Question

我想使用sqlite中的数据显示饼图。我将数据输出到列表中以获得饼图的条目。但是代码似乎有问题，我不知道它有什么问题。下面是代码。

public class chart extends Activity {

SQLiteDatabase SQ;

@Override
protected void onCreate (Bundle savedInstanceState){
…
    //add data
    addData();

    //customize legends
    Legend l=mChart.getLegend();
    l.setPosition(Legend.LegendPosition.RIGHT_OF_CHART);
    l.setXEntrySpace(7);
    l.setYEntrySpace(5);

}

public ArrayList<String> queryXData(){
    ArrayList<String> xNewData = new ArrayList<String>();
    String query="SELECT "+ TableInfo.APPLIANCE +" FROM "+TableInfo.TABLE_NAME;
    Cursor cursor = SQ.rawQuery(query,null);
    for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext()){
        xNewData.add(cursor.getString(0));
    }
    cursor.close();
    return xNewData;
}

public ArrayList<Integer> queryYData(){
    ArrayList<Integer> yNewData= new ArrayList<Integer>();
    String query="SELECT "+ TableInfo.POWER_USED +" FROM "+TableInfo.TABLE_NAME;
    Cursor cursor=SQ.rawQuery(query,null);
    for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext()){
        yNewData.add(cursor.getInt(5));
    }
    cursor.close();
    return yNewData;
}

private void addData() {
    ArrayList<Entry> yVals = new ArrayList<Entry>();

    for (int i = 0; i < queryYData().size(); i++)
        yVals.add(new Entry(queryYData().get(i), i));

    ArrayList<String> xVals = new ArrayList<String>();

    for (int i = 0; i < queryXData().size(); i++)
        xVals.add(queryXData().get(i));

    //create pie data set
    PieDataSet dataSet=new PieDataSet(yVals,"Appliances");
    dataSet.setSliceSpace(3); // space between each arc slice
    dataSet.setSelectionShift(5);

    //add many colors
    ArrayList<Integer> colors=new ArrayList<Integer>();

    for(int c: ColorTemplate.VORDIPLOM_COLORS)
        colors.add(c);
    for(int c: ColorTemplate.JOYFUL_COLORS)
        colors.add(c);
    for(int c: ColorTemplate.COLORFUL_COLORS)
        colors.add(c);
    for(int c: ColorTemplate.LIBERTY_COLORS)
        colors.add(c);
    for(int c: ColorTemplate.PASTEL_COLORS)
        colors.add(c);
    colors.add(ColorTemplate.getHoloBlue());
    dataSet.setColors(colors);

    //instantiate pie data object now
    PieData data=new PieData(xVals, dataSet);
    data.setValueFormatter(new PercentFormatter());
    data.setValueTextSize(11f);
    data.setValueTextColor(Color.GRAY);

    mChart.setData(data);

    //undo all highlights
    mChart.highlightValues(null);

    //update pie chart
    mChart.invalidate();

    //demo start
}

}

Aboce是我尝试的代码，但有错误，主要是

chart.queryYData（chart.java:100）Cursor cursor=SQ.rawQuery(query,null); chart.addData（chart.java:111）for (int i = 0; i < queryYData().size(); i++) chart.onCreate（chart.java:76）addData();

这些错误导致应用程序“不幸，应用程序停止了”。有人可以帮我弄这个吗？谢谢。

Answer 1

例如，您需要添加一行来标识mChart。其他代码看起来很好。

 mChart=(PieChart)findViewByID(R.id.pieChart);

MPAndroid不显示饼图

1 个答案: