{"id":2008,"date":"2023-04-01T11:45:12","date_gmt":"2023-04-01T03:45:12","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=2008"},"modified":"2023-04-07T10:38:33","modified_gmt":"2023-04-07T02:38:33","slug":"how-android-loads-100mb-of-images-without-bursting-memory","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/04\/01\/how-android-loads-100mb-of-images-without-bursting-memory\/","title":{"rendered":"Android\u5982\u4f55\u52a0\u8f7d100M\u7684\u56fe\u7247\u5374\u4e0d\u6491\u7206\u5185\u5b58"},"content":{"rendered":"<h2>\u9762\u8bd5\u9898<\/h2>\n<ol>\n<li>\u56fe\u7247\u7684\u4e09\u7ea7\u7f13\u5b58\u4e2d\uff0c\u56fe\u7247\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\uff0c\u5982\u679c\u5185\u5b58\u5feb\u7206\u4e86\uff0c\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1f\u600e\u4e48\u5904\u7406\uff1f<\/li>\n<li>\u5185\u5b58\u4e2d\u5982\u679c\u52a0\u8f7d\u4e00\u5f20 500*500 \u7684 png \u9ad8\u6e05\u56fe\u7247\uff0c\u5e94\u8be5\u662f\u5360\u7528\u591a\u5c11\u7684\u5185\u5b58\uff1f<\/li>\n<li>Bitmap \u5982\u4f55\u5904\u7406\u5927\u56fe\uff0c\u5982\u4e00\u5f20 30M \u7684\u5927\u56fe\uff0c\u5982\u4f55\u9884\u9632 OOM\uff1f<\/li>\n<\/ol>\n<p><!-- more --><\/p>\n<p>Android\u5f00\u53d1\u4e2d\uff0c\u6709\u65f6\u5019\u4f1a\u6709\u52a0\u8f7d\u5de8\u56fe\u7684\u9700\u6c42\uff0c\u5982\u4f55\u52a0\u8f7d\u4e00\u4e2a\u5927\u56fe\u800c\u4e0d\u4ea7\u751f<code>OOM<\/code>\u5462\uff0c\u4f7f\u7528\u7cfb\u7edf\u63d0\u4f9b\u7684<code>BitmapRegionDecoder<\/code>\u8fd9\u4e2a\u7c7b\u53ef\u4ee5\u5f88\u8f7b\u677e\u7684\u5b8c\u6210\u3002<\/p>\n<p><code>BitmapRegionDecoder<\/code>\uff1a\u533a\u57df\u89e3\u7801\u5668\uff0c\u53ef\u4ee5\u7528\u6765\u89e3\u7801\u4e00\u4e2a\u77e9\u5f62\u533a\u57df\u7684\u56fe\u50cf\uff0c\u6709\u4e86\u8fd9\u4e2a\u6211\u4eec\u5c31\u53ef\u4ee5\u81ea\u5b9a\u4e49\u4e00\u5757\u77e9\u5f62\u7684\u533a\u57df\uff0c\u7136\u540e\u6839\u636e\u624b\u52bf\u6765\u79fb\u52a8\u77e9\u5f62\u533a\u57df\u7684\u4f4d\u7f6e\u5c31\u80fd\u6162\u6162\u770b\u5230\u6574\u5f20\u56fe\u7247\u4e86\u3002<\/p>\n<p>\u6838\u5fc3\u539f\u7406\u5c31\u662f\u8fd9\u4e48\u7b80\u5355\uff0c\u4e0d\u8fc7\u505a\u8d77\u6765\u8fd8\u662f\u6709\u4e00\u4e9b\u7ec6\u8282\u5904\u7406\uff0c\u4e0b\u9762\u5c31\u4e00\u6b65\u4e00\u6b65\u7684\u5b8c\u6210\u4e00\u4e2a\u52a0\u8f7d\u5927\u56fe\uff0c\u652f\u6301\u62d6\u52a8\u67e5\u770b\uff0c\u53cc\u51fb\u653e\u5927\uff0c\u624b\u52bf\u7f29\u653e\u7684\u7684\u81ea\u5b9a\u4e49View\u3002<\/p>\n<h2>\u5927\u56fe\u52a0\u8f7d\u5b9e\u73b0<\/h2>\n<h3>\u521d\u59cb\u5316\u53d8\u91cf<\/h3>\n<pre><code class=\"language-java\">private void init() {\n    mOptions = new BitmapFactory.Options();\n    \/\/\u6ed1\u52a8\u5668\n    mScroller = new Scroller(getContext());\n    \/\/\u6240\u653e\u5668\n    mMatrix = new Matrix();\n    \/\/\u624b\u52bf\u8bc6\u522b\n    mGestureDetector = new GestureDetector(getContext(), this);\n    mScaleGestureDetector = new ScaleGestureDetector(getContext(), this);\n}<\/code><\/pre>\n<p><code>BitmapFactory.Options<\/code>\u6211\u4eec\u5f88\u719f\u6089\uff0c\u7528\u6765\u914d\u7f6e<code>Bitmap<\/code>\u76f8\u5173\u7684\u53c2\u6570\uff0c\u6bd4\u5982\u83b7\u53d6<code>Bitmap<\/code>\u7684\u5bbd\u9ad8\uff0c\u5185\u5b58\u590d\u7528\u7b49\u53c2\u6570\u3002<\/p>\n<p><code>GestureDetector<\/code>\u7528\u6765\u8bc6\u522b\u53cc\u51fb\u4e8b\u4ef6\uff0c<code>ScaleGestureDetector<\/code>\u7528\u6765\u76d1\u542c\u624b\u6307\u7684\u7f29\u653e\u4e8b\u4ef6\uff0c\u90fd\u662f\u7cfb\u7edf\u63d0\u4f9b\u7684\u7c7b\uff0c\u6bd4\u8f83\u65b9\u4fbf\u4f7f\u7528\u3002<\/p>\n<h3>\u8bbe\u7f6e\u9700\u8981\u52a0\u8f7d\u7684\u56fe\u7247<\/h3>\n<pre><code class=\"language-java\">public void setImage(InputStream is) {\n    mOptions.inJustDecodeBounds = true;\n    BitmapFactory.decodeStream(is, null, mOptions);\n    mImageWidth = mOptions.outWidth;\n    mImageHeight = mOptions.outHeight;\n    mOptions.inPreferredConfig = Bitmap.Config.RGB_565;\n    mOptions.inJustDecodeBounds = false;\n    try {\n        \/\/\u533a\u57df\u89e3\u7801\u5668\n        mRegionDecoder = BitmapRegionDecoder.newInstance(is, false);\n    } catch (IOException e) {\n        e.printStackTrace();\n    }\n    requestLayout();\n}<\/code><\/pre>\n<p>\u8bbe\u7f6e\u9700\u8981\u8981\u52a0\u8f7d\u7684\u56fe\u7247\uff0c\u65e0\u8bba\u56fe\u7247\u653e\u5230\u54ea\u91cc\u90fd\u53ef\u4ee5\u62ff\u5230\u56fe\u7247\u7684\u4e00\u4e2a\u8f93\u5165\u6d41\uff0c\u6240\u4ee5\u53c2\u6570\u4f7f\u7528\u8f93\u5165\u6d41\uff0c\u901a\u8fc7<code>BitmapFactory.Options<\/code>\u62ff\u5230\u56fe\u7247\u7684\u771f\u5b9e\u5bbd\u9ad8\u3002<\/p>\n<p><code>inPreferredConfig<\/code>\u8fd9\u4e2a\u53c2\u6570\u9ed8\u8ba4\u662f<code>Bitmap.Config.ARGB_8888<\/code>\uff0c\u8fd9\u91cc\u5c06\u5b83\u6539\u6210<code>Bitmap.Config.RGB_565<\/code>\uff0c\u53bb\u6389\u900f\u660e\u901a\u9053\uff0c\u53ef\u4ee5\u51cf\u5c11\u4e00\u534a\u7684\u5185\u5b58\u4f7f\u7528\u3002\u6700\u540e\u521d\u59cb\u5316\u533a\u57df\u89e3\u7801\u5668<code>BitmapRegionDecoder<\/code>\u3002<\/p>\n<p><code>ARGB_8888<\/code>\u5c31\u662f\u75314\u4e2a8\u4f4d\u7ec4\u6210\u537332\u4f4d\uff0c<code>RGB_565<\/code>\u5c31\u662fR\u4e3a5\u4f4d\uff0cG\u4e3a6\u4f4d\uff0cB\u4e3a5\u4f4d\u517116\u4f4d<\/p>\n<h3>\u83b7\u53d6View\u7684\u5bbd\u9ad8\uff0c\u8ba1\u7b97\u7f29\u653e\u503c<\/h3>\n<pre><code class=\"language-java\">@Override\nprotected void onSizeChanged(int w, int h, int oldw, int oldh) {\n    super.onSizeChanged(w, h, oldw, oldh);\n    mViewWidth = w;\n    mViewHeight = h;\n    mRect.top = 0;\n    mRect.left = 0;\n    mRect.right = (int) mViewWidth;\n    mRect.bottom = (int) mViewHeight;\n    mScale = mViewWidth\/mImageWidth;\n    mCurrentScale = mScale;\n}<\/code><\/pre>\n<p><code>onSizeChanged<\/code>\u65b9\u6cd5\u5728\u5e03\u5c40\u671f\u95f4\uff0c\u5f53\u6b64\u89c6\u56fe\u7684\u5927\u5c0f\u53d1\u751f\u66f4\u6539\u65f6\uff0c\u5c06\u8c03\u7528\u6b64\u65b9\u6cd5\uff0c\u7b2c\u4e00\u6b21\u5728<code>onMeasure<\/code>\u4e4b\u540e\u8c03\u7528\uff0c\u53ef\u4ee5\u65b9\u4fbf\u7684\u62ff\u5230View\u7684\u5bbd\u9ad8\u3002<\/p>\n<p>\u7136\u540e\u7ed9\u6211\u4eec\u81ea\u5b9a\u4e49\u7684\u77e9\u5f62<code>mRect<\/code>\u7684\u4e0a\u4e0b\u5de6\u53f3\u7684\u8fb9\u754c\u8d4b\u503c\u3002\u4e00\u822c\u60c5\u51b5\u4e0b\u6211\u4eec\u4f7f\u7528\u8fd9\u4e2a\u81ea\u5b9a\u4e49\u7684View\u663e\u793a\u5927\u56fe\uff0c\u90fd\u662f\u5360\u6ee1\u8fd9\u4e2aView\uff0c\u6240\u4ee5\u8fd9\u91cc\u77e9\u5f62\u521d\u59cb\u5927\u5c0f\u5c31\u8ba9\u5b83\u8ddfView\u4e00\u6837\u5927\u3002<\/p>\n<p><code>mScale<\/code>\u7528\u6765\u8bb0\u5f55\u539f\u59cb\u7684\u7f29\u653e\u6bd4\uff0c<code>mCurrentScale<\/code>\u7528\u6765\u8bb0\u5f55\u5f53\u524d\u7684\u6240\u65b9\u6bd4\uff0c\u56e0\u4e3a\u6709\u53cc\u51fb\u653e\u5927\u548c\u624b\u52bf\u7f29\u653e\uff0c<code>mCurrentScale<\/code>\u968f\u7740\u624b\u52bf\u53d8\u5316\u3002<\/p>\n<h3>\u7ed8\u5236<\/h3>\n<pre><code class=\"language-java\">  @Override\n  protected void onDraw(Canvas canvas) {\n      super.onDraw(canvas);\n      if (mRegionDecoder == null) {\n          return;\n      }\n      \/\/\u590d\u7528\u5185\u5b58\n      mOptions.inBitmap = mBitmap;\n      mBitmap = mRegionDecoder.decodeRegion(mRect, mOptions);\n      mMatrix.setScale(mCurrentScale, mCurrentScale);\n      canvas.drawBitmap(mBitmap, mMatrix, null);\n  }<\/code><\/pre>\n<p>\u7ed8\u5236\u4e5f\u5f88\u7b80\u5355\uff0c\u901a\u8fc7\u533a\u57df\u89e3\u7801\u5668\u89e3\u7801\u4e00\u4e2a\u77e9\u5f62\u7684\u533a\u57df\uff0c\u8fd4\u56de\u4e00\u4e2a<code>Bitmap<\/code>\u5bf9\u8c61\uff0c\u7136\u540e\u901a\u8fc7<code>canvas<\/code>\u7ed8\u5236<code>Bitmap<\/code>\u3002\u9700\u8981\u6ce8\u610f<code>mOptions.inBitmap = mBitmap;<\/code>\u8fd9\u4e2a\u914d\u7f6e\u53ef\u4ee5\u590d\u7528\u5185\u5b58\uff0c\u4fdd\u8bc1\u5185\u5b58\u7684\u4f7f\u7528\u4e00\u76f4\u53ea\u662f\u77e9\u5f62\u7684\u8fd9\u5757\u533a\u57df\u3002<\/p>\n<p>\u5230\u8fd9\u91cc\u8fd0\u884c\u5c31\u80fd\u7ed8\u5236\u51fa\u4e00\u90e8\u5206\u56fe\u7247\u4e86\uff0c\u60f3\u8981\u770b\u5168\u90e8\u7684\u56fe\u7247\uff0c\u9700\u8981\u624b\u6307\u62d6\u52a8\u6765\u770b\uff0c\u8fd9\u5c31\u9700\u8981\u5904\u7406\u5404\u79cd\u4e8b\u4ef6\u4e86\u3002<\/p>\n<h3>\u5206\u53d1\u4e8b\u4ef6<\/h3>\n<pre><code class=\"language-java\">@Override\npublic boolean onTouchEvent(MotionEvent event) {\n    mGestureDetector.onTouchEvent(event);\n\n    mScaleGestureDetector.onTouchEvent(event);\n    return true;\n}\n\n`onTouchEvent`\u4e2d\u5f88\u7b80\u5355\uff0c\u4e8b\u4ef6\u90fd\u4ea4\u7ed9\u4e24\u4e2a\u624b\u52bf\u68c0\u6d4b\u5668\u81ea\u5df1\u53bb\u5904\u7406\u3002\n\n### \u5904\u7406GestureDetector\u4e2d\u7684\u4e8b\u4ef6\n\n\u5f53\u624b\u6307\u6309\u4e0b\u7684\u65f6\u5019\uff0c\u5982\u679c\u56fe\u7247\u6b63\u5728\u98de\u901f\u6ed1\u52a8\uff0c\u90a3\u4e48\u505c\u6b62\n\n```java\n@Override\npublic boolean onDown(MotionEvent e) {\n    \/\/\u5982\u679c\u6b63\u5728\u6ed1\u52a8\uff0c\u5148\u505c\u6b62\n    if (!mScroller.isFinished()) {\n        mScroller.forceFinished(true);\n    }\n    return