Android 滑動效果進階篇（六）—— 倒影效果

上篇介紹了使用Animation實現3D動畫旋轉翻頁效果，現在介紹圖片倒影實現，先看效果圖

本示例主要通過自定義Gallery和ImageAdapter（繼承自BaseAdapter）實現

1、倒影繪製

ImageAdapter繼承自BaseAdapter，詳細實現可見 Android 滑動效果入門篇（二）—— Gallery 這裏重點介紹倒影原理及實現

倒影原理：

倒影效果是主要由原圖+間距+倒影三部分組成，高度大約爲原圖的3/2（原圖爲1、倒影爲1/2）

原圖，就是我們看到了最開始的圖片

間距，是原圖與倒影之間的間隙，如：reflectionGap = 4;

倒影，是原圖下半部分1/2高度，通過矩陣變換matrix.preScale(1, -1); 獲取倒立圖片，然後再加上線性遮罩和陰影實現

倒影實現：

/** 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);   // 獲取原始圖片
        int width = originalImage.getWidth();
        int height = originalImage.getHeight();

        Matrix matrix = new Matrix();
        matrix.preScale(1, -1);         // 圖片矩陣變換（從低部向頂部的倒影）
        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);   // 截取原圖下半部分
        Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888);          // 創建倒影圖片（高度爲原圖3/2）

        Canvas canvas = new Canvas(bitmapWithReflection);   // 繪製倒影圖（原圖 + 間距 + 倒影）
        canvas.drawBitmap(originalImage, 0, 0, null);       // 繪製原圖
        Paint paint = new Paint();
        canvas.drawRect(0, height, width, height + reflectionGap, paint);       // 繪製原圖與倒影的間距
        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);    // 繪製倒影圖

        paint = new Paint();
        LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
        paint.setShader(shader);    // 線性漸變效果
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));     // 倒影遮罩效果
        canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint);     // 繪製倒影的陰影效果

        ImageView imageView = new ImageView(mContext);
        imageView.setImageBitmap(bitmapWithReflection);     // 設置倒影圖片
        imageView.setLayoutParams(new myGallery.LayoutParams(180, 240));
        imageView.setScaleType(ScaleType.MATRIX);
        mImages[index++] = imageView;
    }
    return true;
}

	/** 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);	// 獲取原始圖片
			int width = originalImage.getWidth();
			int height = originalImage.getHeight();

			Matrix matrix = new Matrix();
			matrix.preScale(1, -1);			// 圖片矩陣變換（從低部向頂部的倒影）
			Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);	// 截取原圖下半部分
			Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888);			// 創建倒影圖片（高度爲原圖3/2）

			Canvas canvas = new Canvas(bitmapWithReflection);	// 繪製倒影圖（原圖 + 間距 + 倒影）
			canvas.drawBitmap(originalImage, 0, 0, null);		// 繪製原圖
			Paint paint = new Paint();
			canvas.drawRect(0, height, width, height + reflectionGap, paint);		// 繪製原圖與倒影的間距
			canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);	// 繪製倒影圖

			paint = new Paint();
			LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
			paint.setShader(shader);	// 線性漸變效果
			paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));		// 倒影遮罩效果
			canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint);		// 繪製倒影的陰影效果

			ImageView imageView = new ImageView(mContext);
			imageView.setImageBitmap(bitmapWithReflection);		// 設置倒影圖片
			imageView.setLayoutParams(new myGallery.LayoutParams(180, 240));
			imageView.setScaleType(ScaleType.MATRIX);
			mImages[index++] = imageView;
		}
		return true;
	}

2、myGallery

自定義Gallery來實現倒影圖片的瀏覽與選擇

public class myGallery extends Gallery {

    private Camera mCamera = new Camera();
    private int mMaxRotationAngle = 60;     // 最大旋轉角度 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;
    }

    /** 獲取Gallery的中心x */
    private int getCenterOfCoverflow() {
        return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
    }

    /** 獲取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 都變換

        if (childCenter == mCoveflowCenter) {   // 正中間的childView
            transformImageBitmap((ImageView) child, trans, 0);
        } else {        // 兩側的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軸上正向移動camera的視角，實際效果爲放大圖片; 如果在Y軸上移動，則圖片上下移動; X軸上對應圖片左右移動。
        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 爲正，沿y軸向內旋轉； 爲負，沿y軸向外旋轉

        mCamera.getMatrix(imageMatrix);
        imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
        imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));

        mCamera.restore();
    }
}

public class myGallery extends Gallery {

	private Camera mCamera = new Camera();
	private int mMaxRotationAngle = 60;		// 最大旋轉角度 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;
	}

	/** 獲取Gallery的中心x */
	private int getCenterOfCoverflow() {
		return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
	}

	/** 獲取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 都變換

		if (childCenter == mCoveflowCenter) {	// 正中間的childView
			transformImageBitmap((ImageView) child, trans, 0);	
		} else {		// 兩側的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軸上正向移動camera的視角，實際效果爲放大圖片; 如果在Y軸上移動，則圖片上下移動; X軸上對應圖片左右移動。
		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 爲正，沿y軸向內旋轉； 爲負，沿y軸向外旋轉
		
		mCamera.getMatrix(imageMatrix);
		imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
		imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
		
		mCamera.restore();
	}
}

3、Activity

Activity中，主要實現自定義Gallery的圖片填充ImageAdapter、myGallery選擇事件監聽、點擊事件監聽

private void initRes(){
    tvTitle = (TextView) findViewById(R.id.tvTitle);
    gallery = (myGallery) findViewById(R.id.mygallery);     // 獲取自定義的myGallery控件

    adapter = new ImageAdapter(this);
    adapter.createReflectedImages();    // 創建倒影效果
    gallery.setAdapter(adapter);

    gallery.setOnItemSelectedListener(new OnItemSelectedListener() {    // 設置選擇事件監聽
        @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() {          // 設置點擊事件監聽
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Toast.makeText(Main.this, "img " + (position+1) + " selected", Toast.LENGTH_SHORT).show();
        }
    });
}

	private void initRes(){
		tvTitle = (TextView) findViewById(R.id.tvTitle);
		gallery = (myGallery) findViewById(R.id.mygallery);		// 獲取自定義的myGallery控件

		adapter = new ImageAdapter(this); 	
		adapter.createReflectedImages();	// 創建倒影效果
		gallery.setAdapter(adapter);
		
		gallery.setOnItemSelectedListener(new OnItemSelectedListener() {	// 設置選擇事件監聽
			@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() {			// 設置點擊事件監聽
			@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佈局文件中，通過實現自定義的myGallery，來顯示圖片集合

<?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>

<?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>

源碼下載

參考推薦：

Android實現圖片的倒影效果

Android中圖片倒影、圓角效果重繪