Einführung.md

+* Deklarative Definition
+* baut ein Modell auf für die Views
+
+## Kotlin Grundlagen für Jetpack Compose
+
+*(Receiver) Lambdas*
+```kotlin
+val receiverLambda: Number.() -> Unit = {
+    sqrt(toFloat())
+}
+
+val number = 2
+number.receiverLambda()
+```
+
+*Higher Order Functions*
+```kotlin
+fun myFunction(param: (Int) -> Int) = param(3)
+
+fun square(input: Int): Int = input.toDouble().pow(2.0).toInt()
+
+println(myFunction {
+    it.toDouble().pow(2.0).toInt()
+})
+
+println(myFunction(::square))
+```
+
+*Extension Functions*
+```kotlin
+fun String?.parseDate() = if (this == null) {
+    Date()
+} else {
+    SimpleDateFormat("yyyy-MM-dd")
+        .parse(this)
+}
+
+val String?.date: Date?
+    get() = if (this == null) {
+        Date()
+    } else {
+        SimpleDateFormat("yyyy-MM-dd")
+            .parse(this)
+    }
+```
+
+## Compose Grundlagen
+
+*Gradle Setup*
+
+```groovy
+android {
+    buildFeatures {
+        compose true
+    }
+    composeOptions {
+        kotlinCompilerExtensionVersion = "1.3.2"
+    }
+}
+
+dependencies {
+
+    implementation 'androidx.core:core-ktx:1.9.0'
+    implementation 'androidx.appcompat:appcompat:1.6.0'
+    def composeBom = platform('androidx.compose:compose-bom:2022.12.00')
+    implementation composeBom
+
+    // or Material Design 2
+//    implementation 'androidx.compose.material3:material3'
+    implementation 'androidx.compose.ui:ui'
+
+    // Android Studio Preview support
+    implementation 'androidx.compose.ui:ui-tooling-preview'
+    debugImplementation 'androidx.compose.ui:ui-tooling'
+
+    // Optional - Included automatically by material, only add when you need
+    // the icons but not the material library (e.g. when using Material3 or a
+    // custom design system based on Foundation)
+    implementation 'androidx.compose.material:material-icons-core'
+    // Optional - Add full set of material icons
+    implementation 'androidx.compose.material:material-icons-extended'
+
+    // Optional - Integration with activities
+    implementation 'androidx.activity:activity-compose:1.6.1'
+    // Optional - Integration with ViewModels
+    implementation 'androidx.lifecycle:lifecycle-viewmodel-compose:2.5.1'
+    // Optional - Integration with LiveData
+//    implementation 'androidx.compose.runtime:runtime-livedata'
+
+
+//    testImplementation 'junit:junit:4.13.2'
+//    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
+//    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
+//    androidTestImplementation 'androidx.compose.ui:ui-test-junit4'
+//    debugImplementation 'androidx.compose.ui:ui-test-manifest'
+}
+
+```
+
+* kotlin Version und Compose Compiler müssen zusammen passen! ( Bsp: kotlin 1.7.20 <-> Compose 1.3.2)
+* Später nähere Erklärung der Material Bibliotheken.
+
+*Compose in einer Activity*
+
+```kotlin
+class SampleActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        setContent {
+            /* Compose Content */
+        }
+    }
+}
+```
+
+*Definition eines Composables*
+
+```kotlin
+@Composable
+fun MyComposable() {
+    /* Compose Content */
+}
+```
+
+* Kann nur innerhalb von Composable Code aufgerufen werden.