0.前言
最近突發了很多事情，又跟康仔跳票了，無可奈何，不好意思了。最近生活上有很多感悟，一個男人的牛逼就在于平衡工作，學習和家庭，這個點很難把握，既要保證家庭和睦，又要保證自己價值的實現從而避免墮入平庸，每個人的狀況都是不一樣的，沒有什么經驗是可以照搬的，怎么說呢，不斷摸索吧。
1.分析
整個效果是仿照微信來做的,效果如圖所示：
整個效果就是從圖庫選取一張圖片，并進行裁剪，從圖庫選取沒什么好說的，就說說怎么做的裁剪控件吧，這個裁剪控件就是ClipImageView，可以看到它有一個陰影遮罩，一個透明的框，還有圖片的顯示，以及可以移動圖片。
2.代碼
class ClipImageView(context: Context, attributeSet: AttributeSet?) : ImageView(context, attributeSet){ private val paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG) var clipWidth = 300 set(value) { field = value if (isAttachedToWindow) { postInvalidate() } } var clipHeight = 300 set(value) { field = value if (isAttachedToWindow) { postInvalidate() } } var minScale = 1.0f var maxScale = 1.0f private var rectColor = Color.BLACK private var lastTouchX = 0F private var lastTouchY = 0F private val transMatrix = Matrix() private var isTouching = false private var scale = 1.0f var onsaveClipImageListener: OnSaveClipImageListsner? = null private val scaleGestureDetectorListener = object : ScaleGestureDetector.SimpleOnScaleGestureListener() { override fun onScale(detector: ScaleGestureDetector?): Boolean { val curScaleFactor = detector?.scaleFactor ?: 1.0f var curScale = scale * curScaleFactor curScale = if (curScale >= 1.0f) Math.min(maxScale, curScale) else Math.max(minScale, curScale) val scaleFactor = if (curScale > scale) 1 + (curScale - scale) / scale else 1.0f - (scale - curScale) / scale transMatrix.postScale(scaleFactor, scaleFactor, detector?.focusX ?: 0f, detector?.focusY ?: 0f) postInvalidate() scale = curScale return true } override fun onScaleEnd(detector: ScaleGestureDetector?) { super.onScaleEnd(detector) } } private var scaleGestureDetector: ScaleGestureDetector constructor(context: Context) : this(context, null) init { paint.strokeJoin = Paint.Join.ROUND scaleGestureDetector = ScaleGestureDetector(context, scaleGestureDetectorListener) if (attributeSet != null) { pareseAttributeSet(attributeSet) } setBackgroundColor(Color.WHITE) } private fun pareseAttributeSet(attributeSet: AttributeSet) { val typedArray = context.obtainStyledAttributes(attributeSet, R.styleable.ClipImageView) clipWidth = typedArray.getDimensionPixelOffset(R.styleable.ClipImageView_clip_width, clipWidth) clipHeight = typedArray.getDimensionPixelOffset(R.styleable.ClipImageView_clip_width, clipHeight) rectColor = typedArray.getColor(R.styleable.ClipImageView_rect_color, rectColor) minScale = typedArray.getFloat(R.styleable.ClipImageView_min_scale, minScale) maxScale = typedArray.getFloat(R.styleable.ClipImageView_max_scale, maxScale) typedArray.recycle() } override fun layout(l: Int, t: Int, r: Int, b: Int) { super.layout(l, t, r, b) if (clipWidth > measuredWidth) { clipWidth = measuredWidth } if (clipHeight > measuredHeight) { clipHeight = measuredHeight } } override fun onTouchEvent(event: MotionEvent?): Boolean { if (event?.pointerCount ?: 1 >= 2) { isTouching = false return scaleGestureDetector.onTouchEvent(event) } else { when (event?.action) { MotionEvent.ACTION_DOWN -> { isTouching = true lastTouchX = event.x lastTouchY = event.y } MotionEvent.ACTION_MOVE -> { if (isTouching && event.pointerCount == 1) { val offsetX = event.x - lastTouchX val offsetY = event.y - lastTouchY transMatrix.postTranslate(offsetX, offsetY) lastTouchX = event.x lastTouchY = event.y postInvalidate() } } MotionEvent.ACTION_UP -> { isTouching = false } } return true } } override fun onDraw(canvas: Canvas?) { canvas?.let { val saveState = it.saveCount it.save() it.concat(transMatrix) super.onDraw(canvas) it.restoreToCount(saveState) drawMask(it) drawRect(it) } } private fun drawMask(canvas: Canvas) { paint.style = Paint.Style.FILL paint.color = Color.parseColor("#A0000000") canvas.drawRect(0.0f, 0.0f, width.toFloat(), (height / 2 - clipHeight / 2).toFloat(), paint) canvas.drawRect((width / 2 + clipWidth / 2).toFloat(), (height / 2 - clipHeight / 2).toFloat(), width.toFloat(), (height / 2 + clipHeight / 2).toFloat(), paint) canvas.drawRect(0.0f, (height / 2 + clipHeight / 2).toFloat(), width.toFloat(), height.toFloat(), paint) canvas.drawRect(0.0f, (height / 2 - clipHeight / 2).toFloat(), (width / 2 - clipWidth / 2).toFloat(), (height / 2 + clipHeight / 2).toFloat(), paint) } private fun drawRect(canvas: Canvas) { paint.style = Paint.Style.FILL_AND_STROKE paint.color = rectColor paint.strokeWidth = 4.0f val offset = paint.strokeWidth / 2 val left: Float = (width / 2 - clipWidth / 2).toFloat() - offset val top: Float = (height / 2 - clipHeight / 2).toFloat() - offset val right: Float = (width / 2 + clipWidth / 2).toFloat() + offset val bottom: Float = (height / 2 + clipHeight / 2).toFloat() + offset canvas.drawLine(left, top, right, top, paint) canvas.drawLine(right, top, right, bottom, paint) canvas.drawLine(left, bottom, right, bottom, paint) canvas.drawLine(left, top, left, bottom, paint) } interface OnSaveClipImageListsner { fun onImageFinishedSav() } inner class SaveTask(private val filePath: String) : AsyncTask<Unit, Unit, Unit>() { override fun doInBackground(vararg params: Unit?): Unit { saveClipImage(filePath) } override fun onPostExecute(result: Unit?) { super.onPostExecute(result) onsaveClipImageListener?.onImageFinishedSav() } } fun clipAndSaveImage(filePath: String) { SaveTask(filePath).execute() } private fun saveClipImage(filePath: String) { val clipBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888) val clipCanvas = Canvas(clipBitmap) draw(clipCanvas) try { val outputStream = FileOutputStream(filePath) val bitmap = Bitmap.createBitmap(clipBitmap, width / 2 - clipWidth / 2, height / 2 - clipHeight / 2, clipWidth, clipHeight, transMatrix, true) bitmap.compress(Bitmap.CompressFormat.JPEG, 80, outputStream) outputStream.close() } catch (e: IOException) { e.printStackTrace() } }}可以發現這段代碼是繼承自ImageView。
先看代碼段
private fun pareseAttributeSet(attributeSet: AttributeSet) { val typedArray = context.obtainStyledAttributes(attributeSet, R.styleable.ClipImageView) clipWidth = typedArray.getDimensionPixelOffset(R.styleable.ClipImageView_clip_width, clipWidth) clipHeight = typedArray.getDimensionPixelOffset(R.styleable.ClipImageView_clip_width, clipHeight) rectColor = typedArray.getColor(R.styleable.ClipImageView_rect_color, rectColor) minScale = typedArray.getFloat(R.styleable.ClipImageView_min_scale, minScale) maxScale = typedArray.getFloat(R.styleable.ClipImageView_max_scale, maxScale) typedArray.recycle() }這里解析布局文件的里的屬性，其中clipwidth和clipheight分別代表裁剪框的寬度和高度，minScale和maxScale是最小和最大的縮放程度。
override fun layout(l: Int, t: Int, r: Int, b: Int) { super.layout(l, t, r, b) if (clipWidth > measuredWidth) { clipWidth = measuredWidth } if (clipHeight > measuredHeight) { clipHeight = measuredHeight } }在layout方法里設置clipWidth和clipHeight，防止設置值大于控件大小。
drawMask方法和drawRect方法是用來繪制遮罩層和裁剪框的，其中遮罩層就是四個方形，而裁剪框就是一個矩形的外框。
