实现遮罩层效果

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实现的就是在最上层显示动态悬浮的说明，比如在程序中，在最上层显示一个说明的文字。实现的原理也很简单，就是在最上层需要显示的设置为透明或者半透明状态，然后就是布局的设计。

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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;
}
}
}</i>