這篇講的是如何生成一個自定義的ImageView，實現自動放大縮小動畫。
為什么實現這個功能呢？因為我想在ViewPager實現圖片放大縮小的動畫，但是ViewPager幾個頁面的動畫會一起動，而且放大全屏圖片的話會相互覆蓋，很詭異。于是上網搜demo，一無所獲。迫于無奈。。。
廢話不多說，直接貼代碼。
1.配置文件直接添加
當直接在布局文件中添加圖片的話，可以在自定義View代碼中用getDrawable（）獲取圖片資源，然后通過DrawBitmap繪制圖片。通過不斷繪制圖片的位置，達到放大縮小的功能。
第一種情況實在XML布局文件中直接添加的：
public class CoolImageView extends ImageView { private int mLeft = 0; private int mTop = 0; private Handler mHandler; private Bitmap bitmap; private Rect srcRect = new Rect(); private Rect dstRect = new Rect(); private int imgWidth; private int imgHeight; private boolean flag; private boolean istart; public CoolImageView(Context context) { super(context); } public CoolImageView(Context context, AttributeSet attrs) { super(context, attrs); setUp(context, attrs); } public CoolImageView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); setUp(context, attrs); } private void setUp(Context context, AttributeSet attrs) { mHandler = new MoveHandler(); mHandler.sendEmptyMessageDelayed(1, 220L); istart = true; } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); int width = getWidth(); int height = getHeight(); //獲取圖片資源 BitmapDrawable drawable = (BitmapDrawable) getDrawable(); bitmap = drawable.getBitmap(); dstRect.left = 0; dstRect.top = 0; dstRect.right = width; dstRect.bottom = height; if (bitmap != null) { if (istart) {// 獲取圖片的寬高 imgWidth = bitmap.getWidth(); imgHeight = bitmap.getHeight(); srcRect.left = 0 + mLeft; srcRect.right = imgWidth - mLeft; srcRect.top = 0 + mTop; srcRect.bottom = imgHeight - mTop; canvas.drawBitmap(bitmap, srcRect, dstRect, null); } else { canvas.drawBitmap(bitmap, null, dstRect, null); } } } private class MoveHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case 1: if (imgHeight != 0) { if (mTop == 0) { mTop += 5; mLeft += 5; } else if (mTop == 120) { mTop -= 5; mLeft -= 5; } } postInvalidate(); mHandler.sendEmptyMessageDelayed(1, 250); break; } } } public void start() { mTop = 0; mLeft = 0; istart = true; mHandler.sendEmptyMessageDelayed(1, 220L); } public void stop() { istart = false; }}2 .通過Glide加載圖片的方式
通過Glide加載圖片的話，不能直接用getDrawable獲取圖片資源。Glide加載圖片的方式也需要改變。廢話不多說，直接上代碼。
CoolimageView直接從Glide的緩存中加載圖片。
Glide.with(GoodsPagerActivity.this) .load(sList.get(position).img) .override(width, height) .centerCrop() .into(new SimpleTarget<GlideDrawable>() { @Override public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> glideAnimation) { imageView.setImageDrawable(resource); } });CoolImageView.java:
唯一不同的是獲取圖片的方式；
```java
public class CoolImageView extends ImageView { private int mLeft = 0; private int mTop = 0; private Handler mHandler; private Bitmap bitmap; private Rect srcRect = new Rect(); private Rect dstRect = new Rect(); private int imgWidth; private int imgHeight; private boolean flag; private boolean istart; private int width; private int height; public CoolImageView(Context context) { super(context); } public CoolImageView(Context context, AttributeSet attrs) { super(context, attrs); setUp(context, attrs); } public CoolImageView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); setUp(context, attrs); } private void setUp(Context context, AttributeSet attrs) { mHandler = new MoveHandler(); mHandler.sendEmptyMessageDelayed(1, 220L); istart = true; } @Override public void setImageDrawable(@Nullable Drawable drawable) { super.setImageDrawable(drawable); if (mHandler != null) { mHandler.sendEmptyMessageDelayed(1, 220L); } else { mHandler = new MoveHandler(); mHandler.sendEmptyMessageDelayed(1, 220L); istart = true; } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); width = getWidth(); height = getHeight(); GlideBitmapDrawable drawable = (GlideBitmapDrawable) getDrawable(); if (drawable != null) { bitmap = drawable.getBitmap(); } dstRect.left = 0; dstRect.top = 0; dstRect.right = width; dstRect.bottom = height; if (bitmap != null) { if (istart) { imgWidth = bitmap.getWidth(); imgHeight = bitmap.getHeight(); srcRect.left = 0 + mLeft; srcRect.right = imgWidth - mLeft; srcRect.top = 0 + mTop; srcRect.bottom = imgHeight - mTop; canvas.drawBitmap(bitmap, srcRect, dstRect, null); } else { canvas.drawBitmap(bitmap, null, dstRect, null); } } } private class MoveHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case 1: if (imgHeight != 0) { if (mTop == 0) { flag = true; } else if (mTop == 60) { flag = false; } if (!flag) { mTop -= 2; mLeft -= 1; } else { mTop += 2; mLeft += 1; } } postInvalidate(); mHandler.sendEmptyMessageDelayed(1, 200); break; } } } public void start() { mTop = 0; mLeft = 0; istart = true; mHandler.sendEmptyMessageDelayed(1, 220L); } public void stop() { istart = false; }}如果感覺動畫不夠流暢可以縮小線程等待時間。
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