我之前的个人项目里, 用到了图片浏览, 大图浏览时, 大多都采用第三方的方案, 但是作为一个开发者,我们也需要知道人家到底是怎么做的. 目前大家普遍用的是Github上 PinchImageView ,或者PhotoView ,我们自己也可以实现一个简单版本的.
以下是我的版本
EnhancedImageView
一个增强的自定义ImageView,具备手势放大缩小等功能,主要原理的是 Matrix + ScaleGestureDetector + GestureDetector 进行对图片进行移动与裁剪
效果图
目前功能有
- 单指滑动 (onTouch)
- 多指滑动 (onTouch)
- 双击放大(GestureDetector onDoubleTap)
- 放大状态双击恢复
- 自由手势放大 (ScaleGestureDetector.OnScaleGestureListener)
- 解决与ViewPager滑动冲突
冲突原因:ViewPager屏蔽了子View的左右移动事件
解决:在放大状态下: getParent().requestDisallowInterceptTouchEvent(true);
只是做了上面那些功能, 但是比如滑动时的惯性效果, 以及缩小到比初始状态还小时的动画恢复等, 都没有做. 正常情况下使用的是Github上体验比较棒的 PinchImageView
难点
- 在拖动时,边界控制,需要每次触摸后都要判断
RectF里面的参数情况 - 放大缩小时的中心点处理
细节很多,需要考虑的东西很多.做出来简单, 做好了很难.
Code
具体工程见: https://github.com/Jerey-Jobs/EnhancedImageView
package com.jerey.imageview;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Matrix;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewTreeObserver;
import android.widget.ImageView;
/**
* OnGlobalLayoutListener 获取控件宽高
*/
public class EnhancedImageView extends ImageView
implements ViewTreeObserver.OnGlobalLayoutListener
, ScaleGestureDetector.OnScaleGestureListener
, View.OnTouchListener {
private static final String TAG = "EnhancedImageView";
private static final boolean DEBUG = true;
//初始化标志
private boolean mInitOnce = false;
//初始化缩放值
private float mInitScale;
private float mMinScale;
//双击放大的值
private float mMidScale;
//放大最大值
private float mMaxScale;
//负责图片的平移缩放
private Matrix mScaleMatrix;
//为缩放而生的类，捕获缩放比例
private ScaleGestureDetector mScaleGestureDetector;
/****************************自由移动***************/
//记录手指数量
private int mLastPointerCount;
//记录上次手指触摸位置
private float mLastX;
private float mLastY;
//触摸移动距离
private int mTouchSlop;
//是否可以拖动
private boolean isCanDrag;
//边界检查时用
private boolean isCheckLeftAndRight;
private boolean isCheckTopAndBottom;
/*****************双击放大********************************/
private GestureDetector mGestureDetector;
public EnhancedImageView(Context context) {
this(context, null);
}
public EnhancedImageView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public EnhancedImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mScaleMatrix = new Matrix();
//覆盖用户设置
super.setScaleType(ScaleType.MATRIX);
mScaleGestureDetector = new ScaleGestureDetector(context, this);
setOnTouchListener(this);
//获取系统默认缩放
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onDoubleTap(MotionEvent e) {
float x = e.getX();
float y = e.getY();
log("当前scale " + getScale() + "mid: " + mMidScale);
if (getScale() < mMidScale) {
mScaleMatrix.postScale(mMidScale/getScale(), mMidScale/getScale(),getWidth()/2,getHeight()/2);
setImageMatrix(mScaleMatrix);
} else {
log("恢复初始化");
//计算将图片移动至中间距离
int dx = getWidth() / 2 - getDrawable().getIntrinsicWidth() / 2;
int dy = getHeight() / 2 - getDrawable().getIntrinsicHeight() / 2;
mScaleMatrix.reset();
mScaleMatrix.postTranslate(dx, dy);
mScaleMatrix.postScale(mInitScale, mInitScale,getWidth()/2,getHeight()/2);
setImageMatrix(mScaleMatrix);
}
return true;
}
});
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
getViewTreeObserver().addOnGlobalLayoutListener(this);
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
