Android之gallery 常见2种使用方法和3D效果总结

我们有时候在iPhone手机上或者Windows上面看到动态的图片，可以通过鼠标或者手指触摸来移动它，产生动态的图片滚动效果，还可以根据你的点击或者触摸触发其他事件响应。同样的，在Android中也提供这这种实现，这就是通过Gallery在UI上实现缩略图浏览器。

一般情况下，我们在Android中要用到类似这种图片容器的控件，都需要为它指定一个适配器，让它可以把内容按照我们定义的方式来显示，因此我们来给它加一个适配器，至于这个适配器如何实现，后面接着来操作，这里只需知道这个适配器的类叫ImageGalleryAdapter 。 gallery.setAdapter(new ImageGalleryAdapter (this));

下面介绍常用2种用法：

第一种方法：

第一步：设计xml布局文件

代码如下：main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Gallery
android:id="@+id/myGallery"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:spacing="3px"
android:text="@string/hello" />
</LinearLayout>

第二步：自定义一个适配器，这个适配器继承BaseAdapter这个类
代码如下：

package net.loonggg.gallery;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class ImageGalleryAdapter extends BaseAdapter {
private Context context;
// 里面所有的方法表示的是可以根据指定的显示图片的数量,进行每个图片的处理
private int[] image = new int[] { R.drawable.ispic_a, R.drawable.ispic_b,
R.drawable.ispic_c, R.drawable.ispic_d, R.drawable.ispic_e };

public ImageGalleryAdapter(Context context) {
this.context = context;
}

public int getCount() { // 取得要显示内容的数量
return image.length;
}

public Object getItem(int position) { // 每个资源的位置
return image[position];
}

public long getItemId(int position) { // 取得每个项的ID
return image[position];
}

// 将资源设置到一个组件之中，很明显这个组件是ImageView
public View getView(int position, View convertView, ViewGroup parent) {
ImageView iv = new ImageView(context);
iv.setBackgroundColor(0xFFFFFFFF);
iv.setImageResource(image[position]);// 给ImageView设置资源
iv.setScaleType(ImageView.ScaleType.CENTER);// 设置对齐方式
iv.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT));
return iv;
}
}

第三步：主方法：

package net.loonggg.gallery;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Gallery;
import android.widget.Toast;

public class GalleryActivity extends Activity {
private Gallery myGallery;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myGallery = (Gallery) findViewById(R.id.myGallery);
myGallery.setAdapter(new ImageGalleryAdapter(this));
myGallery.setOnItemClickListener(new OnItemClickListenerImpl());
}

private class OnItemClickListenerImpl implements OnItemClickListener {

public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
Toast.makeText(GalleryActivity.this, String.valueOf(position),
Toast.LENGTH_SHORT).show();
}

}
}

第二种方法

第一步：设计xml布局文件 
代码如下：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:gravity="bottom"
android:orientation="vertical" >

<ImageSwitcher
android:id="@+id/is"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ImageSwitcher>

<Gallery
android:id="@+id/myGallery"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:spacing="3px" />

</LinearLayout>

gallery_item.xml文件：

代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#FFFFFF"
android:orientation="horizontal" >

<ImageView
android:id="@+id/iv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="center" />

</LinearLayout>

第二步：MainActivity

代码如下：

package net.loonggg.gallery2;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.SimpleAdapter;
import android.widget.ViewSwitcher.ViewFactory;

public class MainActivity extends Activity {
private ImageSwitcher is;
private Gallery gallery;
private SimpleAdapter adapter;
private List<Map<String, Integer>> list = new ArrayList<Map<String, Integer>>();

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
is = (ImageSwitcher) findViewById(R.id.is);
is.setFactory(new ViewFactoryImpl());
initAdapter();
gallery = (Gallery) findViewById(R.id.myGallery);
gallery.setAdapter(adapter); // 为gallery设置合适的适配器
gallery.setOnItemClickListener(new OnItemClickListenerImpl());

}

public class OnItemClickListenerImpl implements OnItemClickListener { // gallery的点击事件

@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
Map<String, Integer> map = (Map<String, Integer>) parent
.getAdapter().getItem(position);
is.setImageResource(map.get("image"));
}

}

public void initAdapter() { // 这个方法的功能是：从R.java文件中获取图片资源的id,如果资源图片数量比较多，用数组的方法一一定义，就不太合适，这种方法最好了。
Field[] fields = R.drawable.class.getDeclaredFields();
for (int x = 0; x < fields.length; x++) {
if (fields[x].getName().startsWith("ispic_")) { // 根据图片的名称取出想要的图片
Map<String, Integer> map = new HashMap<String, Integer>();
try {
map.put("image", fields[x].getInt(R.drawable.class));
} catch (Exception e) {
e.printStackTrace();
}
list.add(map);
}
}
adapter = new SimpleAdapter(MainActivity.this, list,
R.layout.grid_item, new String[] { "image" },
new int[] { R.id.iv });
}

public class ViewFactoryImpl implements ViewFactory {

@Override
public View makeView() {
ImageView iv = new ImageView(MainActivity.this);
iv.setBackgroundColor(0xFFFFFFFF);
iv.setScaleType(ImageView.ScaleType.CENTER);
iv.setLayoutParams(new ImageSwitcher.LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
return iv;
}

