Android AlertDialog 示例

Android AlertDialog 可以用来显示带有确定和取消按钮的对话框消息。可以用来中断并询问用户是否选择继续或中止。

Android AlertDialog由三个区域组成：标题，内容区域和动作按钮。

Android AlertDialog是Dialog类的子类。

AlertDialog类的方法

Android AlertDialog示例

让我们看一个简单的Android AlertDialog示例。

activity_main.xml

您可以拥有多个组件，这里我们只有一个文本视图。

<?xml version="1.0" encoding="utf-8"?>  
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:app="http://schemas.android.com/apk/res-auto"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    tools:context="example.javatpoint.com.alertdialog.MainActivity">  

    <Button  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:id="@+id/button"  
        android:text="Close app"  
        app:layout_constraintBottom_toBottomOf="parent"  
        app:layout_constraintLeft_toLeftOf="parent"  
        app:layout_constraintRight_toRightOf="parent"  
        app:layout_constraintTop_toTopOf="parent" />  

</android.support.constraint.ConstraintLayout> 

strings.xml

<resources>  
    <string name="app_name">AlertDialog</string>  
    <string name="dialog_message">Welcome to Alert Dialog</string>  
    <string name="dialog_title">Javatpoint Alert Dialog</string>  
</resources>  

Activity类

让我们编写代码来创建并显示AlertDialog。

package example.javatpoint.com.alertdialog;

import android.content.DialogInterface;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.app.AlertDialog;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    Button closeButton;
    AlertDialog.Builder builder;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        closeButton = (Button) findViewById(R.id.button);
        builder = new AlertDialog.Builder(this);
        closeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //Uncomment the below code to Set the message and title from the strings.xml file
                builder.setMessage(R.string.dialog_message) .setTitle(R.string.dialog_title);

                //Setting message manually and performing action on button click
                builder.setMessage("Do you want to close this application ?")
                        .setCancelable(false)
                        .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                finish();
                                Toast.makeText(getApplicationContext(),"you choose yes action for alertbox",
                                Toast.LENGTH_SHORT).show();
                            }
                        })
                        .setNegativeButton("No", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                //  Action for 'NO' Button
                                dialog.cancel();
                                Toast.makeText(getApplicationContext(),"you choose no action for alertbox",
                                Toast.LENGTH_SHORT).show();
                            }
                        });
                //Creating dialog box
                AlertDialog alert = builder.create();
                //Setting the title manually
                alert.setTitle("AlertDialogExample");
                alert.show();
            }
        });
    }
}

输出：