Question

我的项目需要使用简单的条形图。我尝试使用aChartEngine，我在启动图表意图中遇到错误和应用程序崩溃。最后我可以运行任何aChartEngin示例。任何人都可以帮我吗？

private String[] mMonth = new String[] { "Jan", "Feb", "Mar", "Apr", "May",
        "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.barchart_form);

    // Getting reference to the button btn_chart
    Button btnChart = (Button) findViewById(R.id.add);

    // Defining click event listener for the button btn_chart
    OnClickListener clickListener = new OnClickListener() {

        @Override
        public void onClick(View v) {
            // Draw the Income vs Expense Chart
            openChart();
        }
    };

    // Setting event click listener for the button btn_chart of the
    // MainActivity layout
    btnChart.setOnClickListener(clickListener);

}

private void openChart() {
    int[] x = { 0, 1, 2, 3, 4, 5, 6, 7 };
    int[] income = { 2000, 2500, 2700, 3000, 2800, 3500, 3700, 3800 };
    // int[] expense = {2200, 2700, 2900, 2800, 2600, 3000, 3300, 3400 };

    // Creating an XYSeries for Income
    // CategorySeries incomeSeries = new CategorySeries("Income");
    XYSeries incomeSeries = new XYSeries("Income");
    // Creating an XYSeries for Income
    // XYSeries expenseSeries = new XYSeries("Expense");
    // Adding data to Income and Expense Series
    for (int i = 0; i < x.length; i++) {
        incomeSeries.add(i, income[i]);
        // expenseSeries.add(i,expense[i]);
    }

    // Creating a dataset to hold each series
    XYMultipleSeriesDataset dataset = new XYMultipleSeriesDataset();
    // Adding Income Series to the dataset
    dataset.addSeries(incomeSeries);
    // Adding Expense Series to dataset
    // dataset.addSeries(expenseSeries);

    // Creating XYSeriesRenderer to customize incomeSeries
    XYSeriesRenderer incomeRenderer = new XYSeriesRenderer();
    incomeRenderer.setColor(Color.rgb(130, 130, 230));
    incomeRenderer.setFillPoints(true);
    incomeRenderer.setLineWidth(2);
    incomeRenderer.setDisplayChartValues(true);

    // Creating XYSeriesRenderer to customize expenseSeries
    // XYSeriesRenderer expenseRenderer = new XYSeriesRenderer();
    // expenseRenderer.setColor(Color.rgb(220, 80, 80));
    // expenseRenderer.setFillPoints(true);
    // expenseRenderer.setLineWidth(2);
    // expenseRenderer.setDisplayChartValues(true);

    // Creating a XYMultipleSeriesRenderer to customize the whole chart
    XYMultipleSeriesRenderer multiRenderer = new XYMultipleSeriesRenderer();
    multiRenderer.setXLabels(0);
    multiRenderer.setChartTitle("Income vs Expense Chart");
    multiRenderer.setXTitle("Year 2012");
    multiRenderer.setYTitle("Amount in Dollars");
    multiRenderer.setZoomButtonsVisible(true);
    for (int i = 0; i < x.length; i++) {
        multiRenderer.addXTextLabel(i, mMonth[i]);
    }

    // Adding incomeRenderer and expenseRenderer to multipleRenderer
    // Note: The order of adding dataseries to dataset and renderers to
    // multipleRenderer
    // should be same
    multiRenderer.addSeriesRenderer(incomeRenderer);
    // multiRenderer.addSeriesRenderer(expenseRenderer);

    // Creating an intent to plot bar chart using dataset and
    // multipleRenderer
    Intent intent = ChartFactory.getBarChartIntent(getBaseContext(),
            dataset, multiRenderer, Type.DEFAULT);

    // Start Activity
    startActivity(intent);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

Answer 1

我的猜测是，以下几行导致了您的问题！

 Intent intent = ChartFactory.getBarChartIntent(getBaseContext(),
            dataset, multiRenderer, Type.DEFAULT);

 // Start Activity
 startActivity(intent);

我的解释是，您在使用NullPointerException时可能有getBaseContext()，因为当您启动新意图以打开新Activity从而破坏活动时，活动的上下文可能会被销毁你想要获得背景的地方。

如果您将getBaseContext()替换为getApplicationContext()，则可以解决问题！

您的解决方案将是：

 Intent intent = ChartFactory.getBarChartIntent(getApplicationContext(),
            dataset, multiRenderer, Type.DEFAULT);

 // Start Activity
 startActivity(intent);

希望它有效！让我知道你的进展

启动intent app崩溃时的achart引擎

1 个答案: