（七）android 通知对话框，并且监听了返回键，当按下返回键也会创建一个对话框

一、activity_main.java中代码

<LinearLayoutxmlns: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:gravity="center"
tools:context="com.example.Dialog.MainActivity">
<Button
android:onClick="click"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="对话框"/>
</LinearLayout>

二、MainActivity.java中的代码
1packagecom.example.Dialog;

importandroid.app.Activity;
importandroid.app.AlertDialog;
importandroid.app.AlertDialog.Builder;
importandroid.app.Dialog;
importandroid.content.DialogInterface;
importandroid.content.DialogInterface.OnClickListener;
importandroid.os.Bundle;
importandroid.view.KeyEvent;
importandroid.view.View;
importandroid.widget.Toast;

publicclassMainActivityextendsActivity{

@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}

publicvoidclick(Viewview){
AlertDialog.Builderbuilder=newBuilder(this);
builder.setTitle("提示");
builder.setIcon(R.drawable.ic_launcher);
builder.setMessage("是否要进行软件升级");
//builder.setCancelable(false);
builder.setPositiveButton("确定",newOnClickListener(){
@Override
publicvoidonClick(DialogInterfacedialog,intwhich){
//TODOAuto-generatedmethodstub
Toast.makeText(MainActivity.this,"确定被点击了",0).show();
}
});
builder.setNegativeButton("取消",newOnClickListener(){

@Override
publicvoidonClick(DialogInterfacedialog,intwhich){
//TODOAuto-generatedmethodstub
Toast.makeText(MainActivity.this,"取消被点击了",0).show();
}
});
builder.create().show();
}

@Override
publicbooleanonKeyDown(intkeyCode,KeyEventevent){
//TODOAuto-generatedmethodstub

if(keyCode==KeyEvent.KEYCODE_BACK){
AlertDialog.Builderbuilder=newBuilder(this);
builder.setTitle("提示");
builder.setMessage("确定要退出吗");
builder.create();
Dialogdialog;

builder.setPositiveButton("确定",newOnClickListener(){

@Override
publicvoidonClick(DialogInterfacedialog,intwhich){
//TODOAuto-generatedmethodstub
dialog.dismiss();
}
});
builder.setNegativeButton("取消",newOnClickListener(){

@Override
publicvoidonClick(DialogInterfacedialog,intwhich){
//TODOAuto-generatedmethodstub

}
});
dialog=builder.show();

}
returnfalse;
}
}