getViewTreeObserver().removeGlobalOnLayoutListener(this);
}
/**
* 全局布局完成后会调用
*/
@Override
public void onGlobalLayout() {
if (!mInitOnce) {
//得到控件的宽和高
int width = getWidth();
int height = getHeight();
//拿到图片的宽高
Drawable drawable = getDrawable();
if (drawable == null) {
return;
}
int drawableWidth = drawable.getIntrinsicWidth();
int drawableHeight = drawable.getIntrinsicHeight();
float scale = 1.0f;
//若图片宽度大于控件宽度 高度小于空间高度
if (drawableWidth > width && drawableHeight < height) {
log("若图片宽度大于控件宽度 高度小于空间高度");
scale = width * 1.0f / drawableWidth;
//图片的高度大于控件高度 宽度小于控件宽度
} else if (drawableHeight > height && drawableWidth < width) {
log("图片的高度大于控件高度 宽度小于控件宽度");
scale = height * 1.0f / drawableHeight;
} else if (drawableWidth > width && drawableHeight > height) {
log("都大于");
scale = Math.min(width * 1.0f / drawableWidth, height * 1.0f / drawableHeight);
} else if (drawableWidth < width && drawableHeight < height) {
log("都小于");
scale = Math.min(width * 1.0f / drawableWidth, height * 1.0f / drawableHeight);
}
mInitScale = scale;
mMinScale = scale;
mMidScale = scale * 2;
mMaxScale = scale * 5;
//计算将图片移动至中间距离
int dx = getWidth() / 2 - drawableWidth / 2;
int dy = getHeight() / 2 - drawableHeight / 2;
mScaleMatrix.postTranslate(dx, dy);
//xy方向不变形，必须传一样的
mScaleMatrix.postScale(mInitScale, mInitScale, width / 2, height / 2);
setImageMatrix(mScaleMatrix);
mInitOnce = true;
}
}
/**
* 获取当前图片的缩放值
*
* @return
*/
public float getScale() {
float[] values = new float[9];
mScaleMatrix.getValues(values);
return values[Matrix.MSCALE_X];
}
/**
* 为缩放而生的类：ScaleGestureDetector
*
* @param detector
* @return
*/
@Override
public boolean onScale(ScaleGestureDetector detector) {
float scale = getScale();
float scaleFactor = detector.getScaleFactor();
log("多点触控时候的缩放值: " + scaleFactor);
if (getDrawable() == null) {
return true;
}
//缩放范围的控制, 放大时需要小于最大，缩小时需要大于最小
if ((scale < mMaxScale && scaleFactor > 1.0f) || (scale > mMinScale && scaleFactor < 1.0f)) {
if (scale * scaleFactor < mMinScale) {
scaleFactor = mMinScale / scale;
}
if (scale * scaleFactor > mMaxScale) {
scaleFactor = mMaxScale / scale;
}
log("设置最终缩放值 " + scaleFactor);
mScaleMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
checkBorderForScale();
setImageMatrix(mScaleMatrix);
}
return true;
}
/**
* 获得图片放大缩小以后的宽和高
*
* @return
*/
private RectF getMatrixRectF() {
Matrix matrix = mScaleMatrix;
RectF rectF = new RectF();
Drawable drawable = getDrawable();
if (drawable != null) {
rectF.set(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
//用matrix进行map一下
matrix.mapRect(rectF);
}
return rectF;
}
/**
* 缩放时候进行边界控制等
*/
private void checkBorderForScale() {
RectF rect = getMatrixRectF();
float deltaX = 0;
float deltaY = 0;
int width = getWidth();
int height = getHeight();
if (rect.width() >= width) {
if (rect.left > 0) { //和屏幕左边有空隙
deltaX = -rect.left; //左边移动
}
// 和屏幕as
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;
}
}
//如果宽度或者高度小于控件的宽和高 居中处理
if (rect.width() < width) {
deltaX = getWidth() / 2 - rect.right + rect.width() / 2;
}
if (rect.height() < height) {
deltaY = getHeight() / 2 - rect.bottom + rect.height() / 2;
}
mScaleMatrix.postTranslate(deltaX, deltaY);
}
/**
* 当移动时,进行边界检查.
