android 遮罩层效果

看到一本电子杂志上有遮罩层的效果，感觉很漂亮，以为很麻烦，搜索了很多关于android遮罩层的，也没有得出一点思路，原来就是一个透明的效果，然后上面弹出的控件是透明或者半透明之类的，可以选择颜色，还是#ARBG，其中A就是传说中的透明色的值（可以根据需要设置透明的效果），废话不多说了，发一个简单的Demo吧，是我山寨的那本杂志的效果：（由于杂志内容主要是图片，弹出层才是给出的文字信息，所以我猜测是用Gallery显示的杂志内容）

xml布局文件：

<?xml version="1.0" encoding="utf-8"?>  
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:id="@+id/layout"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent"  
    >  
    <Gallery  
        android:id="@+id/showGallery"  
        android:layout_width="fill_parent"  
        android:layout_height="fill_parent"  
        android:spacing="0dip"  
        />  
    <RelativeLayout  
            android:orientation="horizontal"  
            android:layout_width="fill_parent"  
            android:layout_height="wrap_content"  
            android:layout_gravity="bottom"  
            android:background="#86222222"  
            >  
            <TextView  
                android:id="@+id/titleTextView"  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:layout_toRightOf="@id/secondKillButton" 
                android:text="00000000"
                android:textColor="#ff0000"  
                />  
            <Button  
                android:id="@+id/unfoldButton"  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:layout_alignParentRight="true"  
                android:text="展开"  
                />  
    </RelativeLayout>  
</FrameLayout>   

主要的代码也很简单，还有一个简单的Adapter，有不理解的朋友可以看我之前的blog

package oneRain.UpMagazine;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.TextView;
public class ShowActivity extends Activity
{
    private int i = 1;
    private int pos = 0;
    private List<String> contents = null;
    private static final String DIR = "/mnt/sdcard/UpMagazine/2010/content/";

    //设置是否展开
    private boolean isFolded = true;

    //设置控件
    private FrameLayout layout = null;
    private Gallery showGallery = null;
    private Button unfoldButton = null;
    private TextView textView = null;
    private TextView titleTextView = null;

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.show);

        initView();
    }

    @Override
    protected void onResume()
    {
        // TODO Auto-generated method stu
        super.onResume();

        isFolded = true;
    }
    //初始化
    private void initView()
    {

        contents = new ArrayList<String>();

        File dir = new File(DIR);
        File[] files = dir.listFiles();

        for(int i=0; i<files.length; i++)
        {
            contents.add(DIR + files[i].getName());
        }

        layout = (FrameLayout)findViewById(R.id.layout);

        unfoldButton = (Button)findViewById(R.id.unfoldButton);
        unfoldButton.setOnClickListener(new UnfoldClickListener());

        showGallery = (Gallery)findViewById(R.id.showGallery);
        showGallery.setOnItemSelectedListener(new GalleryOnItemSelectedListener());
        showGallery.setAdapter(new ShowAdapter());

        titleTextView = (TextView)findViewById(R.id.titleTextView);
    }

    //滑动监听
    private class GalleryOnItemSelectedListener implements OnItemSelectedListener
    {
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
                long arg3)
        {
            // TODO Auto-generated method stub
            pos = arg2 + 1;

            titleTextView.setText("第" + pos +"个主题");
        }
        public void onNothingSelected(AdapterView<?> arg0)
        {
            // TODO Auto-generated method stub

        }

    }

    //按钮监听，展开一个透明的显示文本的遮挡层
    private class UnfoldClickListener implements OnClickListener
    {
        public void onClick(View v)
        {
            if(isFolded)
            {
                textView = new TextView(ShowActivity.this);

                textView.setTextColor(Color.BLUE);
                textView.setTextSize(20);
                textView.setText("滚滚长江东逝水，浪花淘尽英雄。/n" +
                        "是非成败转头空，/n" +
                        "青山依旧在，几度夕阳红。/n" +
                        "白发渔樵江渚上，惯看秋月春风。 /n" +
                        "一壶浊酒喜相逢，/n" +
                        "古今多少事，都付笑谈中。");
                textView.setGravity(Gravity.CENTER);
                textView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
                        ViewGroup.LayoutParams.FILL_PARENT));
                textView.setBackgroundColor(Color.parseColor("#86222222"));

                unfoldButton.setText("收回");

                isFolded = false;

                layout.addView(textView);
            }
            else
            {
                unfoldButton.setText("展开");

                isFolded = true;

                layout.removeView(textView);
            }
        }
    }

    private class ShowAdapter extends BaseAdapter
    {

        public int getCount()
        {
            // TODO Auto-generated method stub
            return contents.size();
        }
        public Object getItem(int position)
        {
            // TODO Auto-generated method stub
            return position;
        }
        public long getItemId(int position)
        {
            // TODO Auto-generated method stub
            return 0;
        }
        public View getView(int position, View convertView, ViewGroup parent)
        {
            // TODO Auto-generated method stub
            ImageView i = new ImageView(ShowActivity.this);

            Bitmap bm = BitmapFactory.decodeFile(contents.get(position));
//          i.setLayoutParams(new Gallery.LayoutParams(Gallery.LayoutParams.FILL_PARENT,
//                  Gallery.LayoutParams.FILL_PARENT));
            i.setScaleType(ImageView.ScaleType.FIT_XY);
            i.setImageBitmap(bm);

            return i;
        }
    }
}

效果如下：