true;\n}<\/code><\/pre>\n<p>`onScroll`\u4e2d\u5904\u7406\u6ed1\uff0c\u6839\u636e\u624b\u6307\u79fb\u52a8\u7684\u53c2\u6570\uff0c\u6765\u79fb\u52a8\u77e9\u5f62\u7ed8\u5236\u533a\u57df\uff0c\u8fd9\u91cc\u9700\u8981\u5904\u7406\u5404\u4e2a\u8fb9\u754c\u70b9\uff0c\u6bd4\u5982\u5de6\u8fb9\u6700\u5c0f\u5c31\u4e3a0\uff0c\u53f3\u8fb9\u6700\u5927\u4e3a\u56fe\u7247\u7684\u5bbd\u5ea6\uff0c\u4e0d\u80fd\u8d85\u51fa\u8fb9\u754c\u5426\u5219\u5c31\u62a5\u9519\u4e86\u3002<\/p>\n<p>\u5728`onFling`\u65b9\u6cd5\u4e2d\u8c03\u7528\u6ed1\u52a8\u5668`Scroller`\u7684`fling`\u65b9\u6cd5\u6765\u5904\u7406\u624b\u6307\u79bb\u5f00\u4e4b\u540e\u60ef\u6027\u6ed1\u52a8\u3002\u60ef\u6027\u79fb\u52a8\u7684\u8ddd\u79bb\u5728View\u7684`computeScroll()`\u65b9\u6cd5\u4e2d\u8ba1\u7b97\uff0c\u4e5f\u9700\u8981\u6ce8\u610f\u8fb9\u754c\u95ee\u9898\uff0c\u4e0d\u8981\u6ed1\u51fa\u8fb9\u754c\u3002<\/p>\n<pre><code class=\"language-java\">@Override\npublic boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {\n    \/\/\u6ed1\u52a8\u7684\u65f6\u5019\uff0c\u6539\u53d8mRect\u663e\u793a\u533a\u57df\u7684\u4f4d\u7f6e\n    mRect.offset((int)distanceX,(int)distanceY);\n    \/\/\u5904\u7406\u4e0a\u4e0b\u5de6\u53f3\u7684\u8fb9\u754c\n    if (mRect.left < 0) {\n        mRect.left = 0;\n        mRect.right = (int) (mViewWidth\/mCurrentScale);\n    }\n    if (mRect.right > mImageWidth) {\n        mRect.right = (int) mImageWidth;\n        mRect.left = (int) (mImageWidth-mViewWidth\/mCurrentScale);\n    }\n    if (mRect.top < 0) {\n        mRect.top = 0;\n        mRect.bottom = (int) (mViewHeight\/mCurrentScale);\n    }\n    if (mRect.bottom > mImageHeight) {\n        mRect.bottom = (int) mImageHeight;\n        mRect.top = (int) (mImageHeight-mViewHeight\/mCurrentScale);\n    }\n    invalidate();\n    return false;\n}\n\n@Override\npublic boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {\n    mScroller.fling(mRect.left, mRect.top, -(int)velocityX, -(int)velocityY, 0, (int)mImageWidth\n            , 0, (int)mImageHeight);\n    return false;\n}\n\n@Override\npublic void computeScroll() {\n    super.computeScroll();\n    if (!mScroller.isFinished() && mScroller.computeScrollOffset()) {\n        if (mRect.top+mViewHeight\/mCurrentScale < mImageHeight) {\n            mRect.top = mScroller.getCurrY();\n            mRect.bottom = (int) (mRect.top + mViewHeight\/mCurrentScale);\n        }\n        if (mRect.bottom > mImageHeight) {\n            mRect.top = (int) (mImageHeight - mViewHeight\/mCurrentScale);\n            mRect.bottom = (int) mImageHeight;\n        }\n        invalidate();\n    }\n}<\/code><\/pre>\n<h3>\u5904\u7406\u53cc\u51fb\u4e8b\u4ef6<\/h3>\n<pre><code class=\"language-java\">@Override\npublic boolean onDoubleTap(MotionEvent e) {\n    \/\/\u5904\u7406\u53cc\u51fb\u4e8b\u4ef6\n    if (mCurrentScale > mScale) {\n        mCurrentScale = mScale;\n    } else {\n        mCurrentScale = mScale*mMultiple;\n    }\n    mRect.right = mRect.left + (int)(mViewWidth\/mCurrentScale);\n    mRect.bottom = mRect.top + (int)(mViewHeight\/mCurrentScale);\n    \/\/\u5904\u7406\u8fb9\u754c\n    if (mRect.left < 0) {\n        mRect.left = 0;\n        mRect.right = (int) (mViewWidth\/mCurrentScale);\n    }\n    if (mRect.right > mImageWidth) {\n        mRect.right = (int) mImageWidth;\n        mRect.left = (int) (mImageWidth-mViewWidth\/mCurrentScale);\n    }\n    if (mRect.top < 0) {\n        mRect.top = 0;\n        mRect.bottom = (int) (mViewHeight\/mCurrentScale);\n    }\n    if (mRect.bottom > mImageHeight) {\n        