實現透明的對話框

我們可以通過修改對話框佈局參數的 alpha 屬性, 實現透明的對話框.
WindowManager.LayoutParams params = dialog.getWindow().getAttributes();
params.alpha = 0.6f;
dialog.getWindow().setAttributes(params);

package com.TransparentDialog;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;

public class TransparentDialogActivity extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      Button buttonStartDialog = (Button)findViewById(R.id.start);
      buttonStartDialog.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    //Create AlertDialog
    AlertDialog.Builder myAlertDialog = new AlertDialog.Builder(TransparentDialogActivity.this);
    myAlertDialog.setTitle("--- Title ---");
    
    myAlertDialog.setMessage("Alert Dialog Message");
    
    myAlertDialog.setPositiveButton("OK", new DialogInterface.OnClickListener() {
     // do something when the button is clicked
     public void onClick(DialogInterface arg0, int arg1) {
      //... 
     }});
    
    myAlertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
     // do something when the button is clicked
     public void onClick(DialogInterface arg0, int arg1) {
      //... 
     }});
    
    AlertDialog dialog = myAlertDialog.show();
    
    WindowManager.LayoutParams params = dialog.getWindow().getAttributes();
    params.alpha = 0.6f;
    dialog.getWindow().setAttributes(params);
   }});
  }
   
}

<?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:orientation="vertical" >

  <Button
      android:id="@+id/start"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:text="- Start -" />
  <ImageView
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:src="@drawable/ic_launcher"/>

</LinearLayout>