Android Gallery图片显示和文字提示及Menu 菜单

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：

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:background="@drawable/background_port" 
    > 
     
    <ImageButton android:src="@drawable/login" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:id="@+id/login" 
        android:background="#0000"/> 
         
    <com.king.showgallery.GameGallery android:id="@+id/imgGallery" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_centerHorizontal="true" 
        android:layout_alignParentBottom="true"/> 
         
</RelativeLayout>

 res/menu/menu.xml文件：

<?xml version="1.0" encoding="UTF-8"?> 
<menu xmlns:android="http://schemas.android.com/apk/res/android"> 
    <item android:id="@+id/menu_update" android:title="程序升级" android:icon="@drawable/icon_appupdate"/> 
    <item android:id="@+id/menu_download" android:title="下载中心" android:icon="@drawable/icon_download_center"/> 
    <item android:id="@+id/menu_feedback" android:title="用户反馈" android:icon="@drawable/icon_feedback"/> 
    <item android:id="@+id/menu_recommend" android:title="好友推荐" android:icon="@drawable/icon_recommend"/> 
    <item android:id="@+id/menu_about" android:title="关于我们" android:icon="@drawable/icon_about"/> 
</menu>

id标签，title是当前菜单的描述，icon是当前菜单的图片

package com.king.showgallery; 
import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.View; 
import android.view.Window; 
import android.view.WindowManager; 
import android.widget.AdapterView; 
import android.widget.TextView; 
import android.widget.Toast; 
import android.widget.AdapterView.OnItemClickListener; 
public class GalleryActivity extends MenuActivity { 
    //imgList里装载需要显示的图片 
    private Integer[] imgList={R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1,R.drawable.tab_selected_1}; 
    private Toast toast; 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
         
        //设置全屏 
        requestWindowFeature(Window.FEATURE_NO_TITLE); 
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); 
        setContentView(R.layout.main); 
         
        ImageAdapter adapter = new ImageAdapter(this, imgList); 
        adapter.createReflectedImages(); 
        GameGallery gameGallery = (GameGallery) findViewById(R.id.imgGallery); 
        gameGallery.setAdapter(adapter); 
         
         
        gameGallery.setOnItemClickListener(new OnItemClickListener() { 
            //AdapterView<?> arg0代表向spinner中加载的一系列字符串或其它事物，是一个适配器，是字符串和Spinner之间的桥梁！而View代表Spinner，int arg2代表ItemId, long arg3代表Item的position！ 
            public void onItemClick(AdapterView<?> arg0, View view, int position, 
                    long arg3) { 
                switch (position) { 
                case 0: 
                    //点击每个图片，根据图片的position，显示不同的内容 
                    toast.makeText(GalleryActivity.this, "this is zero", Toast.LENGTH_SHORT).show(); 
                    break; 
                case 1: 
                    toast.makeText(GalleryActivity.this, "this is one", Toast.LENGTH_SHORT).show();break; 
                case 2: 
                    toast.makeText(GalleryActivity.this, "this is two", Toast.LENGTH_SHORT).show();break; 
                case 3: 
                    toast.makeText(GalleryActivity.this, "this is three", Toast.LENGTH_SHORT).show();break; 
                case 4: 
                    //程序退出事件 
                    Intent startMain = new Intent(Intent.ACTION_MAIN); 
                    startMain.addCategory(Intent.CATEGORY_HOME); 
                    startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
                    startActivity(startMain); 
                    System.exit(0); 
                    break; 
                case 5: 
                    toast.makeText(GalleryActivity.this, "this is five", Toast.LENGTH_SHORT).show();break; 
                case 6: 
                    toast.makeText(GalleryActivity.this, "this is six", Toast.LENGTH_SHORT).show();break; 
                case 7: 
                    toast.makeText(GalleryActivity.this, "this is seven", Toast.LENGTH_SHORT).show();break; 
                default: 
                    break; 
                } 
            } 
        }); 
    } 
}

