Android自定义ImageView实现自动放大缩小动画

2019-12-12 02:40:12

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这篇讲的是如何生成一个自定义的ImageView，实现自动放大缩小动画。

为什么实现这个功能呢？因为我想在ViewPager实现图片放大缩小的动画，但是ViewPager几个页面的动画会一起动，而且放大全屏图片的话会相互覆盖，很诡异。于是上网搜demo，一无所获。迫于无奈。。。
废话不多说，直接贴代码。

1.配置文件直接添加

当直接在布局文件中添加图片的话，可以在自定义View代码中用getDrawable（）获取图片资源，然后通过DrawBitmap绘制图片。通过不断绘制图片的位置，达到放大缩小的功能。
第一种情况实在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();    //获取图片资源    BitmapDrawable drawable = (BitmapDrawable) getDrawable();    bitmap = drawable.getBitmap();    dstRect.left = 0;    dstRect.top = 0;    dstRect.right = width;    dstRect.bottom = height;    if (bitmap != null) {      if (istart) {//        获取图片的宽高        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 .通过Glide加载图片的方式

通过Glide加载图片的话，不能直接用getDrawable获取图片资源。Glide加载图片的方式也需要改变。废话不多说，直接上代码。
CoolimageView直接从Glide的缓存中加载图片。

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:
唯一不同的是获取图片的方式；
```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;  }}

如果感觉动画不够流畅可以缩小线程等待时间。

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