*/
private void checkBorderForTraslate() {
RectF rectF = getMatrixRectF();
float deltaX = 0;
float deltaY = 0;
int width = getWidth();
int height = getHeight();
//上边有空白,往上移动
if (rectF.top > 0 && isCheckTopAndBottom) {
deltaY = -rectF.top;
}
if (rectF.bottom < height && isCheckTopAndBottom) {
deltaY = height - rectF.bottom;
}
//左边和空白往左边移动
if (rectF.left > 0 && isCheckLeftAndRight) {
deltaX = -rectF.left;
}
if (rectF.right < width && isCheckLeftAndRight) {
deltaX = width - rectF.right;
}
mScaleMatrix.postTranslate(deltaX, deltaY);
}
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector detector) {
}
private void log(String str) {
if (DEBUG) {
Log.i(TAG, str);
}
}
/**
* 为了让mScaleGestureDetector拿到手势
*
* @param v
* @param event
* @return
*/
@Override
public boolean onTouch(View v, MotionEvent event) {
if (mGestureDetector.onTouchEvent(event)) {
return true;
}
mScaleGestureDetector.onTouchEvent(event);
/**
* 计算多指触控中心点
*/
float currentX = 0;
float currentY = 0;
int pointCount = event.getPointerCount();
for (int i = 0; i < pointCount; i++) {
currentX += event.getX(i);
currentY += event.getY(i);
}
currentX /= pointCount;
currentY /= pointCount;
if (mLastPointerCount != pointCount) {
isCanDrag = false;
mLastX = currentX;
mLastY = currentY;
}
mLastPointerCount = pointCount;
RectF rectF = getMatrixRectF();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
//请求不被拦截
if(rectF.width() > getWidth() || rectF.height() > getHeight()){
getParent().requestDisallowInterceptTouchEvent(true);
}
break;
case MotionEvent.ACTION_MOVE:
if(rectF.width() > (getWidth() + 0.01) || rectF.height() > (getHeight() + 0.01)){
getParent().requestDisallowInterceptTouchEvent(true);
}
float dx = currentX - mLastX;
float dy = currentY - mLastY;
if (!isCanDrag) {
isCanDrag = isMoveAction(dx, dy);
}
if (isCanDrag) {
RectF rectf = getMatrixRectF();
if (getDrawable() != null) {
isCheckLeftAndRight = isCheckTopAndBottom = true;
//如果宽度小于控件宽度,不允许横向移动
if (rectf.width() < getWidth()) {
dx = 0;
isCheckLeftAndRight = false;
}
//若高度小于控件高度,不允许纵向移动
if (rectf.height() < getHeight()) {
dy = 0;
isCheckTopAndBottom = false;
}
mScaleMatrix.postTranslate(dx, dy);
checkBorderForTraslate();
setImageMatrix(mScaleMatrix);
}
}
mLastX = currentX;
mLastY = currentY;
break;
//结束时,将手指数量置0
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
mLastPointerCount = 0;
break;
default:
break;
}
return true;
}
/**
* 判断当前移动距离是否大于系统默认最小移动距离
*
* @param dx
* @param dy
* @return
*/
private boolean isMoveAction(float dx, float dy) {
return Math.sqrt(dx * dx + dy * dy) > mTouchSlop;
}
private void resetToInit(){
//得到控件的宽和高
int width = getWidth();
int height = getHeight();
//拿到图片的宽高
Drawable drawable = getDrawable();
if (drawable == null) {
return;
}
int drawableWidth = drawable.getIntrinsicWidth();
int drawableHeight = drawable.getIntrinsicHeight();
float scale = 1.0f;
//若图片宽度大于控件宽度 高度小于空间高度
if (drawableWidth > width && drawableHeight < height) {
log("若图片宽度大于控件宽度 高度小于空间高度");
scale = width * 1.0f / drawableWidth;
//图片的高度大于控件高度 宽度小于控件宽度
} else if (drawableHeight > height && drawableWidth < width) {
log("图片的高度大于控件高度 宽度小于控件宽度");
scale = height * 1.0f / drawableHeight;
} else if (drawableWidth > width && drawableHeight > height) {
log("都大于");
scale = Math.min(width * 1.0f / drawableWidth, height * 1.0f / drawableHeight);
} else if (drawableWidth < width && drawableHeight < height) {
log("都小于");
scale = Math.min(width * 1.0f / drawableWidth, height * 1.0f / drawableHeight);
}
mInitScale = scale;
mMidScale = scale * 2;
mMaxScale = scale * 5;
//计算将图片移动至中间距离
int dx = getWidth() / 2 - drawableWidth / 2;
int dy = getHeight() / 2 - drawableHeight / 2;
mScaleMatrix.postTranslate(dx, dy);
ValueAnimator valueAnimator = new ValueAnimator();
}
}
封面图.png
欢迎star, follow https://github.com/Jerey-Jobs/EnhancedImageView
本文作者：Anderson/Jerey_Jobs
博客地址 ： 夏敏的博客/Anderson大码渣/Jerey_Jobs
简书地址 : Anderson大码渣
github地址 : Jerey_Jobs
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