pie-chart - 空对象引用上的 MPAndroidChart PieChart setData

Question

我的饼图 setData 中有错误。我已经尝试过可能的样本，甚至是基本的，但这种情况不断出现。

尝试在空对象引用上调用虚拟方法 'void com.github.mikephil.charting.charts.PieChart.setData(com.github.mikephil.charting.data.ChartData)'

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.de.curtains, PID: 18911
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.de.curtains/com.de.curtains.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.github.mikephil.charting.charts.PieChart.setData(com.github.mikephil.charting.data.ChartData)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3308)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3457)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2044)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:224)
        at android.app.ActivityThread.main(ActivityThread.java:7562)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.github.mikephil.charting.charts.PieChart.setData(com.github.mikephil.charting.data.ChartData)' on a null object reference
        at com.de.curtains.MainActivity.onCreate(MainActivity.java:79)
        at android.app.Activity.performCreate(Activity.java:7893)

<com.github.mikephil.charting.charts.PieChart
     android:id="@+id/pieChart"
     android:layout_width="match_parent"
     android:layout_height="match_parent"/>```



`
private PieChart pieChart;
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        pieChart = findViewById(R.id.pieChart);

        List<PieEntry> entries = new ArrayList<>();
        entries.add(new PieEntry(18.5f, "Green"));
        entries.add(new PieEntry(26.7f, "Yellow"));
        entries.add(new PieEntry(24.0f, "Red"));
        entries.add(new PieEntry(30.8f, "Blue"));

        PieDataSet dataSet = new PieDataSet(entries, "Election Results");
        PieData data = new PieData(dataSet);
        pieChart.setData(data);
}

标签： pie-chartmpandroidchart