Draw polygons on a map

This example draws polygons of various shapes and colors on a map.

For more information, see the documentation.

Get started

Before you can try the sample code, you must configure your development environment. For more information, see Maps SDK for Android code samples.

View the code

Kotlin

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.polygon_demo)

    fillHueBar = findViewById<SeekBar>(R.id.fillHueSeekBar).apply {
        max = MAX_HUE_DEGREES
        progress = MAX_HUE_DEGREES / 2
    }

    fillAlphaBar = findViewById<SeekBar>(R.id.fillAlphaSeekBar).apply {
        max = MAX_ALPHA
        progress = MAX_ALPHA / 2
    }

    strokeWidthBar = findViewById<SeekBar>(R.id.strokeWidthSeekBar).apply {
        max = MAX_WIDTH_PX
        progress = MAX_WIDTH_PX / 3
    }

    strokeHueBar = findViewById<SeekBar>(R.id.strokeHueSeekBar).apply {
        max = MAX_HUE_DEGREES
        progress = 0
    }

    strokeAlphaBar = findViewById<SeekBar>(R.id.strokeAlphaSeekBar).apply {
        max = MAX_ALPHA
        progress = MAX_ALPHA
    }

    strokeJointTypeSpinner = findViewById<Spinner>(R.id.strokeJointTypeSpinner).apply {
        adapter = ArrayAdapter(
                this@PolygonDemoActivity, android.R.layout.simple_spinner_item,
                getResourceStrings(jointTypeNameResourceIds))
    }

    strokePatternSpinner = findViewById<Spinner>(R.id.strokePatternSpinner).apply {
        adapter = ArrayAdapter(
                this@PolygonDemoActivity, android.R.layout.simple_spinner_item,
                getResourceStrings(patternTypeNameResourceIds))
    }

    clickabilityCheckbox = findViewById(R.id.toggleClickability)

    val mapFragment = supportFragmentManager.findFragmentById(R.id.map) as SupportMapFragment
    mapFragment.getMapAsync(this)
}

override fun onMapReady(googleMap: GoogleMap) {

    // return early if the map was not initialised properly
    googleMap ?: return

    val fillColorArgb = Color.HSVToColor(
            fillAlphaBar.progress, floatArrayOf(fillHueBar.progress.toFloat(), 1f, 1f))
    val strokeColorArgb = Color.HSVToColor(
            strokeAlphaBar.progress, floatArrayOf(strokeHueBar.progress.toFloat(), 1f, 1f))

    with(googleMap) {
        // Override the default content description on the view, for accessibility mode.
        setContentDescription(getString(R.string.polygon_demo_description))
        // Move the googleMap so that it is centered on the mutable polygon.
        moveCamera(CameraUpdateFactory.newLatLngZoom(center, 4f))

        // Create a rectangle with two rectangular holes.
        mutablePolygon = addPolygon(PolygonOptions().apply {
            addAll(createRectangle(center, 5.0, 5.0))
            addHole(createRectangle(LatLng(-22.0, 128.0), 1.0, 1.0))
            addHole(createRectangle(LatLng(-18.0, 133.0), 0.5, 1.5))
            fillColor(fillColorArgb)
            strokeColor(strokeColorArgb)
            strokeWidth(strokeWidthBar.progress.toFloat())
            clickable(clickabilityCheckbox.isChecked)
        })

        // Add a listener for polygon clicks that changes the clicked polygon's stroke color.
        setOnPolygonClickListener { polygon ->
            // Flip the red, green and blue components of the polygon's stroke color.
            polygon.strokeColor = polygon.strokeColor xor 0x00ffffff
        }
    }

    // set listeners on seekBars
    arrayOf(fillHueBar, fillAlphaBar, strokeWidthBar, strokeHueBar, strokeAlphaBar).map {
        it.setOnSeekBarChangeListener(this)
    }

    // set listeners on spinners
    arrayOf(strokeJointTypeSpinner, strokePatternSpinner).map {
        it.onItemSelectedListener = this
    }

    // set line pattern and joint type based on current spinner position
    with(mutablePolygon) {
        strokeJointType = getSelectedJointType(strokeJointTypeSpinner.selectedItemPosition)
        strokePattern = getSelectedPattern(strokePatternSpinner.selectedItemPosition)
    }

}
PolygonDemoActivity.kt

Java

public class PolygonDemoActivity extends AppCompatActivity
        implements OnSeekBarChangeListener, OnItemSelectedListener, OnMapReadyCallback {

    private static final LatLng CENTER = new LatLng(-20, 130);
    private static final int MAX_WIDTH_PX = 100;
    private static final int MAX_HUE_DEGREES = 360;
    private static final int MAX_ALPHA = 255;

    private static final int PATTERN_DASH_LENGTH_PX = 50;
    private static final int PATTERN_GAP_LENGTH_PX = 10;
    private static final Dot DOT = new Dot();
    private static final Dash DASH = new Dash(PATTERN_DASH_LENGTH_PX);
    private static final Gap GAP = new Gap(PATTERN_GAP_LENGTH_PX);
    private static final List<PatternItem> PATTERN_DOTTED = Arrays.asList(DOT, GAP);
    private static final List<PatternItem> PATTERN_DASHED = Arrays.asList(DASH, GAP);
    private static final List<PatternItem> PATTERN_MIXED = Arrays.asList(DOT, GAP, DOT, DASH, GAP);

    private Polygon mutablePolygon;
    private SeekBar fillHueBar;
    private SeekBar fillAlphaBar;
    private SeekBar strokeWidthBar;
    private SeekBar strokeHueBar;
    private SeekBar strokeAlphaBar;
    private Spinner strokeJointTypeSpinner;
    private Spinner strokePatternSpinner;
    private CheckBox clickabilityCheckbox;

