Add custom View PieChartView.kt. It show a cost by Category

app/src/main/java/otus/homework/customview/ColorSet.kt

@@ -0,0 +1,14 @@
+package otus.homework.customview
+
+enum class ColorSet(val hexCode: String) {
+    PRIMARY("#123456"),
+    RED("#FFFF0000"),
+    GREEN("#00FF00"),
+    BLUE("#0000FF"),
+    YELLOW("#FFFF00"),
+    ORANGE("#FFA500"),
+    PURPLE("#800080"),
+    PINK("#FFC0CB"),
+    CYAN("#00FFFF"),
+    BROWN("#79553D")
+}

app/src/main/java/otus/homework/customview/MainActivity.kt

@@ -1,11 +1,45 @@
 package otus.homework.customview
 
-import androidx.appcompat.app.AppCompatActivity
+import android.content.Context
 import android.os.Bundle
+import android.util.Log
+import android.widget.Toast
+import androidx.appcompat.app.AppCompatActivity
+import com.google.gson.Gson
+import com.google.gson.reflect.TypeToken
+import otus.homework.customview.databinding.ActivityMainBinding
 
 class MainActivity : AppCompatActivity() {
+    private lateinit var binding: ActivityMainBinding
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
+        binding = ActivityMainBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        val testPayData = parseJson(this, R.raw.payload)
+        for (item in testPayData) {
+            Log.d("MainActivity", item.toString())
+        }
+        val categories = testPayData.groupBy { it.category }
+        Log.d("MainActivity", "countCategories: $categories")
+        for (it in categories) {
+            val amount = it.value.sumOf { it.amount }
+            Log.d("MainActivity", "category: ${it.key}" + " amount: $amount")
+        }
+
+        binding.pieChartView.setData(testPayData)
+        binding.pieChartView.setOnCategoryClickListener { category ->
+            Toast.makeText(this, category, Toast.LENGTH_SHORT).show()
+            Log.d("MainActivity", "category1: $category")
+        }
+    }
+
+    private fun parseJson(context: Context, resId: Int): List<PieChartData> {
+        context.resources.openRawResource(resId).use { inputStream ->
+            val json = inputStream.bufferedReader().readText()
+            val type = object : TypeToken<List<PieChartData>>() {}.type
+            return Gson().fromJson(json, type)
+        }
     }
 }

app/src/main/java/otus/homework/customview/PieChartData.kt

@@ -0,0 +1,3 @@
+package otus.homework.customview
+
+data class PieChartData(val id: Int, val name: String, val amount: Int, val category: String, val time: Long)

