如何在其他片段中的值发生更改时更新片段

Question

我试图用我正在计算的另一个片段中的值在片段中绘制一个图。另一个片段正在更改类中的静态变量(AnalysedTweet)，在片段中使用这些变量绘制图形。

有办法更新图表吗？(用上面的图表更新片段)

这是图片段的代码：

public class Statistics extends Fragment {

    GraphicalView mChartView= null;
    private DefaultRenderer mRenderer = new DefaultRenderer();
    private CategorySeries mSeries = new CategorySeries("Sentiment");
    private int[] COLORS = new int[] {Color.parseColor("#009900"),Color.RED, Color.GRAY};

    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        View rootView = inflater.inflate(R.layout.activity_statistics,  container, false);
        int[] count = new int[3];
        count[0] = AnalysedTweet.getCount_pos();
        count[1] = AnalysedTweet.getCount_neg();
        count[2] = AnalysedTweet.getCount_obj();

        String[] categoryNames = {"Positive","Negative","Objective" };
        for(int i=0;i<3;i++){

        mSeries.add(categoryNames[i], count[i]);
        SimpleSeriesRenderer renderer = new SimpleSeriesRenderer();
        renderer.setColor(COLORS[i]);
        renderer.setDisplayChartValues(true);
        mRenderer.addSeriesRenderer(renderer);

        }


        mChartView = ChartFactory.getPieChartView(this.getActivity(), mSeries, mRenderer);

        Log.i("CHART", Integer.toString(mSeries.getItemCount()));
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.WRAP_CONTENT);
        mChartView.setLayoutParams(params);
        RelativeLayout layout = (RelativeLayout) rootView.findViewById(R.id.chartsRelativeLayout);
        layout.addView(mChartView);

        return rootView;
    }


    public boolean onCreateOptionsMenu(Menu menu) {
        return true;
    }
}

Answer 1

首先，您不应该在交流中使用静态变量(也称为全局变量)，这是非常糟糕的做法。这就是谷歌在这件事上的建议：

通常，您希望一个片段与另一个片段进行通信，例如根据用户事件更改内容。所有片段到片段的通信都是通过相关的活动完成的。两个片段不应该直接交流。为了允许片段与其活动进行通信，您可以在片段类中定义一个接口并在活动中实现它。片段在其onAttach()生命周期方法中捕获接口实现，然后调用接口方法以便与活动通信。 下面是片段到活动通信的示例：

公共类HeadlinesFragment扩展了ListFragment { OnHeadlineSelectedListener mCallback；

    // Container Activity must implement this interface
    public interface OnHeadlineSelectedListener {
        public void onArticleSelected(int position);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (OnHeadlineSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnHeadlineSelectedListener");
        }
    }

    ...
}

参见更多的heree http://developer.android.com/training/basics/fragments/communicating.html