Android编程滑动效果之倒影效果实现方法(附demo源码下载)

本文实例讲述了Android编程滑动效果之倒影效果实现方法。分享给大家供大家参考，具体如下：

前面介绍了使用《Android编程实现3D滑动旋转效果的方法》，现在介绍图片倒影实现，先看效果图

这里主要通过自定义Gallery和ImageAdapter（继承自BaseAdapter）实现

1、倒影绘制

ImageAdapter继承自BaseAdapter，详细实现可见前面关于Android Gallery的用法。这里重点介绍倒影原理及实现

倒影原理：

倒影效果是主要由原图+间距+倒影三部分组成，高度大约为原图的3/2（原图为1、倒影为1/2）
原图，就是我们看到了最开始的图片
间距，是原图与倒影之间的间隙，如：reflectionGap = 4;
倒影，是原图下半部分1/2高度，通过矩阵变换matrix.preScale(1, -1); 获取倒立图片，然后再加上线性遮罩和阴影实现

倒影实现：

/** 反射倒影 */
public boolean createReflectedImages() {
  final int reflectionGap = 4;
  int index = 0;
  for (Map<String, Object> map : list) {
    Integer id = (Integer) map.get("image");
    Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), id); // 获取原始图片
    int width = originalImage.getWidth();
    int height = originalImage.getHeight();
    Matrix matrix = new Matrix();
    matrix.preScale(1, -1); // 图片矩阵变换（从低部向顶部的倒影）
    Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false); // 截取原图下半部分
    Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888); // 创建倒影图片（高度为原图3/2）
    Canvas canvas = new Canvas(bitmapWithReflection); // 绘制倒影图（原图 + 间距 + 倒影）
    canvas.drawBitmap(originalImage, 0, 0, null); // 绘制原图
    Paint paint = new Paint();
    canvas.drawRect(0, height, width, height + reflectionGap, paint); // 绘制原图与倒影的间距
    canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null); // 绘制倒影图
    paint = new Paint();
    LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
    paint.setShader(shader); // 线性渐变效果
    paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); // 倒影遮罩效果
    canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint); // 绘制倒影的阴影效果
    ImageView imageView = new ImageView(mContext);
    imageView.setImageBitmap(bitmapWithReflection); // 设置倒影图片
    imageView.setLayoutParams(new myGallery.LayoutParams(180, 240));
    imageView.setScaleType(ScaleType.MATRIX);
    mImages[index++] = imageView;
  }
  return true;
}

2、myGallery

自定义Gallery来实现倒影图片的浏览与选择

public class myGallery extends Gallery {
  private Camera mCamera = new Camera();
  private int mMaxRotationAngle = 60; // 最大旋转角度 60
  private int mMaxZoom = -120;
  private int mCoveflowCenter;
  public myGallery(Context context) {
    super(context);
    this.setStaticTransformationsEnabled(true);
  }
  public myGallery(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.setStaticTransformationsEnabled(true);
  }
  public myGallery(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    this.setStaticTransformationsEnabled(true);
  }
  public int getMaxRotationAngle() {
    return mMaxRotationAngle;
  }
  public void setMaxRotationAngle(int maxRotationAngle) {
    mMaxRotationAngle = maxRotationAngle;
  }
  public int getMaxZoom() {
    return mMaxZoom;
  }
  public void setMaxZoom(int maxZoom) {
    mMaxZoom = maxZoom;
  }
  /** 获取Gallery的中心x */
  private int getCenterOfCoverflow() {
    return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
  }
  /** 获取View的中心x */
  private static int getCenterOfView(View view) {
    return view.getLeft() + view.getWidth() / 2;
  }
  @Override
  protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    mCoveflowCenter = getCenterOfCoverflow();
    super.onSizeChanged(w, h, oldw, oldh);
  }
  @Override
  protected boolean getChildStaticTransformation(View child, Transformation trans) {
    final int childCenter = getCenterOfView(child);
    final int childWidth = child.getWidth();
    int rotationAngle = 0;
    trans.clear();
    trans.setTransformationType(Transformation.TYPE_BOTH); // alpha 和 matrix 都变换
    if (childCenter == mCoveflowCenter) { // 正中间的childView
      transformImageBitmap((ImageView) child, trans, 0);
    } else { // 两侧的childView
      rotationAngle = (int) ( ( (float) (mCoveflowCenter - childCenter) / childWidth ) * mMaxRotationAngle );
      if (Math.abs(rotationAngle) > mMaxRotationAngle) {
        rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
      }
      transformImageBitmap((ImageView) child, trans, rotationAngle);
    }
    return true;
  }
  private void transformImageBitmap(ImageView child, Transformation trans, int rotationAngle) {
    mCamera.save();
    final Matrix imageMatrix = trans.getMatrix();
    final int imageHeight = child.getLayoutParams().height;
    final int imageWidth = child.getLayoutParams().width;
    final int rotation = Math.abs(rotationAngle);
    // 在Z轴上正向移动camera的视角，实际效果为放大图片; 如果在Y轴上移动，则图片上下移动; X轴上对应图片左右移动。
    mCamera.translate(0.0f, 0.0f, 100.0f);
    // As the angle of the view gets less, zoom in
    if (rotation < mMaxRotationAngle) {
      float zoomAmount = (float) (mMaxZoom + (rotation * 1.5));
      mCamera.translate(0.0f, 0.0f, zoomAmount);
    }
    mCamera.rotateY(rotationAngle); // rotationAngle 为正，沿y轴向内旋转； 为负，沿y轴向外旋转
    mCamera.getMatrix(imageMatrix);
    imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
    imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
    mCamera.restore();
  }
}

3、Activity

Activity中，主要实现自定义Gallery的图片填充ImageAdapter、myGallery选择事件监听、点击事件监听

private void initRes(){
  tvTitle = (TextView) findViewById(R.id.tvTitle);
  gallery = (myGallery) findViewById(R.id.mygallery); // 获取自定义的myGallery控件
  adapter = new ImageAdapter(this);
  adapter.createReflectedImages(); // 创建倒影效果
  gallery.setAdapter(adapter);
  gallery.setOnItemSelectedListener(new OnItemSelectedListener() { // 设置选择事件监听
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
      tvTitle.setText(adapter.titles[position]);
    }
    @Override
    public void onNothingSelected(AdapterView<?> parent) {
    }
  });
  gallery.setOnItemClickListener(new OnItemClickListener() { // 设置点击事件监听
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
      Toast.makeText(Main.this, "img " + (position+1) + " selected", Toast.LENGTH_SHORT).show();
    }
  });
}

main.xml布局文件中，通过实现自定义的myGallery，来显示图片集合

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >
  <TextView
    android:id="@+id/tvTitle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:textSize="16sp" />
  <com.homer.reflect.myGallery
    android:id="@+id/mygallery"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/tvTitle"
    android:layout_marginTop="10dip" />
</RelativeLayout>

完整实例代码点击此处本站下载。

更多关于Android相关内容感兴趣的读者可查看本站专题：《Android开发动画技巧汇总》、《Android开发入门与进阶教程》及《Android控件用法总结》。

希望本文所述对大家Android程序设计有所帮助。