mRect.bottom = (int) mImageHeight;\n        mRect.top = (int) (mImageHeight-mViewHeight\/mCurrentScale);\n    }\n\n    invalidate();\n    return true;\n}<\/code><\/pre>\n<p>mMultiple\u4e3a\u53cc\u51fb\u4e4b\u540e\u653e\u5927\u51e0\u500d\uff0c\u8fd9\u91cc\u8bbe\u7f6e3\u500d\u3002\u7b2c\u4e00\u6b21\u53cc\u51fb\u653e\u59273\u500d\uff0c\u7b2c\u4e8c\u6b21\u53cc\u51fb\u8fd4\u56de\u539f\u72b6\u3002\u7f29\u653e\u5b8c\u6210\u4e4b\u540e\uff0c\u9700\u8981\u6839\u636e\u5f53\u524d\u7684\u7f29\u653e\u6bd4\u91cd\u65b0\u8bbe\u7f6e\u7ed8\u5236\u533a\u57df\u7684\u8fb9\u754c\u3002\u6700\u540e\u4e5f\u9700\u8981\u91cd\u65b0\u5b9a\u4f4d\u4e00\u4e0b\u8fb9\u754c\uff0c\u56e0\u4e3a\u5982\u679c\u4f7f\u7528\u4e24\u4e2a\u624b\u6307\u653e\u5927\u4e4b\u540e\uff0c\u8fd9\u65f6\u5019\u53cc\u51fb\u8fd4\u56de\u539f\u72b6\uff0c\u5982\u679c\u4e0d\u5904\u7406\u8fb9\u754c\uff0c\u4f4d\u7f6e\u4f1a\u51fa\u9519\u3002\u5904\u7406\u8fb9\u754c\u7684\u4ee3\u7801\u53ef\u4ee5\u62bd\u53d6\u51fa\u6765\u3002<\/p>\n<h3>\u5904\u7406\u624b\u6307\u7f29\u653e\u4e8b\u4ef6<\/h3>\n<pre><code class=\"language-java\">@Override\npublic boolean onScale(ScaleGestureDetector detector) {\n    \/\/\u5904\u7406\u624b\u6307\u7f29\u653e\u4e8b\u4ef6\n    \/\/\u83b7\u53d6\u4e0e\u4e0a\u6b21\u4e8b\u4ef6\u76f8\u6bd4\uff0c\u5f97\u5230\u7684\u6bd4\u4f8b\u56e0\u5b50\n    float scaleFactor = detector.getScaleFactor();\n    \/\/mCurrentScale += scaleFactor-1;\n    mCurrentScale *= scaleFactor;\n    if (mCurrentScale > mScale*mMultiple) {\n        mCurrentScale = mScale*mMultiple;\n    } else if (mCurrentScale <= mScale) {\n        mCurrentScale = mScale;\n    }\n    mRect.right = mRect.left + (int)(mViewWidth\/mCurrentScale);\n    mRect.bottom = mRect.top + (int)(mViewHeight\/mCurrentScale);\n    invalidate();\n    return true;\n}\n\n@Override\npublic boolean onScaleBegin(ScaleGestureDetector detector) {\n    \/\/\u5f53 >= 2 \u4e2a\u624b\u6307\u78b0\u89e6\u5c4f\u5e55\u65f6\u8c03\u7528\uff0c\u82e5\u8fd4\u56de false \u5219\u5ffd\u7565\u6539\u4e8b\u4ef6\u8c03\u7528\n    return true;\n}<\/code><\/pre>\n<p>`onScaleBegin`\u65b9\u6cd5\u9700\u8981\u8fd4\u56detrue\uff0c\u5426\u5219\u65e0\u6cd5\u68c0\u6d4b\u5230\u624b\u52bf\u7f29\u653e\u3002`onScale`\u65b9\u6cd5\u4e2d\u83b7\u53d6\u7f29\u653e\u56e0\u5b50\uff0c\u8fd9\u4e2a\u7f29\u653e\u56e0\u5b50\u662f\u8ddf\u4e0a\u6b21\u4e8b\u4ef6\u76f8\u6bd4\u7684\u51fa\u6765\u7684\u3002\u6240\u4ee5\u8fd9\u91cc\u4f7f\u7528`*=`\uff0c\u5b8c\u6210\u4e4b\u540e\u4e5f\u9700\u8981\u91cd\u65b0\u8bbe\u7f6e\u7ed8\u5236\u533a\u57df`mRect`\u7684\u8fb9\u754c\u3002<\/p>\n<h2>\u6e90\u7801<\/h2>\n<pre><code class=\"language-java\">import android.content.Context;\nimport android.graphics.Bitmap;\nimport android.graphics.BitmapFactory;\nimport android.graphics.BitmapRegionDecoder;\nimport android.graphics.Canvas;\nimport android.graphics.Matrix;\nimport android.graphics.Rect;\nimport android.util.AttributeSet;\nimport android.view.GestureDetector;\nimport android.view.MotionEvent;\nimport android.view.ScaleGestureDetector;\nimport android.view.View;\nimport android.widget.Scroller;\n\nimport androidx.annotation.Nullable;\n\nimport