Java 带按钮的 Android Eclipse 弹出消息

Android Eclipse Popup Message with Button

提问by user3212831

I would like to make it so, by a click of a button, there is a popup message.

我想让它这样，通过点击一个按钮，有一个弹出消息。

Right now the popup comes as soon as I open the app.

现在，只要我打开应用程序，就会弹出窗口。

BTW the button I want to trigger the popup is the about button in main.xml

顺便说一句，我想触发弹出的按钮是 main.xml 中的 about 按钮

Here is my main.xml (with the layout stuff):

这是我的 main.xml（带有布局内容）：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/main"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#3DE400"
    android:orientation="vertical" >

    <!-- background originally #d78a00 -->

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:fontFamily="sans-serif-condensed"
        android:paddingLeft="10dp"
        android:text="Sample App"
        android:textColor="#FFF"
        android:textSize="60sp" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="sans-serif-condensed"
        android:paddingLeft="10dp"
        android:text="@string/creator"
        android:textColor="#FFF"
        android:textSize="20dp" />

    <Button
        android:id="@+id/about"
        android:layout_width="123dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="50dp"
        android:background="@android:color/transparent"
        android:fontFamily="sans-serif-condensed"
        android:gravity="left"
        android:paddingLeft="10dp"
        android:text="@string/about"
        android:textColor="#FFF"
        android:textSize="40dp"
        android:onClick="show" />

</LinearLayout>

Here is my MainActivity.java:

这是我的 MainActivity.java：

package com.pranavsanghvi.sampleappv4;

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


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);
        alert.setTitle("About");
        alert.setMessage("Sample About");
        alert.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick (DialogInterface dialog, int id) {
                Toast.makeText (MainActivity.this, "Success", Toast.LENGTH_SHORT) .show();
            }
        });
        alert.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(MainActivity.this, "Fail", Toast.LENGTH_SHORT) .show();
            }
        });
        alert.show();


    }   
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

回答by Rohan Kandwal

If you want to show popup on about button click add the following in onCreate()

如果要在关于按钮上显示弹出窗口，请单击添加以下内容 onCreate()

Button aboutButton = (Button) findViewById(R.id.about);
aboutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                alert.show();
            }
        });

just remove alert.show();from onCreate();

只需alert.show();从 onCreate() 中删除；

update :-

更新 ：-

Are you getting alert can't be resolved? If so then either make alert global i.e. declare it outside onCreate()

您是否收到警报无法解决？如果是这样，要么使警报成为全球性的，即在外面声明它onCreate()

public class MainActivity extends Activity {
    AlertDialog.Builder alert;
@Override
    protected void onCreate(Bundle savedInstanceState) {
// code
alert = new AlertDialog.Builder(MainActivity.this);
// code

or make it final so that it is

或使其最终成为

final AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);

also remove alert.show();which is in onCreate();

也删除alert.show();哪个在onCreate();

回答by Melquiades

First, declare your alert and button in MainActivity:

首先，在 MainActivity 中声明您的警报和按钮：

public class Mainactivity extends Activity {
    private AlertDialog.Builder alert;
    private Button btAbout;

    //rest of the code
}

Then, in onCreate(), create your alert as you did, except this line:

然后，在 onCreate() 中，像您一样创建警报，除了这一行：

alert.show();    // <--- remove this line as not to show the alert immediately

Because you've declared global alert, remember to also remove AlertDialog.Builder here, so instead of:

因为你已经声明了全局警报，记得在这里也删除 AlertDialog.Builder，而不是：

AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);
alert.setTitle("About");

//rest of the code

you should have:

你应该有：

alert = new AlertDialog.Builder(MainActivity.this);
alert.setTitle("About");

//rest of the code

Next, get the handle to your about button:

接下来，获取关于按钮的句柄：

btAbout = (Button) findViewById(R.id.about);

Set onClickListener to button:

将 onClickListener 设置为按钮：

btAbout.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        //when this button is clicked, show the alert
        alert.show();
    }
});

All of this is in onCreate(). Now when button is clicked, your alert will be displayed.

所有这些都在 onCreate() 中。现在，当单击按钮时，将显示您的警报。