private fun drawMask(canvas: Canvas) { paint.style = Paint.Style.FILL paint.color = Color.parseColor("#A0000000") canvas.drawRect(0.0f, 0.0f, width.toFloat(), (height / 2 - clipHeight / 2).toFloat(), paint) canvas.drawRect((width / 2 + clipWidth / 2).toFloat(), (height / 2 - clipHeight / 2).toFloat(), width.toFloat(), (height / 2 + clipHeight / 2).toFloat(), paint) canvas.drawRect(0.0f, (height / 2 + clipHeight / 2).toFloat(), width.toFloat(), height.toFloat(), paint) canvas.drawRect(0.0f, (height / 2 - clipHeight / 2).toFloat(), (width / 2 - clipWidth / 2).toFloat(), (height / 2 + clipHeight / 2).toFloat(), paint) } private fun drawRect(canvas: Canvas) { paint.style = Paint.Style.FILL_AND_STROKE paint.color = rectColor paint.strokeWidth = 4.0f val offset = paint.strokeWidth / 2 val left: Float = (width / 2 - clipWidth / 2).toFloat() - offset val top: Float = (height / 2 - clipHeight / 2).toFloat() - offset val right: Float = (width / 2 + clipWidth / 2).toFloat() + offset val bottom: Float = (height / 2 + clipHeight / 2).toFloat() + offset canvas.drawLine(left, top, right, top, paint) canvas.drawLine(right, top, right, bottom, paint) canvas.drawLine(left, bottom, right, bottom, paint) canvas.drawLine(left, top, left, bottom, paint) }接著看如何讓圖片隨手指移動和縮放，這里說一下transMatrix，這個是Matrix類，通過它應用到Canvas來實現縮放和移動。
override fun onTouchEvent(event: MotionEvent?): Boolean { if (event?.pointerCount ?: 1 >= 2) { isTouching = false return scaleGestureDetector.onTouchEvent(event) } else { when (event?.action) { MotionEvent.ACTION_DOWN -> { isTouching = true lastTouchX = event.x lastTouchY = event.y } MotionEvent.ACTION_MOVE -> { if (isTouching && event.pointerCount == 1) { val offsetX = event.x - lastTouchX val offsetY = event.y - lastTouchY transMatrix.postTranslate(offsetX, offsetY) lastTouchX = event.x lastTouchY = event.y postInvalidate() } } MotionEvent.ACTION_UP -> { isTouching = false } } return true } }當兩個手指觸摸時，由移動事件有ScaleGestureDetector處理縮放，否則進行移動。
先看移動：
將移動的距離應用到transMatrix，并調用postInvalidate（）重新繪制。
再看縮放處理
private val scaleGestureDetectorListener = object : ScaleGestureDetector.SimpleOnScaleGestureListener() { override fun onScale(detector: ScaleGestureDetector?): Boolean { val curScaleFactor = detector?.scaleFactor ?: 1.0f var curScale = scale * curScaleFactor curScale = if (curScale >= 1.0f) Math.min(maxScale, curScale) else Math.max(minScale, curScale) val scaleFactor = if (curScale > scale) 1 + (curScale - scale) / scale else 1.0f - (scale - curScale) / scale transMatrix.postScale(scaleFactor, scaleFactor, detector?.focusX ?: 0f, detector?.focusY ?: 0f) postInvalidate() scale = curScale return true } override fun onScaleEnd(detector: ScaleGestureDetector?) { super.onScaleEnd(detector) } }在SimpleOnScaleGestureListener的onScale方法處理縮放，將縮放因子應用到transMatrix，并調用postInvalidate（）重新繪制。
接下重點就是onDraw方法：
override fun onDraw(canvas: Canvas?) { canvas?.let { val saveState = it.saveCount it.save() it.concat(transMatrix) super.onDraw(canvas) it.restoreToCount(saveState) drawMask(it) drawRect(it) } }先調用save，保存當前畫布狀態，之后應用transMatrix，縮放和移動畫布，然后調用ImageView的onDraw（）方法，也就是父類的方法，用來繪制圖片，因為繪制遮罩層和裁剪框不移動，所以恢復畫布狀態后進行繪制。
最后就是裁剪圖片了
inner class SaveTask(private val filePath: String) : AsyncTask<Unit, Unit, Unit>() { override fun doInBackground(vararg params: Unit?): Unit { saveClipImage(filePath) } override fun onPostExecute(result: Unit?) { super.onPostExecute(result) onsaveClipImageListener?.onImageFinishedSav() } } fun clipAndSaveImage(filePath: String) { SaveTask(filePath).execute() } private fun saveClipImage(filePath: String) { val clipBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888) val clipCanvas = Canvas(clipBitmap) draw(clipCanvas) try { val outputStream = FileOutputStream(filePath) val bitmap = Bitmap.createBitmap(clipBitmap, width / 2 - clipWidth / 2, height / 2 - clipHeight / 2, clipWidth, clipHeight, transMatrix, true) bitmap.compress(Bitmap.CompressFormat.JPEG, 80, outputStream) outputStream.close() } catch (e: IOException) { e.printStackTrace() } }可以看到啟動了一個AsyncTask用來裁剪和保存Bitmap，其中saveClipImage就是重新構建了一個畫布，并傳入bitmap，重新調用draw方法，將數據信息保存到bitmap，然后裁剪bitmap并存入文件。
3.源碼地址 GitHub
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
新聞熱點
疑難解答
