Android自定义ImageView实现自动放大缩小动画

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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。