Gallery

       刚开始做这个的时候，对于gallery了解的并不多，看起来一头雾脑 ，不知如何下手，下面我将结合我做的项目浅谈一下我对Gallery的理解

效果图是这样的



1、首先先创建activity_stinkpot.xml文件进行布局，使页面出现大体框架

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/layout_bg"
android:orientation="vertical" >

<RelativeLayout
android:layout_width="match_parent"
android:layout_height="60dp"
android:padding="5dp" >

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:layout_weight="1"
android:text="奇奇怪怪的馬桶"
android:textColor="#FFFFFF"
android:textSize="20sp"
android:textStyle="bold" />
</RelativeLayout>

<ImageView
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@color/black" />

<ImageView
android:id="@+id/stinkpot_img"
android:layout_marginTop="20dip"
android:layout_width="250dip"
android:layout_height="250dip"
android:layout_gravity="center_horizontal"
/>

<com.example.gallery.GalleryFlow
android:id="@+id/mgallery"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_gravity="center_horizontal"
/>

</LinearLayout>
并对一些空件子项自定义

2、自定义Gallery来实现图片的浏览与选择

 public class GalleryFlow 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 GalleryFlow(Context context) {
super(context);
this.setStaticTransformationsEnabled(true);
}

public GalleryFlow(Context context, AttributeSet attrs) {
super(context, attrs);
this.setStaticTransformationsEnabled(true);
}

public GalleryFlow(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
private int getCenterOfCoverflow() {
return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2
+ getPaddingLeft();
}
//获取view中心
private static int getCenterOfView(View view) {
return view.getLeft() + view.getWidth() / 2;
}

protected boolean getChildStaticTransformation(View child, Transformation t) {

final int childCenter = getCenterOfView(child);
final int childWidth = child.getWidth();
int rotationAngle = 0;

t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);//alpha和matrix都变换

if (childCenter == mCoveflowCenter) {//正中间的childView
transformImageBitmap((ImageView) child, t, 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, t, rotationAngle);
}

return true;
}

protected void onSizeChanged(int w, int h, int oldw, int oldh) {
mCoveflowCenter = getCenterOfCoverflow();
super.onSizeChanged(w, h, oldw, oldh);
}

private void transformImageBitmap(ImageView child, Transformation t,
int rotationAngle) {
mCamera.save();
final Matrix imageMatrix = t.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();
}
}
1）先在Z轴上平称，其实就是得到一个缩放矩阵变换
2）是利用camera这个类来生成matrix，其实mCamera.rotateY就是围绕Y轴旋转。这里生成了一个旋转矩阵，此时调用mCamera.getMatrix(imageMatrix); 从Camera中得到matrix，

3）最后几句涉及到旋转与缩放，缩放操作其实应该是针对Child中点进行了，这里就是作一个平衡操作，我们必须是先平移，再缩放，再平移回原来位置

3、倒影的绘制

创建ImageAdapter继承自BaseAdapter，倒影效果是主要由原图+间距+倒影三部分组成，

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，我们这将此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

public class ImageAdapter extends BaseAdapter {

int mGalleryItemBackground;
private Context mContext;
private Integer[] mImageIds;
private ImageView[] mImages;

public ImageAdapter(Context c, Integer[] ImageIds) {
mContext = c;
mImageIds = ImageIds;
mImages = new ImageView[mImageIds.length];
}
//反射倒影
public boolean createReflectedImages() {
final int reflectionGap = 4;
int index = 0;

for (int imageId : mImageIds) {
Bitmap originalImage = BitmapFactory.decodeResource(
mContext.getResources(), imageId);//获取原图片
int width = originalImage.getWidth();
int height = originalImage.getHeight();

Matrix matrix = new Matrix();
matrix.preScale(1, -1);//图片矩阵变换，从底部到顶部倒影

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); // 绘制倒影图即原图 + 间距 + 倒影

canvas.drawBitmap(originalImage, 0, 0, null);//绘制原图

Paint deafaultPaint = new Paint();
canvas.drawRect(0, height, width, height + reflectionGap,
deafaultPaint); //绘制原图与倒影的间距

canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null); // 绘制倒影图

Paint 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 GalleryFlow.LayoutParams(180, 240));
// imageView.setScaleType(ScaleType.MATRIX);
mImages[index++] = imageView;
}
return true;
}

private Resources getResources() {
// TODO Auto-generated method stub
return null;
}
//获取图片位置
public int getCount() {
return mImageIds.length;
}

public Object getItem(int position) {
return position;
}
//获取图片Id
public long getItemId(int position) {
return position;
}

public View getView(int position, View convertView, ViewGroup parent) {
return mImages[position];
}

public float getScale(boolean focused, int offset) {
return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));
}

}

4、Activity的主要图片点击事件
<
4000
/p>

public class StinkPot_Activity extends Activity{

private ImageView showImage;
GalleryFlow galleryFlow;
ImageAdapter adapter;
//图片组
Integer[] images = { R.drawable.stinkpot001, R.drawable.stinkpot002,
R.drawable.stinkpot003, R.drawable.stinkpot004, R.drawable.stinkpot005,
R.drawable.stinkpot006, R.drawable.stinkpot007, R.drawable.stinkpot008,
R.drawable.stinkpot009, R.drawable.stinkpot010, R.drawable.stinkpot011 };

@Override
protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_stinkpot);

showImage=(ImageView)findViewById(R.id.stinkpot_img);
showImage.setImageResource(images[0]);
adapter = new ImageAdapter(this, images);
adapter.createReflectedImages();
// 图片单击事件
AdapterView.OnItemClickListener listener = new AdapterView.OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO 自动生成的方法存根

showImage.setImageResource(images[position]);
// Toast.makeText(GalleryActivity.this, "图片 " + (position + 1),
// Toast.LENGTH_SHORT).show();
}

};

galleryFlow = (GalleryFlow) findViewById(R.id.mgallery);
galleryFlow.setAdapter(adapter);
galleryFlow.setOnItemClickListener(listener);// 注册图片单击

}
}