MAUI Blazor學習16-連續按BACK退出APP

SunnyTrudeau發表於2024-06-15
UIBlazorAPP

MAUI Blazor學習16-連續按BACK退出APP

MAUI Blazor系列目錄

  1. MAUI Blazor學習1-移動客戶端Shell佈局 - SunnyTrudeau - 部落格園 (cnblogs.com)
  2. MAUI Blazor學習2-建立移動客戶端Razor頁面 - SunnyTrudeau - 部落格園 (cnblogs.com)
  3. MAUI Blazor學習3-繪製ECharts圖表 - SunnyTrudeau - 部落格園 (cnblogs.com)
  4. MAUI Blazor學習4-繪製BootstrapBlazor.Chart圖表 - SunnyTrudeau - 部落格園 (cnblogs.com)
  5. MAUI Blazor學習5-BLE低功耗藍芽 - SunnyTrudeau - 部落格園 (cnblogs.com)
  6. MAUI Blazor學習6-掃描二維碼 - SunnyTrudeau - 部落格園 (cnblogs.com)
  7. MAUI Blazor學習7-實現登入跳轉頁面 - SunnyTrudeau - 部落格園 (cnblogs.com)
  8. MAUI Blazor學習8-支援多語言 - SunnyTrudeau - 部落格園 (cnblogs.com)
  9. MAUI Blazor學習9-VS Code開發除錯MAUI入門 - SunnyTrudeau - 部落格園 (cnblogs.com)
  10. MAUI Blazor學習10-BarcodeScanner掃描二維碼 - SunnyTrudeau - 部落格園 (cnblogs.com)
  11. MAUI Blazor學習11-百度地圖定位 - SunnyTrudeau - 部落格園 (cnblogs.com)
  12. MAUI Blazor學習12-檔案另存為 - SunnyTrudeau - 部落格園 (cnblogs.com)
  13. MAUI Blazor學習13-開啟檔案 - SunnyTrudeau - 部落格園 (cnblogs.com)
  14. MAUI Blazor學習14-選擇目錄 - SunnyTrudeau - 部落格園 (cnblogs.com)
  15. MAUI Blazor學習15-採用html2pdf.js生成pdf - SunnyTrudeau - 部落格園 (cnblogs.com)

安卓APP一般都是連續按2次BACK鍵退出，MAUI Blazor可以判斷當前導航頁面如果為最後一個，就啟動退出檢測。網上有現成的例程，照抄即可。參考https://blog.csdn.net/sD7O95O/article/details/132632457，《MAUI APP 釋出指南（三）vivo篇-CSDN部落格.mhtml》

在Platforms\Android\MainActivity.cs過載按鍵事件。

D:\Software\gitee\mauiblazorapp\MaBlaApp\Platforms\Android\MainActivity.cs

public class MainActivity : MauiAppCompatActivity
{
    private bool isExit = false;

    public override bool OnKeyDown([GeneratedEnum] Keycode keyCode, KeyEvent? e)
    {
        //最後一個頁面按BACK才觸發
        System.Diagnostics.Debug.WriteLine($"呼叫OnKeyDown, keyCode={keyCode} keyEvent={e}");

        if (keyCode == Keycode.Back)
        {
            var modelStack = Microsoft.Maui.Controls.Application.Current.MainPage.Navigation.ModalStack;
            if (modelStack.Count == 0)
            {
                if (isExit)
                {
                    //第2次返回鍵
                    Microsoft.Maui.Controls.Application.Current.Quit();
                }
                else
                {
                    //第一次返回鍵
                    isExit = true;
                    Task.Run(async () =>
                    {
                        await Task.Delay(2000);
                        isExit = false;
                    });
                    //用安卓的方法也可以
                    //new Android.OS.Handler().PostDelayed(() =>
                    //{
                    //    isExit = false;
                    //}, 2000);
                    Toast.MakeText(this, "再按一次退出", ToastLength.Long).Show();
                    return true;
                }
            }
        }

        return base.OnKeyDown(keyCode, e);
    }

    public override bool DispatchKeyEvent(KeyEvent? e)
    {
        //每次按BACK都觸發
        System.Diagnostics.Debug.WriteLine($"呼叫DispatchKeyEvent, keyEvent={e}");

        return base.DispatchKeyEvent(e);
    }
}

測試的時候發現點選BACK回退頁面時，觸發了2次DispatchKeyEvent，按下和彈起，但是沒有觸發OnKeyDown，直到退回到最後一頁，才會觸發OnKeyDown。

【正常回退頁面】

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95052961, downTime=95052961, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_UP, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95053063, downTime=95052961, deviceId=-1, source=0x101, displayId=0 }

【回退到最後一個頁面】

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95068879, downTime=95068879, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫OnKeyDown, keyCode=Back keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95068879, downTime=95068879, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_UP, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95069038, downTime=95068879, deviceId=-1, source=0x101, displayId=0 }

【回退到最後一個頁面，快速2次BACK退出APP】

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95094450, downTime=95094450, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫OnKeyDown, keyCode=Back keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95094450, downTime=95094450, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_UP, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95094575, downTime=95094450, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫DispatchKeyEvent, keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95095075, downTime=95095075, deviceId=-1, source=0x101, displayId=0 }

[0:] 呼叫OnKeyDown, keyCode=Back keyEvent=KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=0, metaState=0, flags=0x48, repeatCount=0, eventTime=95095075, downTime=95095075, deviceId=-1, source=0x101, displayId=0 }

DEMO程式碼地址：https://gitee.com/woodsun/mauiblazorapp

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