大家好今天我們繼續來示範Dialog的其他用法，在這我們開一個新的空白專案來示範，首先一樣先上程式碼。

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">


    <Button
        android:id="@+id/btnSingleListDialog"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SingleListDialog"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnMultipleListDialog"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="MultipleListDialog"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btnSingleListDialog" />


</androidx.constraintlayout.widget.ConstraintLayout>

在xml新增了兩個按鈕，它們的功能分別是：
1.在很多個選項裡面選取一個項目，然後再按確定做下一個動作。
2.在很多個選項中可以選取多個項目，然後按下確定做下一個動作。

###MainActivity:

package com.example.day30_dialog_2;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button mShowSingleChoiceDialog;
    private Button mShowMultipleChoiceDialog;
    int SingleCount = -1;

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

    private void init() {
        mShowSingleChoiceDialog =findViewById(R.id.btnSingleListDialog);
        mShowMultipleChoiceDialog =findViewById(R.id.btnMultipleListDialog);
        mShowSingleChoiceDialog.setOnClickListener(this);
        mShowMultipleChoiceDialog.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btnSingleListDialog:
                showSingleChoice();
                break;
            case R.id.btnMultipleListDialog:
                showMultipleChoice();
                break;
        }
    }

    private void showMultipleChoice() {
        final String[] english = {"A","B","C","D","E","F","G"};
        final boolean[] select = new boolean[english.length];
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("複選的List")
                .setMultiChoiceItems(english, select, new DialogInterface.OnMultiChoiceClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which, boolean isChecked) {

                    }
                })
                .setPositiveButton("確定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String result = "你選擇了:";
                        for (int i=0;i<select.length;i++){
                            if (select[i]){
                                result = result + "," + english[i];
                            }
                        }
                        Toast.makeText(MainActivity.this,result,Toast.LENGTH_SHORT).show();
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                })
                .create()
                .show();
    }

    private void showSingleChoice() {
        SingleCount = -1;
        final String[] english = {"A","B","C","D","E","F","G"};
        AlertDialog.Builder builder = new AlertDialog.Builder(this);

        builder.setTitle("單選的List")
                .setSingleChoiceItems(english, -1, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        SingleCount = which;
                    }
                })
                .setPositiveButton("確定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        if (SingleCount == -1){
                            Toast.makeText(MainActivity.this,"選取失敗，請重新選取",Toast.LENGTH_SHORT).show();
                        }else {
                            Toast.makeText(MainActivity.this,"你選擇的是:"+english[SingleCount],Toast.LENGTH_SHORT).show();
                        }
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                })
                .create()
                .show();
    }
}

我們來看看當按鈕按下去會做的動作的function:
1.showSingleChoice():

private void showSingleChoice() {
        SingleCount = -1;
        final String[] english = {"A","B","C","D","E","F","G"};
        AlertDialog.Builder builder = new AlertDialog.Builder(this);

        builder.setTitle("單選的List")
                .setSingleChoiceItems(english, -1, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        SingleCount = which;
                    }
                })
                .setPositiveButton("確定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        if (SingleCount == -1){
                            Toast.makeText(MainActivity.this,"選取失敗，請重新選取",Toast.LENGTH_SHORT).show();
                        }else {
                            Toast.makeText(MainActivity.this,"你選擇的是:"+english[SingleCount],Toast.LENGTH_SHORT).show();
                        }
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                })
                .create()
                .show();
    }

首先我們先設定一個陣列並且將我們要的資料放進去裡面，然後在.setSingleChoiceItems裡面放入陣列，在english逗號的旁邊設置-1是當我點擊單選的按鈕時，他會跳出完全沒有選取任何選項的Dialog，反之若我將它設定成1時，在一開始我點擊了單選的按鈕時，明明我還沒選擇任何選項，但是選項B已經被選取了，所以我將它預設為-1。

public void onClick(DialogInterface dialog, int which) {
                        SingleCount = which;
                    }

在一開始想必有些人會問為什麼要宣告一個int變數SingleCount等於-1，由上面的程式碼我們可以知道int which是代表我們點選到項目，我們使SingleCount等於which然後再Dialog按下確定按鈕時從SingleCount得知我們選擇的項目是多少，然後再使用Toast來讓使用者了解到他們選擇的項目是多少，最後再做一個防呆功能，這樣一個簡單的單選Dialog就完成了。

結果如下:

接下來繼續介紹再多個選項當中選取多個選項

private void showMultipleChoice() {
        final String[] english = {"A","B","C","D","E","F","G"};
        final boolean[] select = new boolean[english.length];
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("複選的List")
                .setMultiChoiceItems(english, select, new DialogInterface.OnMultiChoiceClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which, boolean isChecked) {

                    }
                })
                .setPositiveButton("確定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String result = "你選擇了:";
                        for (int i=0;i<select.length;i++){
                            if (select[i]){
                                result = result + "," + english[i];
                            }
                        }
                        Toast.makeText(MainActivity.this,result,Toast.LENGTH_SHORT).show();
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                })
                .create()
                .show();
    }

在這和前一個Dialog差不多，先建立一個陣列將資料放進去，和上一個不同的是.setSingleChoiceItems變成了使用.setMultiChoiceItems，完成後結果如下:

今天就介紹到這，明天再繼續介紹其他的用法