Appium Page Object Model return Garbage Collected

I'm pretty new to Appium. I currently follow some video to create a POM Appium android testing. When i try to run the test, it throws this error:

java.lang.IllegalStateException: The element By.id: nameText is not locatable anymore because its context has been garbage collected

for more information, here I attached my Page Object class:

public class LoginPage extends AndroidGestures {
    
    AndroidDriver driver;
    
    public LoginPage(AndroidDriver driver) {
        super(driver);
        this.driver = driver;
        PageFactory.initElements(new AppiumFieldDecorator(driver), this);
    }
    
    @AndroidFindBy(id="com.androidsample.generalstore:id/nameField")
    private WebElement nameText;
    
    @AndroidFindBy(id="com.androidsample.generalstore:id/radioMale")
    private WebElement genderMale;
    
    @AndroidFindBy(id="com.androidsample.generalstore:id/radioFemale")
    private WebElement genderFemale;
    
    @AndroidFindBy(id="com.androidsample.generalstore:id/btnLetsShop")
    private WebElement loginButton;
    
    @AndroidFindBy(id="android:id/text1")
    private WebElement country;
    
    public void setName(String name) {
        nameText.sendKeys(name);
        driver.hideKeyboard();
    }
    
    public void setGender(String gender) {
        if(gender.toLowerCase().equals("female")) {
            genderFemale.click();
        } else if (gender.toLowerCase().equals("male")) {
            genderMale.click();
        }
    }
    
    public void selectCountry(String cntr) {
        country.click();
        scrollDownToTextAndClick(cntr);
    }
    
    public void login() {
        loginButton.click();
    }

}

Test class:

public class BasicStore extends BaseClass {
    
    LoginPage lgp = new LoginPage(driver);
    
    @Test (priority = 1, description = "Enter the general store")
    public void POM001() {
        
        // filling the form
        lgp.setName("Ayumi"); --> I assume this is where things go wrong
        lgp.setGender("female");
        lgp.selectCountry("Bahamas");
        lgp.login();
        
        threadSleep(3);
        
        // assert that we enter the correct page
        Boolean page = driver.findElement(AppiumBy.id("com.androidsample.generalstore:id/appbar_btn_cart")).isDisplayed();
            Assert.assertTrue(page);
    }
}

Some of the things i did try:

• [EDIT] Adding thread.sleep() to wait for the splash screen to finish
• [EDIT] using explicit wait for that element to be visible (10 seconds)
• Reinstall the apps from the emulator
• Creating a new virtual device with significantly bigger VM heap

As I've been looking around and haven't found anything related to this (or i was just too impatient), 2 questions pops out:

• What is main cause for this?
• As I saw from the Android studio device manager, seems that VM heap has things to do with Garbage Collection. If possible, given the apps is very simple, what is the recommended number of size for the VM heap, in regards of Appium testing?

Many thanks in advance for the time and answer!

In test class, try to put LoginPage lgp = new LoginPage(driver); inside the public void POM001() {}, then it should work

public class BasicStore extends BaseClass {
    @Test (priority = 1, description = "Enter the general store")
    public void POM001() {
        LoginPage lgp = new LoginPage(driver);
        // filling the form
        lgp.setName("Ayumi"); --> I assume this is where things go wrong
        lgp.setGender("female");
        lgp.selectCountry("Bahamas");
        lgp.login();
        
        threadSleep(3);
        
        // assert that we enter the correct page
        Boolean page = driver.findElement(AppiumBy.id("com.androidsample.generalstore:id/appbar_btn_cart")).isDisplayed();
            Assert.assertTrue(page);
    }
}