java.io.IOException;\nimport java.io.InputStream;\n\n\/**\n * \u52a0\u8f7d\u5927\u56fe\n *\/\npublic class BigImageView extends View implements GestureDetector.OnGestureListener, GestureDetector.OnDoubleTapListener,\n        ScaleGestureDetector.OnScaleGestureListener {\n\n    \/**\n     * \u56fe\u7247\u7684\u5bbd\u548c\u9ad8\n     *\/\n    private float mImageWidth, mImageHeight;\n    \/**\n     * \u5f53\u524dView\u7684\u5bbd\u548c\u9ad8\n     *\/\n    private float mViewWidth, mViewHeight;\n    \/**\n     * \u56fe\u7247\u7684\u7f29\u653e\u6bd4\n     *\/\n    private float mScale = 1;\n    private float mCurrentScale = 1;\n    \/**\n     * \u653e\u5927\u51e0\u500d\n     *\/\n    private int mMultiple = 3;\n    \/**\n     * \u7ed8\u5236\u533a\u57df\n     *\/\n    private final Rect mRect = new Rect();\n    \/**\n     * \u5206\u533a\u57df\u52a0\u8f7d\u5668\n     *\/\n    private BitmapRegionDecoder mRegionDecoder;\n    private BitmapFactory.Options mOptions;\n    private Bitmap mBitmap;\n    \/**\n     * \u6ed1\u52a8\u5668\n     *\/\n    private Scroller mScroller;\n    \/**\n     * \u7f29\u653e\u77e9\u9635\n     *\/\n    private Matrix mMatrix;\n    \/**\n     * \u624b\u52bf\u8bc6\u522b\u5668\n     *\/\n    private GestureDetector mGestureDetector;\n    private ScaleGestureDetector mScaleGestureDetector;\n\n    public BigImageView(Context context) {\n        super(context);\n        init();\n    }\n\n    public BigImageView(Context context, @Nullable AttributeSet attrs) {\n        super(context, attrs);\n        init();\n    }\n\n    public BigImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {\n        super(context, attrs, defStyleAttr);\n        init();\n    }\n\n    private void init() {\n        mOptions = new BitmapFactory.Options();\n        \/\/\u6ed1\u52a8\u5668\n        mScroller = new Scroller(getContext());\n        \/\/\u6240\u653e\u5668\n        mMatrix = new Matrix();\n        \/\/\u624b\u52bf\u8bc6\u522b\n        mGestureDetector = new GestureDetector(getContext(), this);\n        mScaleGestureDetector = new ScaleGestureDetector(getContext(), this);\n    }\n\n    public void setImage(InputStream is) {\n        mOptions.inJustDecodeBounds = true;\n        BitmapFactory.decodeStream(is, null, mOptions);\n        mImageWidth = mOptions.outWidth;\n        mImageHeight = mOptions.outHeight;\n        mOptions.inPreferredConfig = Bitmap.Config.RGB_565;\n        mOptions.inJustDecodeBounds = false;\n        try {\n            \/\/\u533a\u57df\u89e3\u7801\u5668\n            mRegionDecoder = BitmapRegionDecoder.newInstance(is, false);\n        } catch (IOException e) {\n            e.printStackTrace();\n        }\n        requestLayout();\n    }\n\n    @Override\n    protected void onSizeChanged(int w, int h, int oldw, int oldh) {\n        super.onSizeChanged(w, h, oldw, oldh);\n        mViewWidth = w;\n        mViewHeight = h;\n        mRect.top = 0;\n        mRect.left = 0;\n        mRect.right = (int) mViewWidth;\n        mRect.bottom = (int) mViewHeight;\n        mScale = mViewWidth \/ mImageWidth;\n        mCurrentScale = mScale;\n    }\n\n    @Override\n    protected void onDraw(Canvas canvas) {\n        super.onDraw(canvas);\n        if (mRegionDecoder == null) {\n            return;\n        }\n        \/\/\u590d\u7528\u5185\u5b58\n        mOptions.inBitmap = mBitmap;\n        mBitmap = mRegionDecoder.decodeRegion(mRect, mOptions);\n        mMatrix.setScale(mCurrentScale, mCurrentScale);\n        canvas.drawBitmap(mBitmap, mMatrix, null);\n    }\n\n    @Override\n    public boolean onTouchEvent(MotionEvent event) {\n        mGestureDetector.onTouchEvent(event);\n\n        mScaleGestureDetector.onTouchEvent(event);\n        return true;\n    }\n\n    @Override\n    public boolean onDown(MotionEvent e) {\n        \/\/\u5982\u679c\u6b63\u5728\u6ed1\u52a8\uff0c\u5148\u505c\u6b62\n        if (!mScroller.isFinished()) {\n            mScroller.forceFinished(true);\n        }\n        return true;\n    }\n\n    @Override\n    public void onShowPress(MotionEvent e) {\n\n    }\n\n    @Override\n    public boolean onSingleTapUp(MotionEvent e) {\n        return false;\n    }\n\n    @Override\n    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {\n        \/\/\u6ed1\u52a8\u7684\u65f6\u5019\uff0c\u6539\u53d8mRect\u663e\u793a\u533a\u57df\u7684\u4f4d\u7f6e\n        mRect.offset((int) distanceX, (int) distanceY);\n        \/\/\u5904\u7406\u4e0a\u4e0b\u5de6\u53f3\u7684\u8fb9\u754c\n        handleBorder();\n        invalidate();\n        return false;\n    }\n\n    private void handleBorder() {\n        if (mRect.left < 0) {\n            mRect.left = 0;\n            mRect.right = (int) (mViewWidth \/ mCurrentScale);\n        }\n        if (mRect.right > mImageWidth) {\n            mRect.right = (int) mImageWidth;\n            mRect.left = (int) (mImageWidth - mViewWidth \/ mCurrentScale);\n        }\n        if (mRect.top < 0) {\n            mRect.top = 0;\n            mRect.bottom = (int) (mViewHeight \/ mCurrentScale);\n        }\n        if (mRect.bottom > mImageHeight) {\n            mRect.bottom = (int) mImageHeight;\n            mRect.top = (int) (mImageHeight - mViewHeight \/ mCurrentScale);\n        }\n    }\n\n    @Override\n    public void onLongPress(MotionEvent e) {\n\n    }\n\n    @Override\n    public void computeScroll() {\n        super.computeScroll();\n        if (!mScroller.isFinished() && mScroller.computeScrollOffset()) {\n            if (mRect.top + mViewHeight \/ mCurrentScale < mImageHeight) {\n                mRect.top = mScroller.getCurrY();\n                mRect.bottom = (int) (mRect.top + mViewHeight \/ mCurrentScale);\n            }\n            if (mRect.bottom > mImageHeight) {\n                mRect.top = (int) (mImageHeight - mViewHeight \/ mCurrentScale);\n                mRect.bottom = (int) mImageHeight;\n            }\n            invalidate();\n        }\n    }\n\n    @Override\n    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {\n        mScroller.fling(mRect.left, mRect.top, -(int) velocityX, -(int) velocityY, 0, (int) mImageWidth\n                , 0, (int) mImageHeight);\n        return false;\n    }\n\n    @Override\n    