    // These are the options for polygon stroke joints and patterns. We use their
    // string resource IDs as identifiers.

    private static final int[] JOINT_TYPE_NAME_RESOURCE_IDS = {
            R.string.joint_type_default, // Default
            R.string.joint_type_bevel,
            R.string.joint_type_round,
    };

    private static final int[] PATTERN_TYPE_NAME_RESOURCE_IDS = {
            R.string.pattern_solid, // Default
            R.string.pattern_dashed,
            R.string.pattern_dotted,
            R.string.pattern_mixed,
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.polygon_demo);

        fillHueBar = findViewById(R.id.fillHueSeekBar);
        fillHueBar.setMax(MAX_HUE_DEGREES);
        fillHueBar.setProgress(MAX_HUE_DEGREES / 2);

        fillAlphaBar = findViewById(R.id.fillAlphaSeekBar);
        fillAlphaBar.setMax(MAX_ALPHA);
        fillAlphaBar.setProgress(MAX_ALPHA / 2);

        strokeWidthBar = findViewById(R.id.strokeWidthSeekBar);
        strokeWidthBar.setMax(MAX_WIDTH_PX);
        strokeWidthBar.setProgress(MAX_WIDTH_PX / 3);

        strokeHueBar = findViewById(R.id.strokeHueSeekBar);
        strokeHueBar.setMax(MAX_HUE_DEGREES);
        strokeHueBar.setProgress(0);

        strokeAlphaBar = findViewById(R.id.strokeAlphaSeekBar);
        strokeAlphaBar.setMax(MAX_ALPHA);
        strokeAlphaBar.setProgress(MAX_ALPHA);

        strokeJointTypeSpinner = findViewById(R.id.strokeJointTypeSpinner);
        strokeJointTypeSpinner.setAdapter(new ArrayAdapter<>(
                this, android.R.layout.simple_spinner_item,
                getResourceStrings(JOINT_TYPE_NAME_RESOURCE_IDS)));

        strokePatternSpinner = findViewById(R.id.strokePatternSpinner);
        strokePatternSpinner.setAdapter(new ArrayAdapter<>(
                this, android.R.layout.simple_spinner_item,
                getResourceStrings(PATTERN_TYPE_NAME_RESOURCE_IDS)));

        clickabilityCheckbox = findViewById(R.id.toggleClickability);

        SupportMapFragment mapFragment =
                (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap map) {
        // Override the default content description on the view, for accessibility mode.
        map.setContentDescription(getString(R.string.polygon_demo_description));

        int fillColorArgb = Color.HSVToColor(
                fillAlphaBar.getProgress(), new float[]{fillHueBar.getProgress(), 1, 1});
        int strokeColorArgb = Color.HSVToColor(
                strokeAlphaBar.getProgress(), new float[]{strokeHueBar.getProgress(), 1, 1});

        // Create a rectangle with two rectangular holes.
        mutablePolygon = map.addPolygon(new PolygonOptions()
                .addAll(createRectangle(CENTER, 5, 5))
                .addHole(createRectangle(new LatLng(-22, 128), 1, 1))
                .addHole(createRectangle(new LatLng(-18, 133), 0.5, 1.5))
                .fillColor(fillColorArgb)
                .strokeColor(strokeColorArgb)
                .strokeWidth(strokeWidthBar.getProgress())
                .clickable(clickabilityCheckbox.isChecked()));

        fillHueBar.setOnSeekBarChangeListener(this);
        fillAlphaBar.setOnSeekBarChangeListener(this);

        strokeWidthBar.setOnSeekBarChangeListener(this);
        strokeHueBar.setOnSeekBarChangeListener(this);
        strokeAlphaBar.setOnSeekBarChangeListener(this);

        strokeJointTypeSpinner.setOnItemSelectedListener(this);
        strokePatternSpinner.setOnItemSelectedListener(this);

        mutablePolygon.setStrokeJointType(getSelectedJointType(strokeJointTypeSpinner.getSelectedItemPosition()));
        mutablePolygon.setStrokePattern(getSelectedPattern(strokePatternSpinner.getSelectedItemPosition()));

        // Move the map so that it is centered on the mutable polygon.
        map.moveCamera(CameraUpdateFactory.newLatLngZoom(CENTER, 4));

        // Add a listener for polygon clicks that changes the clicked polygon's stroke color.
        map.setOnPolygonClickListener(new GoogleMap.OnPolygonClickListener() {
            @Override
            public void onPolygonClick(Polygon polygon) {
                // Flip the red, green and blue components of the polygon's stroke color.
                polygon.setStrokeColor(polygon.getStrokeColor() ^ 0x00ffffff);
            }
        });
    }

}
PolygonDemoActivity.java

Clone and run the samples

Git is required to run this sample locally. The following command clones the sample application repository.

git clone git@github.com:googlemaps-samples/android-samples.git

Import the sample project into Android Studio:

  1. In Android Studio, select File > New > Import Project.

  2. Go to the location where you saved the repository and select the project directory for Kotlin or Java:

    • Kotlin: PATH-REPO/android-samples/ApiDemos/kotlin
    • Java: PATH-REPO/android-samples/ApiDemos/java
  3. Select Open. Android Studio builds your project, using the Gradle build tool.
  4. Create a blank secrets.properties file in the same directory as your project's local.properties file. For more information, see Add your API key to the project.

  5. Add the following string to secrets.properties, replacing YOUR_API_KEY with the value of your API key:

    MAPS_API_KEY=YOUR_API_KEY
  6. Run the app.