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嗨，我是 android 新手，我编写了以下代码来绘制折线图。我正在使用数据库将值传递给图表但图表没有绘制。

您能否告诉我如何更改以下代码以绘制条形图。

import org.achartengine.ChartFactory;
import org.achartengine.chart.PointStyle;
import org.achartengine.model.TimeSeries;
import org.achartengine.model.XYMultipleSeriesDataset;
import org.achartengine.renderer.XYMultipleSeriesRenderer;
import org.achartengine.renderer.XYSeriesRenderer;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Color;
public class ChartActivity<BMICalculatorDB> extends Activity{

    public ChartActivity() {
        super();
    }
        public ChartActivity(Context context, String name, CursorFactory factory,
            int version, DatabaseErrorHandler errorHandler) {
        super();
        // TODO Auto-generated constructor stub
    }


        public static final String KEY_BMIID = "bmi_id";
        public static final String KEY_BMIDATA = "bmi_data";
        public static final String KEY_BMIDATE = "bmi_date";

        private static final String DATABASE_NAME = "Jayant";
        private static final String DATABASE_TABLE = "android_metadata";
        private static final int DATABASE_VERSION = 2;

        private DBHelper ourHelper;
        private static Context ourContext;
        private SQLiteDatabase ourDatabase;

        private static class DBHelper extends SQLiteOpenHelper{

            public DBHelper(Context context) {
                super(context, DATABASE_NAME, null, DATABASE_VERSION);
                // TODO Auto-generated constructor stub
            }

            @Override
            public void onCreate(SQLiteDatabase db) {
                // TODO Auto-generated method stub
                db.execSQL( "CREATE TABLE " + DATABASE_TABLE + " (" +
                KEY_BMIID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                        KEY_BMIDATA + " TEXT NOT NULL, " +
                        KEY_BMIDATE + " TEXT NOT NULL );"
                        );
            }

            @Override
            public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                // TODO Auto-generated method stub
                db.execSQL( "DROP TABLE IF EXISTS " + DATABASE_TABLE );
                onCreate(db);
            }

        }

        public void BMICalculatorDB(Context c){
            ourContext = c;
        }

        @SuppressWarnings("unchecked")
        public BMICalculatorDB open(){
            ourHelper = new DBHelper(ourContext);
            ourDatabase = ourHelper.getWritableDatabase();
            return (BMICalculatorDB) this;
        }

        public void close(){
            ourHelper.close();
        }

        public long createEntry( String data, String date ) {
            //, String date 
            // TODO Auto-generated method stub
            ContentValues cv = new ContentValues();
            cv.put(KEY_BMIDATA, data);
            cv.put(KEY_BMIDATE, date);
            return ourDatabase.insert(DATABASE_TABLE, null, cv);
        }

        public String getBMIID() {
            // TODO Auto-generated method stub
            String[] column =
                    new String[]{ KEY_BMIID };
            Cursor c = 
                    ourDatabase.query(DATABASE_TABLE, column, null, null, null, null, null);

            String result = "";
            int iID = c.getColumnIndex(KEY_BMIID);

            for ( c.moveToFirst(); ! c.isAfterLast(); c.moveToNext() ){
                result = result + c.getString(iID);
            }

            return result;
        }

        public String getBMIDataData(){

            String[] column =
                        new String[]{ KEY_BMIDATA };
                Cursor c = 
                        ourDatabase.query( DATABASE_TABLE, column, null, null, null, null, null );

                String result = "";
                int iData = c.getColumnIndex( KEY_BMIDATA );

                for ( c.moveToFirst(); ! c.isAfterLast(); c.moveToNext() ){
                    result = result + c.getString( iData );
                }


            return result;
        }

        public String getBMIDateData(){
            String[] column =
                    new String[]{ KEY_BMIDATE };
            Cursor c = 
                    ourDatabase.query( DATABASE_TABLE, column, null, null, null, null, null );

            String result = "";
            int iDate = c.getColumnIndex( KEY_BMIDATE);

            for ( c.moveToFirst(); ! c.isAfterLast(); c.moveToNext() ){
                result = result + c.getString( iDate );
            }


        return result;
        }

        public void updateEntry( long lId, String mData, String mDate ) {
            // TODO Auto-generated method stub
            ContentValues cvUpdate = new ContentValues();

            cvUpdate.put( KEY_BMIDATA, mData );
            cvUpdate.put( KEY_BMIDATE, mDate );
            ourDatabase.update( DATABASE_TABLE, cvUpdate, KEY_BMIID + " = lId", null );
        }

        public String getData(long l) {
            // TODO Auto-generated method stub
            return null;
        }

        public String getDate(long l) {
            // TODO Auto-generated method stub
            return null;
        }

        public XYMultipleSeriesDataset getDemoDataset(String title) {

            String[] column =
                    new String[]{ KEY_BMIDATA };
            Cursor c = ourHelper.getWritableDatabase().query( DATABASE_TABLE, column, null, null, null, null, null );

            XYMultipleSeriesDataset dataset = new XYMultipleSeriesDataset();

            TimeSeries series = new TimeSeries("Bar1");
            TimeSeries series2 = new TimeSeries(title);

            getBMIDataData();

            while (!c.isAfterLast()) {
                int date = c.getInt((Integer) c.getColumnIndexOrThrow("DAYS"));
                int weight = c.getInt((Integer) c.getColumnIndexOrThrow("TOP 10"));
                series2.add(weight, date);
                c.moveToNext();
            }

            c.close();

            dataset.addSeries(series);
            dataset.addSeries(series2);

            return dataset;
        }


        public Intent getIntent(Context context) {

            //Lager TimeSeries for den første linja
            XYMultipleSeriesDataset dataset = getDemoDataset("Bar1");

            //Kode for render
            XYMultipleSeriesRenderer mRenderer = new XYMultipleSeriesRenderer();

            //Optimalisering linje1
            XYSeriesRenderer renderer = new XYSeriesRenderer();
            renderer.setColor(Color.YELLOW);
            renderer.setPointStyle(PointStyle.CIRCLE);
            renderer.setFillPoints(true);

            // Optimalisering linje2 husk rekke følgen
            XYSeriesRenderer renderer2 = new XYSeriesRenderer();
            renderer2.setColor(Color.BLUE);
            renderer2.setPointStyle(PointStyle.SQUARE);
            renderer2.setFillPoints(true);

            //Legger til render seriene
            mRenderer.addSeriesRenderer(renderer);

            //Optimalisering grafen
            mRenderer.setChartTitle("Test");
            mRenderer.setZoomEnabled(true);
            mRenderer.setZoomButtonsVisible(true);
            mRenderer.setBackgroundColor(Color.BLACK);
            mRenderer.setApplyBackgroundColor(true);
            mRenderer.setXTitle("Dager");
            mRenderer.setShowGrid(true);

            mRenderer.addSeriesRenderer(renderer2);


            Intent intent = ChartFactory.getLineChartIntent(context, dataset, 
                    mRenderer, "Bar Graph Title");

            return intent;

        }

        public void onCreate(SQLiteDatabase db) {
            // TODO Auto-generated method stub

        }

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // TODO Auto-generated method stub

        }
    }
4

1 回答 1

1

只需添加一个空的构造函数并从内部调用 super()

public ChartActivity() {
    super();
}

它应该工作。问题在这里：

Caused by: java.lang.InstantiationException: can't instantiate class flu.solutions.travelsense.ChartActivity; no empty constructor
于 2012-12-12T11:19:11.080 回答