override
  public boolean onScale(ScaleGestureDetector detector) {
   float mScaleFactor = detector.getScaleFactor();
   float origScale = nowScale;
   nowScale *= mScaleFactor;
   if (nowScale > maxScaleTemp) {
    nowScale = maxScaleTemp;
    mScaleFactor = maxScaleTemp / origScale;
   } else if (nowScale < minScaleTemp) {
    nowScale = minScaleTemp;
    mScaleFactor = minScaleTemp / origScale;
   }
   if (origWidth * nowScale <= width
     || origHeight * nowScale <= height) {
    matrix.postScale(mScaleFactor, mScaleFactor, width / 2,
      height / 2);
   } else {
    matrix.postScale(mScaleFactor, mScaleFactor,
      detector.getFocusX(), detector.getFocusY());
   }
   matrix.getValues(m);
   float x = m[Matrix.MTRANS_X];
   float y = m[Matrix.MTRANS_Y];
   float scaleWidth = Math.round(imageWidth * nowScale);
   float scaleHeight = Math.round(imageHeight * nowScale);
   if (nowScale < origScale) {// 縮小時置中
    if (x > 0 && x + scaleWidth > width) {// 只有左邊有空隙
     matrix.postTranslate(-x, 0);
    } else if (x < 0 && x + scaleWidth < width) {// 只有右邊有空隙
     matrix.postTranslate(width - x - scaleWidth, 0);
    } else if (x > 0 && x + scaleWidth < width) {// 兩邊都有空隙
     matrix.postTranslate((width - scaleWidth) / 2 - x, 0);
    }
    if (y > 0 && y + scaleHeight > height) {// 只有上邊有空隙
     matrix.postTranslate(0, -y);
    } else if (y < 0 && y + scaleHeight < height) {// 只有下邊有空隙
     matrix.postTranslate(0, height - y - scaleHeight);
    } else if (y > 0 && y + scaleHeight < height) {// 兩邊都有空隙
     matrix.postTranslate(0, (height - scaleHeight) / 2 - y);
    }
   }

   PointF curr = new PointF(detector.getFocusX(), detector.getFocusY());
   float deltaX = curr.x - last.x;
   float deltaY = curr.y - last.y;
   last.set(curr.x, curr.y);
   // x
   if (scaleWidth < width) {// 不超過邊框時置中
    deltaX = redundantXSpace - x
      - (imageWidth * nowScale - redundantWidth) / 2;
    return true;// 縮放這邊已經置中過了，跳調
   } else {
    if (deltaX > 0 && x + deltaX > 0) {// 往右拉&&左邊拉過頭
     deltaX = -x;
    } else if (deltaX < 0 && x + deltaX + scaleWidth < width) {// 往左拉&&右邊拉過頭
     deltaX = width - x - scaleWidth;
    }
   }
   // y
   if (scaleHeight < height) {// 不超過邊框時置中
    deltaY = redundantYSpace - y
      - (imageHeight * nowScale - redundantHeight) / 2;
    return true;// 縮放這邊已經置中過了，跳調
   } else {
    if (deltaY > 0 && y + deltaY > 0) {// 往下拉&&上邊拉過頭
     deltaY = -y;
    } else if (deltaY < 0 && y + deltaY + scaleHeight < height) {// 往上拉&&下邊拉過頭
     deltaY = height - y - scaleHeight;
    }
   }
   matrix.postTranslate(deltaX, deltaY);
   return true;
  }
 }
}