app/src/main/java/otus/homework/customview/PieChartView.kt

@@ -0,0 +1,215 @@
+package otus.homework.customview
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.Paint
+import android.graphics.Path
+import android.graphics.RectF
+import android.os.Bundle
+import android.os.Parcelable
+import android.util.AttributeSet
+import android.util.Log
+import android.view.MotionEvent
+import android.view.View
+import androidx.core.graphics.toColorInt
+import kotlin.enums.EnumEntries
+import kotlin.enums.enumEntries
+import kotlin.math.atan2
+import kotlin.math.sqrt
+
+class PieChartView @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null
+) : View(context, attrs) {
+    private var pieHeight: Float = height / 2f
+    private var pieWidth: Float = width / 2f
+    private var payChartData: List<PieChartData> = emptyList()
+    private var totalAmount: Int = 0
+    private var colorSet: EnumEntries<ColorSet> = enumEntries<ColorSet>()
+    private var pieElements: MutableList<PieElement> = mutableListOf()
+
+    private var paint: Paint = Paint()
+    private val paintText: Paint = Paint()
+    private var rect: RectF = RectF()
+    private var selectedCategory: String? = null
+    private var onCategoryClickListener: ((String) -> Unit)? = null
+    private val path: Path = Path()
+
+    fun setOnCategoryClickListener(listener: (String) -> Unit) {
+        onCategoryClickListener = listener
+    }
+
+    fun setData(data: List<PieChartData>) {
+        payChartData = data
+        initPieElements()
+    }
+
+    init {
+        paintText.color = Color.BLACK
+        paintText.textSize = 30f
+        paintText.textAlign = Paint.Align.CENTER
+    }
+
+    private fun initPieElements() {
+        val categories = payChartData.groupBy { it.category }
+        totalAmount = payChartData.sumOf { it.amount }
+        var counter = 0
+        var startAngle = 0f
+        pieElements.clear()
+        for (it in categories) {
+            val categoryAmount = it.value.sumOf { it.amount }
+            val partSize = categoryAmount / (totalAmount * 1f)
+            val angle = partSize * 360f
+            pieElements.add(
+                PieElement(
+                    colorSet[counter],
+                    startAngle,
+                    angle,
+                    it.key,
+                    categoryAmount
+                )
+            )
+            counter++
+            startAngle += angle
+        }
+    }
+
+    data class PieElement(
+        val color: ColorSet,
+        val startAngle: Float,
+        val angle: Float,
+        val category: String,
+        val amount: Int
+    )
+
+    override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        val radius = maxOf(pieHeight, pieWidth) / 2.0f
+
+        rect.set(
+            pieWidth - radius,
+            pieHeight - radius,
+            pieWidth + radius,
+            pieHeight + radius
+        )
+        for (item in pieElements) {
+            drawPieElement(canvas, getPiePaint(paint, item), rect, item)
+            if (item.category == selectedCategory) {
+                drawPieElement(canvas, getSelectPiePaint(), rect, item)
+                canvas.drawText(
+                    "${item.category}: ${item.amount} руб",
+                    pieWidth,
+                    pieHeight - 1.7f * radius,
+                    paintText
+                )
+            }
+        }
+    }
+
+    fun getPiePaint(paint: Paint, pieElement: PieElement): Paint {
+        paint.reset()
+
+        paint.color = pieElement.color.hexCode.toColorInt()
+        if (pieElement.category == selectedCategory) {
+            paint.alpha = 255
+        } else {
+            paint.alpha = 127
+        }
+        paint.style = Paint.Style.FILL_AND_STROKE
+        return paint
+    }
+
+    fun getSelectPiePaint(): Paint {
+        paint.reset()
+        paint.style = Paint.Style.STROKE
+        paint.strokeWidth = 2f
+        paint.color = Color.BLACK
+        paint.strokeJoin = Paint.Join.BEVEL
+        return paint
+    }
+
+    fun drawPieElement(
+        canvas: Canvas,
+        paint: Paint,
+        rect: RectF,
+        pieElement: PieElement
+    ) {
+        path.reset()
+        path.addArc(rect, pieElement.startAngle, pieElement.angle)
+        canvas.drawArc(rect, pieElement.startAngle, pieElement.angle, true, paint)
+        canvas.drawTextOnPath(pieElement.angle.toUInt().toString() + "%", path, 0f, 0f, paintText)
+    }
+
+    @SuppressLint("ClickableViewAccessibility")
+    override fun onTouchEvent(event: MotionEvent): Boolean {
+        if (event.action == MotionEvent.ACTION_DOWN) {
+            val midHeight = height / 2f
+            val midWidth = width / 2f
+            val dx = event.x - midWidth
+            val dy = event.y - midHeight
+            val dist = sqrt(dx * dx + dy * dy)
+
+            val radius = maxOf(midHeight, midWidth) / 2.0f
+            val innerRadius = radius - radius / 2
+            val outerRadius = radius + radius / 2
+
+            if (dist in innerRadius..outerRadius) {
+                val touchAngle = (Math.toDegrees(atan2(dy.toDouble(), dx.toDouble())) + 360) % 360
+                val slice = pieElements.firstOrNull {
+                    touchAngle in it.startAngle..(it.startAngle + it.angle)
+                }
+                slice?.let {
+                    selectedCategory = it.category
+                    onCategoryClickListener?.invoke(it.category)
+                    Log.d("${javaClass.name}", "category: $selectedCategory")
+                    invalidate()
+                }
+            }
+        }
+        return super.onTouchEvent(event)
+    }
+
+    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
+        super.onSizeChanged(w, h, oldw, oldh)
+        pieHeight = height / 2f
+        pieWidth = width / 2f
+    }
+
+    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
+        // Explicit width measurement example
+        val widthMode = MeasureSpec.getMode(widthMeasureSpec)
+        val widthSize = MeasureSpec.getSize(widthMeasureSpec)
+
+        val desiredWidth = (resources.displayMetrics.density * 360).toInt()
+
+        val width = when (widthMode) {
+            MeasureSpec.EXACTLY -> widthSize
+            MeasureSpec.AT_MOST -> minOf(desiredWidth, widthSize)
+            MeasureSpec.UNSPECIFIED -> desiredWidth
+            else -> Log.w("${javaClass.name}", "Unknown MeasureSpec")
+        }
+
+        // Simplified height measurement example
+        val minHeight = suggestedMinimumHeight + paddingTop + paddingBottom
+
+        // Combined result
+        setMeasuredDimension(width, resolveSize(minHeight, heightMeasureSpec))
+    }
+
+    override fun onSaveInstanceState(): Parcelable {
+        return Bundle().apply {
+            putParcelable("super", super.onSaveInstanceState())
+            putString("selectedCategory", selectedCategory)
+        }
+    }
+
+    override fun onRestoreInstanceState(state: Parcelable?) {
+        (state as? Bundle)?.let {
+            selectedCategory = it.getString("selectedCategory", null)
+            super.onRestoreInstanceState(it.getParcelable("super"))
+        }
+    }
+}

app/src/main/res/layout/activity_main.xml

@@ -10,10 +10,21 @@
     <TextView
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
+        android:text="@string/Title"
+        app:layout_constraintBottom_toTopOf="@+id/pieChartView"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        />
+
+    <otus.homework.customview.PieChartView
+        android:id="@+id/pieChartView"
+        android:layout_width="380dp"
+        android:layout_height="450dp"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintRight_toRightOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"/>
 
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/strings.xml

@@ -1,3 +1,4 @@
 <resources>
     <string name="app_name">Custom View</string>
+    <string name="Title">Траты по категориям</string>
 </resources>