use observeView instead of old approach

Author: ajungg

java-sample/src/main/java/io/snabble/testapp/BaseActivity.java

@@ -1,38 +1,21 @@
 package io.snabble.testapp;
 
-import android.app.Activity;
-import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.KeyEvent;
 import android.view.View;
 import android.widget.ProgressBar;
 import android.widget.TextView;
-
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.fragment.app.Fragment;
-
-import io.snabble.sdk.Snabble;
 import io.snabble.sdk.codes.ScannedCode;
 import io.snabble.sdk.ui.SnabbleUI;
 import io.snabble.sdk.ui.cart.ShoppingCartActivity;
-import io.snabble.sdk.ui.checkout.CheckoutActivity;
-import io.snabble.sdk.ui.payment.AgeVerificationInputActivity;
-import io.snabble.sdk.ui.payment.CreditCardInputActivity;
-import io.snabble.sdk.ui.payment.PaydirektInputActivity;
 import io.snabble.sdk.ui.payment.PaymentCredentialsListActivity;
 import io.snabble.sdk.ui.payment.PaymentOptionsActivity;
-import io.snabble.sdk.ui.payment.PayoneInputActivity;
-import io.snabble.sdk.ui.payment.ProjectPaymentOptionsActivity;
-import io.snabble.sdk.ui.payment.SEPACardInputActivity;
 import io.snabble.sdk.ui.scanner.SelfScanningActivity;
-import io.snabble.sdk.ui.search.ProductSearchActivity;
 import io.snabble.sdk.ui.utils.ZebraSupport;
 import io.snabble.sdk.ui.scanner.ProductResolver;
-import kotlin.Unit;
-import kotlin.jvm.functions.Function2;
 
 public abstract class BaseActivity extends AppCompatActivity {
 

ui/src/main/java/io/snabble/sdk/ui/cart/CheckoutBar.kt

@@ -37,7 +37,7 @@ import io.snabble.sdk.utils.Logger
 
 open class CheckoutBar @JvmOverloads constructor(
     context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
-) : LinearLayout(context, attrs, defStyleAttr), Checkout.OnCheckoutStateChangedListener {
+) : LinearLayout(context, attrs, defStyleAttr) {
     init {
         inflate(getContext(), R.layout.snabble_view_checkout_bar, this)
     }
@@ -126,19 +126,9 @@ open class CheckoutBar @JvmOverloads constructor(
             false
         })
 
-        context.requireFragmentActivity().lifecycle.addObserver(object : LifecycleObserver {
-            @OnLifecycleEvent(Lifecycle.Event.ON_START)
-            fun onStart() {
-                if (isAttachedToWindow) {
-                    registerListeners()
-                }
-            }
-
-            @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
-            fun onStop() {
-                unregisterListeners()
-            }
-        })
+        project.checkout.checkoutState.observeView(this) {
+            onStateChanged(it)
+        }
     }
 
     private fun handleButtonClick() {
@@ -266,28 +256,7 @@ open class CheckoutBar @JvmOverloads constructor(
         }
     }
 
-    private fun registerListeners() {
-        project.checkout.addOnCheckoutStateChangedListener(this)
-    }
-
-    private fun unregisterListeners() {
-        project.checkout.removeOnCheckoutStateChangedListener(this)
-        progressDialog.dismiss()
-    }
-
-    override fun onAttachedToWindow() {
-        super.onAttachedToWindow()
-        if (!isInEditMode) {
-            registerListeners()
-        }
-    }
-
-    override fun onDetachedFromWindow() {
-        super.onDetachedFromWindow()
-        unregisterListeners()
-    }
-
-    override fun onStateChanged(state: Checkout.State) {
+    protected fun onStateChanged(state: Checkout.State) {
         when (state) {
             Checkout.State.HANDSHAKING -> {
                 progressDialog.showAfterDelay(300)
@@ -344,7 +313,6 @@ open class CheckoutBar @JvmOverloads constructor(
                     putString(CheckoutActivity.ARG_PROJECT_ID, project.id)
                 })
                 progressDialog.dismiss()
-                unregisterListeners()
             }
             Checkout.State.INVALID_PRODUCTS -> {
                 val invalidProducts = project.checkout.invalidProducts