Android Gallery图片显示和文字提示及Menu 菜单
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Gallery组件主要用于横向显示图像列表，不过按常规做法。Gallery组件只能有限地显示指定的图像。也就是说，如果为Gallery组件指定了10张图像，那么当Gallery组件显示到第10张时，就不会再继续显示了。
代码里带注释，欢迎相互讨论
Layout里的main.xml文件：
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?res/menu/menu.xml文件：
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?<item android:id="@+id/menu_about" android:title="关于我们" android:icon="@drawable/icon_about"/>
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id标签，title是当前菜单的描述，icon是当前菜单的图片
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package com.king.showgallery; 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.Color; import android.graphics.LinearGradient; import android.graphics.Matrix; import android.graphics.Paint; import android.graphics.PorterDuff.Mode; import android.graphics.PorterDuffXfermode; import android.graphics.Shader.TileMode; import android.graphics.Typeface; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.Drawable; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.ImageView.ScaleType; public class ImageAdapter extends BaseAdapter{ private Context mContext; private Integer[] mImageIds; private ImageView[] mImages; private String[] strings; private int width,height; //图片上的提示信息 private String[] textList={"功能说明","项目说明","玩法说明","软件说明","退出","程序更新","兑奖","查询"}; public ImageAdapter(Context c, Integer[] ImageIds) { mContext = c; mImageIds = ImageIds; mImages = new ImageView[mImageIds.length]; } public boolean createReflectedImages() { final int reflectionGap = 4; int index = 0; for (int imageId : mImageIds) { Bitmap originalImage = BitmapFactory.decodeResource(mContext .getResources(), imageId); width = originalImage.getWidth(); height = originalImage.getHeight(); Matrix matrix = new Matrix(); // matrix.setRotate(30); matrix.preScale(1, -1); Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height / 2, width, height / 2, matrix, false); Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888); Canvas canvas = new Canvas(bitmapWithReflection); canvas.drawBitmap(originalImage, 0, 0, null); Paint deafaultPaint = new Paint(); deafaultPaint.setAntiAlias(true); canvas.drawRect(0, height, width, height + reflectionGap, deafaultPaint); canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null); Paint paint = new Paint(); paint.setAntiAlias(true); LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP); paint.setShader(shader); paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint); ImageView imageView = new ImageView(mContext); imageView.setImageBitmap(bitmapWithReflection); imageView.setLayoutParams(new GameGallery.LayoutParams(180, 240)); mImages[index++] = imageView; } return true; } 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) { //给图片添加文字提示信息 Bitmap newb = Bitmap.createBitmap( width,height, Config.ARGB_8888 ); Canvas canvasTemp = new Canvas( newb ); canvasTemp.drawColor(Color.alpha(0)); Paint p = new Paint(); String familyName = "宋体"; Typeface font = Typeface.create(familyName, Typeface.BOLD); p.setColor(Color.WHITE); p.setTypeface(font); p.setTextSize(30); canvasTemp.drawText(textList[position], 40,80, p); Drawable drawable = new BitmapDrawable(newb); mImages[position].setBackgroundDrawable(drawable); return mImages[position]; } public float getScale(boolean focused, int offset) { return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset))); } }?在ImageAdapter类中有两个非常重要的方法：getCount和getView。其中getCount方法用于返回图像总数，要注意的是，这个总数不能大于图像的实际数（可以小于图像的实际数），否则会抛出越界异常。当Gallery组件要显示某一个图像时，就会调用getView方法，并将当前的图像索引（position参数）传入该方法。一般getView方法用于返回每一个显示图像的组件（ImageView对象）。从这一点可以看出，Gallery组件是即时显示图像的，而不是一下将所有的图像都显示出来。在getView方法中除了创建了ImageView对象，还用从resIds数组中获得了相应的图像资源ID来设置在ImageView中显示的图像。最后还设置了Gallery组件的背景显示风格。
在ImageAdapter里给图片添加文字信息，注意
1.Bitmap，可以来自资源/文件，也可以在程序中创建，实际上的功能相当于图片的存储空间；?
2.Canvas，紧密与Bitmap联系，把Bitmap比喻内容的话，那么Canvas就是提供了众多方法操作Bitamp的平台；?
3.Paint，与Canvas紧密联系，是"画板"上的笔刷工具，也用于设置View控件上的样式；?
4.Drawable，如果说前三者是看不见地在内存中画图，那么Drawable就是把前三者绘图结果表现出来的接口。Drawable多个子类，例如：位图(BitmapDrawable)、图形(ShapeDrawable)、图层(LayerDrawable)等。??
