Android放大镜效果实现
iyjk0240
8年前
<h2>概述</h2> <p>我相信很多用过英语应用的同学都看多一个放大镜的效果,就是选中一段文字后,会有一个放大镜,这个究竟怎么实现的呢,我们今天来分析分析。</p> <p><img src="https://simg.open-open.com/show/acf7fdb11cced85489cf4ed5d5c8b1b8.jpg"></p> <p>源码分析</p> <pre> <code class="language-java">public class ShaderView extends View { private final Bitmap bitmap; private final ShapeDrawable drawable; // 放大镜的半径 private static final int RADIUS = 80; // 放大倍数 private static final int FACTOR = 3; private final Matrix matrix = new Matrix(); public ShaderView(Context context) { super(context); Bitmap bmp = BitmapFactory.decodeResource(getResources(),R.drawable.demo); bitmap = bmp; BitmapShader shader = new BitmapShader(Bitmap.createScaledBitmap(bmp, bmp.getWidth() * FACTOR, bmp.getHeight() * FACTOR, true), TileMode.CLAMP, TileMode.CLAMP); // 圆形的drawable drawable = new ShapeDrawable(new OvalShape()); drawable.getPaint().setShader(shader); drawable.setBounds(0, 0, RADIUS * 2, RADIUS * 2); } @Override public boolean onTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); // 这个位置表示的是,画shader的起始位置 matrix.setTranslate(RADIUS - x * FACTOR, RADIUS - y * FACTOR); drawable.getPaint().getShader().setLocalMatrix(matrix); // bounds,就是那个圆的外切矩形 drawable.setBounds(x - RADIUS, y - RADIUS, x + RADIUS, y + RADIUS); invalidate(); return true; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawBitmap(bitmap, 0, 0, null); drawable.draw(canvas); } } </code></pre> <p>基本原理就是使用ShapeDrawable构造一个圆形的drawable,然后它的paint的shader设置为将要放大的图片,然后就是简单的位置移动问题了。放大镜的半径和放大倍数都可以在代码里面修改,代码都有注释,应该很好理解了。</p> <p>不过,一个问题如果只有一种解决方法的话,那未免有点令人沮丧,想玩点另类的都不行。玩程序就得玩出个性,玩出激情。哈哈,废话太多,切回正题。再来看看放大镜的另外一种实现吧</p> <pre> <code class="language-java">public class PathView extends View { private final Path mPath = new Path(); private final Matrix matrix = new Matrix(); private final Bitmap bitmap; // 放大镜的半径 private static final int RADIUS = 80; // 放大倍数 private static final int FACTOR = 2; private int mCurrentX, mCurrentY; public PathView(Context context) { super(context); mPath.addCircle(RADIUS, RADIUS, RADIUS, Direction.CW); matrix.setScale(FACTOR, FACTOR); bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.demo); } @Override public boolean onTouchEvent(MotionEvent event) { mCurrentX = (int) event.getX(); mCurrentY = (int) event.getY(); invalidate(); return true; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); // 底图 canvas.drawBitmap(bitmap, 0, 0, null); // 剪切 canvas.translate(mCurrentX - RADIUS, mCurrentY - RADIUS); canvas.clipPath(mPath); // 画放大后的图 canvas.translate(RADIUS - mCurrentX * FACTOR, RADIUS - mCurrentY * FACTOR); canvas.drawBitmap(bitmap, matrix, null); } } </code></pre> <p>这里使用的是Path类,将canvas剪切出一块圆形区域,在其上绘制放大的部分。</p> <p>工程下载地址http://download.csdn.net/detail/hustpzb/4523274</p> <p> </p> <p>来自:http://mobile.51cto.com/android-529109.htm</p> <p> </p>