public boolean onSingleTapConfirmed(MotionEvent e) {\n        return false;\n    }\n\n    @Override\n    public boolean onDoubleTap(MotionEvent e) {\n        \/\/\u5904\u7406\u53cc\u51fb\u4e8b\u4ef6\n        if (mCurrentScale > mScale) {\n            mCurrentScale = mScale;\n        } else {\n            mCurrentScale = mScale * mMultiple;\n        }\n        mRect.right = mRect.left + (int) (mViewWidth \/ mCurrentScale);\n        mRect.bottom = mRect.top + (int) (mViewHeight \/ mCurrentScale);\n        \/\/\u5904\u7406\u4e0a\u4e0b\u5de6\u53f3\u7684\u8fb9\u754c\n        handleBorder();\n        invalidate();\n        return true;\n    }\n\n    @Override\n    public boolean onDoubleTapEvent(MotionEvent e) {\n        return false;\n    }\n\n    @Override\n    public boolean onScale(ScaleGestureDetector detector) {\n        \/\/\u5904\u7406\u624b\u6307\u7f29\u653e\u4e8b\u4ef6\n        \/\/\u83b7\u53d6\u4e0e\u4e0a\u6b21\u4e8b\u4ef6\u76f8\u6bd4\uff0c\u5f97\u5230\u7684\u6bd4\u4f8b\u56e0\u5b50\n        float scaleFactor = detector.getScaleFactor();\n\/\/        mCurrentScale+=scaleFactor-1;\n        mCurrentScale *= scaleFactor;\n        if (mCurrentScale > mScale * mMultiple) {\n            mCurrentScale = mScale * mMultiple;\n        } else if (mCurrentScale <= mScale) {\n            mCurrentScale = mScale;\n        }\n        mRect.right = mRect.left + (int) (mViewWidth \/ mCurrentScale);\n        mRect.bottom = mRect.top + (int) (mViewHeight \/ mCurrentScale);\n        invalidate();\n        return true;\n    }\n\n    @Override\n    public boolean onScaleBegin(ScaleGestureDetector detector) {\n        \/\/\u5f53 >= 2 \u4e2a\u624b\u6307\u78b0\u89e6\u5c4f\u5e55\u65f6\u8c03\u7528\uff0c\u82e5\u8fd4\u56de false \u5219\u5ffd\u7565\u6539\u4e8b\u4ef6\u8c03\u7528\n        return true;\n    }\n\n    @Override\n    public void onScaleEnd(ScaleGestureDetector detector) {\n\n    }\n}<\/code><\/pre>\n<p>\u672c\u6587\u8f6c\u8f7d\u81f3\uff1a<a target=\"_blank\" rel=\"noopener\" href=\"https:\/\/www.jianshu.com\/p\/ca4e086a8b1d\">https:\/\/www.jianshu.com\/p\/ca4e086a8b1d<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u9762\u8bd5\u9898 \u56fe\u7247\u7684\u4e09\u7ea7\u7f13\u5b58\u4e2d\uff0c\u56fe\u7247\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\uff0c\u5982\u679c\u5185\u5b58\u5feb\u7206\u4e86\uff0c\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1f\u600e\u4e48\u5904\u7406\uff1f \u5185\u5b58\u4e2d\u5982\u679c\u52a0\u8f7d\u4e00\u5f20 500 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[311],"tags":[511,256],"class_list":["post-2008","post","type-post","status-publish","format-standard","hentry","category-android-advance","tag-bitmap","tag-oom"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/2008","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=2008"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/2008\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=2008"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=2008"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=2008"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}