How to draw a pie chart in android

Download the jar from

http://www.achartengine.org/content/download.html

Add the jar to the projects lib folder. There is a sample also provided by the developers. You can check that and modify the same as you wish.

There is also a demo @

http://www.achartengine.org/content/demo.html

The docs

http://www.achartengine.org/content/javadoc/org/achartengine/chart/PieChart.html

Example:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:id="@+id/chart"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal" >
    </LinearLayout>

</LinearLayout>

The Activity class

public class AChartEnginePieChartActivity extends Activity { 

    private static int[] COLORS = new int[] { Color.GREEN, Color.BLUE,Color.MAGENTA, Color.CYAN };

    private static double[] VALUES = new double[] { 10, 11, 12, 13 };

    private static String[] NAME_LIST = new String[] { "A", "B", "C", "D" };

    private CategorySeries mSeries = new CategorySeries("");

    private DefaultRenderer mRenderer = new DefaultRenderer();

    private GraphicalView mChartView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mRenderer.setApplyBackgroundColor(true);
        mRenderer.setBackgroundColor(Color.argb(100, 50, 50, 50));
        mRenderer.setChartTitleTextSize(20);
        mRenderer.setLabelsTextSize(15);
        mRenderer.setLegendTextSize(15);
        mRenderer.setMargins(new int[] { 20, 30, 15, 0 });
        mRenderer.setZoomButtonsVisible(true);
        mRenderer.setStartAngle(90);

        for (int i = 0; i < VALUES.length; i++) {
            mSeries.add(NAME_LIST[i] + " " + VALUES[i], VALUES[i]);
            SimpleSeriesRenderer renderer = new SimpleSeriesRenderer();
            renderer.setColor(COLORS[(mSeries.getItemCount() - 1) % COLORS.length]);
            mRenderer.addSeriesRenderer(renderer);
        }

        if (mChartView != null) {
            mChartView.repaint();
        }

    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mChartView == null) {
            LinearLayout layout = (LinearLayout) findViewById(R.id.chart);
            mChartView = ChartFactory.getPieChartView(this, mSeries, mRenderer);
            mRenderer.setClickEnabled(true);
            mRenderer.setSelectableBuffer(10);

            mChartView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint();

                    if (seriesSelection == null) {
                        Toast.makeText(AChartEnginePieChartActivity.this,"No chart element was clicked",Toast.LENGTH_SHORT).show();
                    }
                    else {
                        Toast.makeText(AChartEnginePieChartActivity.this,"Chart element data point index "+ (seriesSelection.getPointIndex()+1) + " was clicked" + " point value="+ seriesSelection.getValue(), Toast.LENGTH_SHORT).show();
                    }
                }
            });

            mChartView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint();
                    if (seriesSelection == null) {
                        Toast.makeText(AChartEnginePieChartActivity.this,"No chart element was long pressed", Toast.LENGTH_SHORT);
                        return false; 
                    }
                    else {
                        Toast.makeText(AChartEnginePieChartActivity.this,"Chart element data point index "+ seriesSelection.getPointIndex()+ " was long pressed",Toast.LENGTH_SHORT);
                        return true;       
                    }
                }
            });
            layout.addView(mChartView, new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
        }
        else {
        mChartView.repaint();
        }
    }
}

Alternatively, if you don't want to use thrid-party libraries, you can use this formula to get points on the circle, given radius r:

x = r * Math.cos(2 * Math.PI) //This will give you r
y = r * Math.sin(2 * Math.PI) //This will give you 0

For other points of the circle you need to modify your cosine argument, for example:

x = r * Math.cos(2 * Math.PI / 6) //This will give you r/2
y = r * Math.sin(2 * Math.PI / 6) //This will give you r*sqrt(3/2)

If you want to fill out the entire circle with a fixed step n:

for(int i=0;i<n;i++) {
    x = r * Math.cos(2 * Math.PI * i / n)
    y = r * Math.sin(2 * Math.PI * i / n)
    //Draw PointF(x,y)
}