Dim Screen Android Firemonkey

Question

Does anyone know how to dim the screen on Delphi Firemonkey for Android? I've been googling around and searching but could only find how to remove the auto dim for android by acquiring a Wakelock (Delphi XE5 Android. How to use PowerManager.WakeLock?).

At best I'd like to achieve two states: Evening = 20% brightness Daytime = 100% brightness

I am using Delphi 10.1 Berlin. Thank you for your help.

Answer 1

Taking this Stack Overflow question, which has the Java solution, as a guide I rustled up this helper unit that should work in Delphi versions from around XE8 to 10.1 Berlin, which seems to do the trick:

unit ScreenBrightnessU;

interface

function GetScreenBrightness: Byte;
procedure SetScreenBrightness(Brightness: Byte);

implementation

uses
  MiscU,
  FMX.Helpers.Android,
{$IF RTLVersion >= 31}
  FMX.DialogService,
{$ELSE}
  FMX.Dialogs,
{$ENDIF}
  System.UITypes,
  System.SysUtils,
  Androidapi.Helpers,
  Androidapi.JNI.App,
  Androidapi.JNI.Provider,
  Androidapi.JNI.GraphicsContentViewText;

function GetScreenBrightness: Byte;
var
  Resolver: JContentResolver;
begin
  Resolver :=
{$IF RTLVersion >= 30}
    TAndroidHelper.ContentResolver;
{$ELSE}
    SharedActivityContext.getContentResolver;
{$ENDIF}
  Result := TJSettings_System.JavaClass.getInt(
    Resolver,
    TJSettings_System.JavaClass.SCREEN_BRIGHTNESS);
end;

procedure SetScreenBrightness(Brightness: Byte);
var
  Resolver: JContentResolver;
  AttainedBrightness: Single;
  LayoutParams: JWindowManager_LayoutParams;
  Window: JWindow;
begin
  if not HasPermission('android.permission.WRITE_SETTINGS') then
{$IF RTLVersion >= 31}
    TDialogService.MessageDialog('App does not have the WRITE_SETTINGS permission', TMsgDlgType.mtError, [TMsgDlgBtn.mbCancel], TMsgDlgBtn.mbCancel, 0, nil)
{$ELSE}
    MessageDlg('App does not have the WRITE_SETTINGS permission', TMsgDlgType.mtError, [TMsgDlgBtn.mbCancel], 0)
{$ENDIF}
  else
  begin
{$IF RTLVersion >= 30}
    Resolver := TAndroidHelper.ContentResolver;
{$ELSE}
    Resolver := SharedActivityContext.getContentResolver;
{$ENDIF}
    // This will set the manual mode (set the automatic mode off)
    TJSettings_System.JavaClass.putInt(
      Resolver,
      TJSettings_System.JavaClass.SCREEN_BRIGHTNESS_MODE,
      TJSettings_System.JavaClass.SCREEN_BRIGHTNESS_MODE_MANUAL);
    // This will set the required brightness
    TJSettings_System.JavaClass.putInt(
      Resolver,
      TJSettings_System.JavaClass.SCREEN_BRIGHTNESS,
      Brightness);
    try
      AttainedBrightness := GetScreenBrightness;
      CallInUIThread(
        procedure
        begin
  {$IF RTLVersion >= 30}
          Window := TAndroidHelper.Activity.getWindow;
  {$ELSE}
          Window := SharedActivity.getWindow;
  {$ENDIF}
          LayoutParams := Window.getAttributes;
          LayoutParams.screenBrightness := AttainedBrightness / 255;
          Window.setAttributes(LayoutParams);
        end);
    except
      // ONOES!!!!
      // <sweeps issue under the carpet>
    end;
  end;
end;

end.

You'll note that the code does permission checking via the helper unit below. This is not vital so long as you ensure you have the WRITE_SETTINGS permission set in your project for all the Android build configurations.

unit MiscU;

interface

function HasPermission(const Permission: string): Boolean;

implementation

uses
  FMX.Helpers.Android,
  Androidapi.Helpers,
  Androidapi.JNI.JavaTypes,
  Androidapi.JNI.GraphicsContentViewText;

function HasPermission(const Permission: string): Boolean;
begin
  //Permissions listed at http://d.android.com/reference/android/Manifest.permission.html
{$IF RTLVersion >= 30}
  Result := TAndroidHelper.Context.checkCallingOrSelfPermission(
{$ELSE}
  Result := SharedActivityContext.checkCallingOrSelfPermission(
{$ENDIF}
    StringToJString(Permission)) =
    TJPackageManager.JavaClass.PERMISSION_GRANTED
end;

end.