一、返回键实现对话框弹出是否退出应用程序

package com.example.a;

 

import android.os.Bundle;

import android.app.Activity;

import android.app.AlertDialog;

import android.app.AliasActivity;

import android.app.Dialog;

import android.content.DialogInterface;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

 

public class MainActivity extends Activity {

 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

 

 

  public void onBackPressed(){

  AlertDialog dialog;

   AlertDialog.Builder builder = new AlertDialog.Builder(this)

   .setIcon(R.drawable.ic_launcher)

   .setTitle("asd")

   .setMessage("sadsads")

   .setPositiveButton("quedig", new DialogInterface.OnClickListener() {

 

@Override

public void onClick(DialogInterface dialog, int which) {

// TODO Auto-generated method stub

dialog.dismiss();

MainActivity.this.finish();

}

 

 

})

   .setNegativeButton("quxiao", new DialogInterface.OnClickListener() {

 

@Override

public void onClick(DialogInterface dialog, int which) {

// TODO Auto-generated method stub

dialog.dismiss();

}

});

   dialog=builder.create();

   dialog.show();

  }

  

   

    

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

 

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world" />

 

</RelativeLayout>

 

 

 

二、实现以下场景：从一个activity中点击一个按钮后，弹出一个单选按钮对话框，上面有“男”“女”两个选项，选定后，TOAST弹出 你选择了男，或你选择了女（参考书上改字体）

package com.example.a;

 

import android.os.Bundle;

import android.app.Activity;

import android.app.AlertDialog;

import android.app.AliasActivity;

import android.app.Dialog;

import android.content.DialogInterface;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

 

public class MainActivity extends Activity {

 

Button btn;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        

    }

 

 

  public void onclick(View v){

  AlertDialog dialog;

   AlertDialog.Builder builder = new AlertDialog.Builder(this)

   .setIcon(R.drawable.ic_launcher)

   .setTitle("选择")

   .setMessage("选择男女")

   .setPositiveButton("nan", new DialogInterface.OnClickListener() {

 

@Override

public void onClick(DialogInterface dialog, int which) {

// TODO Auto-generated method stub

Toast.makeText(MainActivity.this, "你选择了男", 10).show();

dialog.dismiss();

 

}

 

 

})

   .setNegativeButton("nv", new DialogInterface.OnClickListener() {

 

@Override

public void onClick(DialogInterface dialog, int which) {

// TODO Auto-generated method stub

Toast.makeText(MainActivity.this, "你选择了女", 10).show();

dialog.dismiss();

}

});

   dialog=builder.create();

   dialog.show();

  }

  

   

    

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

 

    <Button 

        

        android:layout_height="match_parent"

        android:layout_width="match_parent"

        android:text="按钮"

        android:onClick="onclick"

        />

 

</RelativeLayout>

 

 

 

3. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" 

    android:orientation="vertical">

 

    <TextView 

        android:layout_height="100dp"

        android:layout_width="match_parent"

        android:text="1.显示文本信息"

        />

    <Button 

        

        android:layout_height="100dp"

        android:layout_width="100dp"

        android:text="2.按钮"

        android:onClick="onclick"

        />

    <EditText 

        android:layout_height="100dp"

        android:layout_width="match_parent"

        android:hint="3.输入文本信息"

        />

    <RadioGroup 

        android:layout_height="wrap_content"

        android:layout_width="wrap_content"

        android:orientation="horizontal">

        <RadioButton 

            android:layout_height="wrap_content"

        android:layout_width="wrap_content"

        android:text="nan"/>

        <RadioButton 

            android:layout_height="wrap_content"

        android:layout_width="wrap_content"

        android:text="nv"/>

        

    </RadioGroup>

    <CheckBox 

       android:layout_height="wrap_content"

        android:layout_width="wrap_content"

        android:text="DIANNAO"/>

     <CheckBox 

       android:layout_height="wrap_content"

        android:layout_width="wrap_content"

        android:text="SHOUJI"/>

 

</LinearLayout>