}
}

Android gallery 3D效果
一  创建倒影效果
二 扩装gallery 
三 完整代码
先看效果，不然就是无图无真相了。

一，创建倒影效果

这个基本思路是：

1，创建一个源图一样的图，利用martrix将图片旋转180度。这个倒影图的高是源图的一半。

Matrix matrix = new Matrix();

// 1表示放大比例，不放大也不缩小。
// -1表示在y轴上相反，即旋转180度。
matrix.preScale(1, -1);

Bitmap reflectionBitmap = Bitmap.createBitmap(
srcBitmap,
0,
srcBitmap.getHeight() / 2,  // top为源图的一半
srcBitmap.getWidth(),       // 宽度与源图一样
srcBitmap.getHeight() / 2,  // 高度与源图的一半
matrix,
false);

2，创建一个最终效果的图，即源图 + 间隙 + 倒影。

final int REFLECTION_GAP = 5;

Bitmap bitmapWithReflection = Bitmap.createBitmap(
reflectionWidth,
srcHeight + reflectionHeight + REFLECTION_GAP,
Config.ARGB_8888);

3，依次将源图、倒影图绘制在最终的bitmap上面。

Canvas canvas = new Canvas(bitmapWithReflection);

// Draw the original bitmap.
canvas.drawBitmap(srcBitmap, 0, 0, null);

// Draw the reflection bitmap.
canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null);

4，创建LinearGradient，从而给定一个由上到下的渐变色。

Paint paint = new Paint();
paint.setAntiAlias(true);
LinearGradient shader = new LinearGradient(
0,
srcHeight,
0,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
0x70FFFFFF,
0x00FFFFFF,
TileMode.MIRROR);
paint.setShader(shader);
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN));

// Draw the linear shader.
canvas.drawRect(
0,
srcHeight,
srcWidth,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
paint);

二，扩展Gallery

扩展系统的gallery，我们需要重写两个方法，getChildStaticTransformation()和getChildDrawingOrder()，同时，要使这两个方法能被调用，必须执行如下两行代码，文档上面是有说明的。

// Enable set transformation.
this.setStaticTransformationsEnabled(true);
// Enable set the children drawing order.
this.setChildrenDrawingOrderEnabled(true);

getChildDrawingOrder的实现

@Override
protected int getChildDrawingOrder(int childCount, int i)
{
// Current selected index.
int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition();
if (selectedIndex < 0)
{
return i;
}

if (i < selectedIndex)
{
return i;
}
else if (i >= selectedIndex)
{
return childCount - 1 - i + selectedIndex;
}
else
{
return i;
}
}

这里为什么要计算drawing order，因为从上图中看到，我们的效果是：中间左边的顺序是 0， 1， 2，右边的child覆盖左边的child，而在中间右边的顺序正好相反，左边的覆盖右边的，所以我们要重写这个方法，而gallery自身的实现，不是这种效果。
getChildStaticTransformation的实现

?

@Override
protected boolean getChildStaticTransformation(View child, Transformation t)
{
super.getChildStaticTransformation(child, t);

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

int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);

// If the child is in the center, we do not rotate it.
if (childCenter == mCoveflowCenter)
{
transformImageBitmap(child, t, 0);
}
else
{
// Calculate the rotation angle.
rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);

// Make the angle is not bigger than maximum.
if (Math.abs(rotationAngle) > mMaxRotationAngle)
{
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
}

transformImageBitmap(child, t, rotationAngle);
}

return true;
}

这个方法就是根据child来计算它的transformation（变换），我们需要去修改它里面的matrix，从而达到旋转的效果。根据位置和角度来计算的matrix的方法写在另外一个方法transformImageBitmap中实现。
transformImageBitmap()的实现

private void transformImageBitmap(View child, Transformation t, int rotationAngle)
{
mCamera.save();

final Matrix imageMatrix = t.getMatrix();
final int imageHeight = child.getHeight();
final int imageWidth  = child.getWidth();
final int rotation    = Math.abs(rotationAngle);

// Zoom on Z axis.
mCamera.translate(0, 0, mMaxZoom);

if (rotation < mMaxRotationAngle)
{
float zoomAmount = (float)(mMaxZoom + rotation * 1.5f);
mCamera.translate(0, 0, zoomAmount);
}

// Rotate the camera on Y axis.
mCamera.rotateY(rotationAngle);
// Get the matrix from the camera, in fact, the matrix is S (scale) transformation.
mCamera.getMatrix(imageMatrix);

// The matrix final is T2 * S * T1, first translate the center point to (0, 0),
// then scale, and then translate the center point to its original point.
// T * S * T

// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));

mCamera.restore();
}

这里，简单说明一个，

        第一，先在Z轴上平称，其实就是得到一个缩放矩阵变换，我这里简写为 S。

        第二，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，记为 R 。经过这两步，此时调用mCamera.getMatrix(imageMatrix); 从Camera中得到matrix，此时这个矩阵中包含了S * R。