 对于Android开发我们可以做的尽量MVC化，UI界面和Code逻辑代码分离方式，除了常规的Activity布局可以用xml实现外，菜单Menu也可以通过MenuInflater来映射一个布局文件，相关的创建菜单方法有些不同。

package com.king.showgallery; 
import android.app.Activity; 
import android.content.Context; 
import android.os.Handler; 
import android.util.AttributeSet; 
import android.view.InflateException; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuInflater; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.Toast; 
public class MenuActivity extends Activity{ 
    public boolean onCreateOptionsMenu(Menu menu){ 
        super.onCreateOptionsMenu(menu); 
        //MenuInflater 是用来解析定义在menu 目录下的菜单布局文件 
        MenuInflater inflater=new MenuInflater(getApplicationContext()); 
        inflater.inflate(R.menu.menu, menu); 
        return true; 
    } 
     
    public boolean onOptionsItemSelected(MenuItem item){ 
        String info=""; 
        switch (item.getItemId()) { 
        case R.id.menu_about: 
            //点击当前菜单后显示效果 
            info="isabout"; 
            break; 
             
        case R.id.menu_download: 
            info="isdownload"; 
            break; 
         
        case R.id.menu_feedback: 
            info="isfeedback"; 
            break; 
         
        case R.id.menu_recommend: 
            info="isrecommend"; 
            break; 
             
        case R.id.menu_update: 
            info="isupdate"; 
            break; 
        default: 
            info="null"; 
            break; 
        } 
         
        Toast toast=Toast.makeText(this, info, Toast.LENGTH_SHORT); 
        toast.show(); 
        return super.onOptionsItemSelected(item); 
    } 
     
    protected void setMenuBackground(){ 
        MenuActivity.this.getLayoutInflater().setFactory(new android.view.LayoutInflater.Factory() { 
             
            @Override 
            public View onCreateView(String name, Context context, AttributeSet attrs) { 
                if(name.equalsIgnoreCase("com.android.internal.view.menu.IconMenuItemView")){ 
                    try{ 
                        LayoutInflater f=getLayoutInflater(); 
                        final View view=f.createView(name, null, attrs); 
                        new Handler().post(new Runnable(){ 
                            public void run(){ 
                                view.setBackgroundResource(R.drawable.menu_background); 
                            } 
                        }); 
                        return view; 
                    }catch(InflateException e){ 
                        e.printStackTrace(); 
                    }catch(ClassNotFoundException e){ 
                        e.printStackTrace(); 
                    } 
                } 
                return null; 
            } 
        }); 
    } 
}

package com.king.showgallery; 
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; 
import android.widget.ImageView; 
public class GameGallery extends Gallery{ 
     
    public GameGallery(Context context){ 
        super(context); 
        this.setStaticTransformationsEnabled(true); 
    } 
     
    public GameGallery(Context context,AttributeSet attrs){ 
        super(context,attrs); 
        this.setStaticTransformationsEnabled(true); 
    } 
    public GameGallery(Context context, AttributeSet attrs, int defStyle) { 
        super(context, attrs, defStyle); 
        this.setStaticTransformationsEnabled(true); 
    } 
     
    //mCamera是用来做类3D效果处理,比如z轴方向上的平移,绕y轴的旋转等 
    private Camera mCamera = new Camera(); 
     
    //mMaxRotationAngle是图片绕y轴最大旋转角度,也就是屏幕最边上那两张图片的旋转角度 
    private int mMaxRotationAngle = 60; 
     
    //mMaxZoom是图片在z轴平移的距离,视觉上看起来就是放大缩小的效果. 
    private int mMaxZoom = -120; 
     
    private int mCoveflowCenter; 
    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) { 
            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); 
            if (childCenter == mCoveflowCenter) { 
                    transformImageBitmap((ImageView) child, t, 0); 
            } else { 
                    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); 
            } 
            // 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(); 
    } 
}

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);      during-pregnancy
        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。