关于android gallery 滑动过快的解决办法（菜鸟级别的）

    以前从来没关心过这个问题，自己做过的一个应用上用到类似效果，当时也是因为gallery滑动的过快，就没有研究这东西怎么避免，就用了imageView 单独写了一个效果。

     当然，这个也可以用ImageSwitcher来处理，也能达到相同的效果。。可就是因为自己的一时懒惰，悲剧就那么发生了，在一次面试的时候，有个很强势的面试官，说只能用gallery写这个效果怎么解决，当时没想太明白，回来就研究了一下，结果发现是那么的简单。。。。

     效果图

该demo 自定义了galley 做了滑动处理和3D的显示效果 

下面上代码

布局文件

main.xml

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

    <com.test.galleryUtil.GalleryFlow
        android:id="@+id/Gallery01"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
    </com.test.galleryUtil.GalleryFlow>

</LinearLayout>

Activity类

Gallery3DActivity.class

package com.test.gallerytest;


import com.test.galleryUtil.GalleryFlow;


import android.app.Activity;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader.TileMode;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.Toast;


public class Gallery3DActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Integer[] images = { R.drawable.item1, R.drawable.item10, R.drawable.item2, R.drawable.item3, R.drawable.item4, R.drawable.item5, R.drawable.item6, R.drawable.item7, R.drawable.item8,
R.drawable.item9 };


ImageAdapter adapter = new ImageAdapter(this, images);


adapter.createReflectedImages();// 创建倒影效果


GalleryFlow galleryFlow = (GalleryFlow) this.findViewById(R.id.Gallery01);


galleryFlow.setFadingEdgeLength(0);


galleryFlow.setSpacing(-100); // 图片之间的间距


galleryFlow.setAdapter(adapter);


galleryFlow.setOnItemClickListener(new OnItemClickListener()
{


public void onItemClick(AdapterView<?> parent, View view, int position, long id) {


Toast.makeText(getApplicationContext(), String.valueOf(position), Toast.LENGTH_SHORT).show();


}
});


galleryFlow.setSelection(4);
}


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];


}


/**
* 
* 创建倒影效果
* 
* @return
*/


public boolean createReflectedImages() {


// 倒影图和原图之间的距离


final int reflectionGap = 4;


int index = 0;


for (int imageId : mImageIds)
{


// 返回原图解码之后的bitmap对象


Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), imageId);


int width = originalImage.getWidth();


int height = originalImage.getHeight();


// 创建矩阵对象


Matrix matrix = new Matrix();


// 指定一个角度以0,0为坐标进行旋转


// matrix.setRotate(30);


// 指定矩阵(x轴不变,y轴相反)


matrix.preScale(1, -1);


// 将矩阵应用到该原图之中,返回一个宽度不变,高度为原图1/2的倒影位图


Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,


height / 2, width, height / 2, matrix, false);


// 创建一个宽度不变,高度为原图+倒影图高度的位图


Bitmap bitmapWithReflection = Bitmap.createBitmap(width,


(height + height / 2), Config.ARGB_8888);


// 将上面创建的位图初始化到画布


Canvas canvas = new Canvas(bitmapWithReflection);


canvas.drawBitmap(originalImage, 0, 0, null);


Paint deafaultPaint = new Paint();


deafaultPaint.setAntiAlias(false);


// canvas.drawRect(0, height, width, height +
// reflectionGap,deafaultPaint);


canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);


Paint paint = new Paint();


paint.setAntiAlias(false);


/**
* 
* 参数一：为渐变起初点坐标x位置,
* 
* 参数二：为y轴位置,
* 
* 参数三和四：分辨对应渐变终点,
* 
* 最后参数为平铺方式,
* 
* 这里设置为镜像Gradient是基于Shader类,所以我们通过Paint的setShader方法来设置这个渐变
*/


LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0,


bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.MIRROR);


// 设置阴影


paint.setShader(shader);


paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN));


// 用已经定义好的画笔构建一个矩形阴影渐变效果


canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint);


// 创建一个ImageView用来显示已经画好的bitmapWithReflection


ImageView imageView = new ImageView(mContext);


imageView.setImageBitmap(bitmapWithReflection);


// 设置imageView大小 ,也就是最终显示的图片大小


imageView.setLayoutParams(new GalleryFlow.LayoutParams(300, 400));


// imageView.setScaleType(ScaleType.MATRIX);


mImages[index++] = imageView;


}


return true;


}


@SuppressWarnings("unused")
private Resources getResources() {


return null;


}


public int getCount() {


return mImageIds.length;


}


public Object getItem(int position) {


return position;


}


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)));


}


}

}

自定义gallery类

package com.test.galleryUtil;


import android.content.Context;
import android.graphics.Camera;
import android.graphics.Matrix;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Transformation;
import android.widget.Gallery;
import android.widget.ImageView;


public class GalleryFlow extends Gallery {


private Camera mCamera = new Camera();// 相机类


private int mMaxRotationAngle = 60;// 最大转动角度


private int mMaxZoom = -300;// //最大缩放值


private int mCoveflowCenter;// 半径值


public GalleryFlow(Context context)
{


super(context);


// 支持转换 ,执行getChildStaticTransformation方法


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;


}


private int getCenterOfCoverflow() {


return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2


+ getPaddingLeft();


}


private static int getCenterOfView(View view) {


System.out.println("view left ：" + view.getLeft());


System.out.println("view width ：" + view.getWidth());


return view.getLeft() + view.getWidth() / 2;


}


// 控制gallery中每个图片的旋转(重写的gallery中方法)


protected boolean getChildStaticTransformation(View child, Transformation t) {


// 取得当前子view的半径值


final int childCenter = getCenterOfView(child);


System.out.println("childCenter：" + childCenter);


final int childWidth = child.getWidth();


// 旋转角度


int rotationAngle = 0;


// 重置转换状态


t.clear();


// 设置转换类型


t.setTransformationType(Transformation.TYPE_MATRIX);


// 如果图片位于中心位置不需要进行旋转


if (childCenter == mCoveflowCenter)
{


transformImageBitmap((ImageView) child, t, 0);


} else
{


// 根据图片在gallery中的位置来计算图片的旋转角度


rotationAngle = (int) (((float) (mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);


System.out.println("rotationAngle：" + rotationAngle);


// 如果旋转角度绝对值大于最大旋转角度返回(-mMaxRotationAngle或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) {


// 对效果进行保存


mCamera.save();


final Matrix imageMatrix = t.getMatrix();


// 图片高度


final int imageHeight = child.getLayoutParams().height;


// 图片宽度


final int imageWidth = child.getLayoutParams().width;


// 返回旋转角度的绝对值


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);


}


// 在Y轴上旋转,对应图片竖向向里翻转.


// 如果在X轴上旋转,则对应图片横向向里翻转.


mCamera.rotateY(rotationAngle);


mCamera.getMatrix(imageMatrix);


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


imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));


mCamera.restore();


}


@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
// TODO Auto-generated method stub
return super.onScroll(e1, e2, distanceX * 1, distanceY);
}


// 实现短距离滑动
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
// int kEvent;
// if (isScrollingLeft(e1, e2)) {
// // Check if scrolling left
// kEvent = KeyEvent.KEYCODE_DPAD_LEFT;
// } else {
// // Otherwise scrolling right
// kEvent = KeyEvent.KEYCODE_DPAD_RIGHT;
// }
// onKeyDown(kEvent, null);
// return true;
return false;
}


private boolean isScrollingLeft(MotionEvent e1, MotionEvent e2) {
return e2.getX() > e1.getX();
}


}

demo下载地址 ： http://download.csdn.net/download/eye_hello/4547509