        第三，最关键是下面两句       

// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));

  由于这里涉及到旋转与缩放，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，所以，我们最终的矩阵变换应该是这样的：

        M = T * （S * R） * T1   （这里在T1表示与T相反）。

三，完整代码

GalleryFlow.java

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

public class GalleryFlow extends Gallery
{
/**
* The camera class is used to 3D transformation matrix.
*/
private Camera mCamera = new Camera();

/**
* The max rotation angle.
*/
private int mMaxRotationAngle = 60;

/**
* The max zoom value (Z axis).
*/
private int mMaxZoom = -120;

/**
* The center of the gallery.
*/
private int mCoveflowCenter = 0;

public GalleryFlow(Context context)
{
this(context, null);
}

public GalleryFlow(Context context, AttributeSet attrs)
{
this(context, attrs, 0);
}

public GalleryFlow(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);

// Enable set transformation.
this.setStaticTransformationsEnabled(true);
// Enable set the children drawing order.
this.setChildrenDrawingOrderEnabled(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;
}

@Override
protected int getChildDrawingOrder(int childCount, int i)
{
// Current selected index.
int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition();
if (selectedIndex < 0)
{
return i;
}

if (i < selectedIndex)
{
return i;
}
else if (i >= selectedIndex)
{
return childCount - 1 - i + selectedIndex;
}
else
{
return i;
}
}

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

private int getCenterOfView(View view)
{
return view.getLeft() + view.getWidth() / 2;
}

@Override
protected boolean getChildStaticTransformation(View child, Transformation t)
{
super.getChildStaticTransformation(child, t);

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

int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);

// If the child is in the center, we do not rotate it.
if (childCenter == mCoveflowCenter)
{
transformImageBitmap(child, t, 0);
}
else
{
// Calculate the rotation angle.
rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);

// Make the angle is not bigger than maximum.
if (Math.abs(rotationAngle) > mMaxRotationAngle)
{
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
}

transformImageBitmap(child, t, rotationAngle);
}

return true;
}

private int getCenterOfCoverflow()
{
return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
}

private void transformImageBitmap(View child, Transformation t, int rotationAngle)
{
mCamera.save();

final Matrix imageMatrix = t.getMatrix();
final int imageHeight = child.getHeight();
final int imageWidth  = child.getWidth();
final int rotation    = Math.abs(rotationAngle);

// Zoom on Z axis.
mCamera.translate(0, 0, mMaxZoom);

if (rotation < mMaxRotationAngle)
{
float zoomAmount = (float)(mMaxZoom + rotation * 1.5f);
mCamera.translate(0, 0, zoomAmount);
}

// Rotate the camera on Y axis.
mCamera.rotateY(rotationAngle);
// Get the matrix from the camera, in fact, the matrix is S (scale) transformation.
mCamera.getMatrix(imageMatrix);

// The matrix final is T2 * S * T1, first translate the center point to (0, 0),
// then scale, and then translate the center point to its original point.
// T * S * T

// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));

mCamera.restore();
}
}

BitmapUtil.java

package com.lee.gallery3d.utils;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.Drawable;

public class BitmapUtil
{
public static Bitmap createReflectedBitmap(Bitmap srcBitmap)
{
if (null == srcBitmap)
{
return null;
}

// The gap between the reflection bitmap and original bitmap.
final int REFLECTION_GAP = 4;

int srcWidth  = srcBitmap.getWidth();
int srcHeight = srcBitmap.getHeight();
int reflectionWidth  = srcBitmap.getWidth();
int reflectionHeight = srcBitmap.getHeight() / 2;

if (0 == srcWidth || srcHeight == 0)
{
return null;
}

// The matrix
Matrix matrix = new Matrix();
matrix.preScale(1, -1);

try
{
// The reflection bitmap, width is same with original's, height is half of original's.
Bitmap reflectionBitmap = Bitmap.createBitmap(
srcBitmap,
0,
srcHeight / 2,
srcWidth,
srcHeight / 2,
matrix,
false);

if (null == reflectionBitmap)
{
return null;
}

// Create the bitmap which contains original and reflection bitmap.
Bitmap bitmapWithReflection = Bitmap.createBitmap(
reflectionWidth,
srcHeight + reflectionHeight + REFLECTION_GAP,
Config.ARGB_8888);

if (null == bitmapWithReflection)
{
return null;
}

// Prepare the canvas to draw stuff.
Canvas canvas = new Canvas(bitmapWithReflection);

// Draw the original bitmap.
canvas.drawBitmap(srcBitmap, 0, 0, null);

// Draw the reflection bitmap.
canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null);

Paint paint = new Paint();
paint.setAntiAlias(true);
LinearGradient shader = new LinearGradient(
0,
srcHeight,
0,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
0x70FFFFFF,
0x00FFFFFF,
TileMode.MIRROR);
paint.setShader(shader);
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN));

// Draw the linear shader.
canvas.drawRect(
0,
srcHeight,
srcWidth,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
paint);

return bitmapWithReflection;
}
catch (Exception e)
{
e.printStackTrace();
}

return null;
}
}