使用JSON数据绘制线图，Android [英] Plotting Line Graph with JSON data, Android

问题描述

我是Android开发的初学者，我正在为课堂做app。我的意思是在应用程序中显示JSON数据作为文本和图形。我正在使用Retrofit 2在一个活动中将其显示为文本，但我遇到图形问题，我不知道该怎么做（我还在学习，到目前为止我所做的一切都是在帮助来自教程）。

I'm total beginner in Android development and I'm doing app for class. My assigment is to display JSON data in application as text and graphs. I'm using Retrofit 2 to display it as text in one activity, but I'm having problems with graphs, I don't know how to do it (I'm still learning, everything I've done so far was with help from tutorials).

数据看起来像这样（这是一个例子）：

The data looks like this (this is an example):

{
"id": 1,
"measurements": [{
    "time": "18:25:43",
    "value": 25.4
},
{
    "time": "18:35:43",
    "value": 27.3
},
{
    "time": "18:45:21",
    "value": 26.3
},
{
    "time": "18:55:43",
    "value": 25.2
},
{
    "time": "19:05:43",
    "value": 25.2
},
{
    "time": "19:15:43",
    "value": 25.2
},
{
    "time": "19:25:43",
    "value": 24.9
}]
}

我发现这个，但我不知道下一步该做什么。我应该用数据制作两个数组列表（如果这是答案，怎么做？），或者有更好的解决方案，直接需要时间和价值，并将时间图绘制为X轴和值为Y轴。

I've found this, but I'm not sure what to do next. Should I make two array lists with data(if that's the answer, how to do that?), or there's better solution that directly takes time and value and plots graph with time as X-axis and value as Y-axis.

推荐答案

这是您的解决方案。

首先，您必须添加依赖项

First you have to add in dependencies

dependencies{
  compile 'com.github.PhilJay:MPAndroidChart:v2.2.3'
  ....}

现在在你的xml中添加以下代码

Now in your xml add below code

<com.github.mikephil.charting.charts.LineChart
                android:id="@+id/chart1"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />

现在在你的Java代码中

And now in your Java code

ArrayList<Entry> x;
ArrayList<String> y;
private LineChart mChart;
public String TAG = "YOUR CLASS NAME";

内部onCreate方法

Inside onCreate Method

    x = new ArrayList<Entry>();
    y = new ArrayList<String>();
    mChart = (LineChart) view.findViewById(R.id.chart1);
    mChart.setDrawGridBackground(false);
    mChart.setDescription("");
    mChart.setTouchEnabled(true);
    mChart.setDragEnabled(true);
    mChart.setScaleEnabled(true);
    mChart.setPinchZoom(true);
    mChart.setMarkerView(mv);
    XAxis xl = mChart.getXAxis();
    xl.setAvoidFirstLastClipping(true);
    YAxis leftAxis = mChart.getAxisLeft();
    leftAxis.setInverted(true);
    YAxis rightAxis = mChart.getAxisRight();
    rightAxis.setEnabled(false);
    Legend l = mChart.getLegend();
    l.setForm(Legend.LegendForm.LINE);

点击按钮调用此方法。

private void drawChart() {

    String tag_string_req = "req_chart";

    StringRequest strReq = new StringRequest(Request.Method.POST, "YOUR URL",
            new Response.Listener<String>() {

                @Override
                public void onResponse(String response) {

                    Log.d(TAG, "Response: " + response);

                    try {
                        JSONObject jsonObject = new JSONObject(response);
                        String id = jsonObject.getString("id");
                        JSONArray jsonArray = jsonObject.getJSONArray("measurements");
                        for (int i = 0; i < jsonArray.length(); i++) {

                            int value = jsonObject.getInt("value");
                            String date = jsonObject.getString("time");
                            x.add(new Entry(value, i));
                            y.add(date);

                        }
                        LineDataSet set1 = new LineDataSet(x, "NAV Data Value");
                        set1.setLineWidth(1.5f);
                        set1.setCircleRadius(4f);
                        LineData data = new LineData(y, set1);
                        mChart.setData(data);
                        mChart.invalidate();

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e(TAG, "Error: " + error.getMessage());
        }
    });
    strReq.setRetryPolicy(new RetryPolicy() {

        @Override
        public void retry(VolleyError arg0) throws VolleyError {
        }

        @Override
        public int getCurrentTimeout() {
            return 0;
        }

        @Override
        public int getCurrentRetryCount() {
            return 0;
        }
    });
    strReq.setShouldCache(false);
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

此处的AppController代码

AppController code as here

public class AppController extends Application {
public static final String TAG = AppController.class.getSimpleName();
private RequestQueue mRequestQueue;
private static AppController mInstance;
@Override
public void onCreate() {
    super.onCreate();
    mInstance = this;
}

  public static synchronized AppController getInstance() {
    return mInstance;
}

public RequestQueue getRequestQueue() {
    if (mRequestQueue == null) {
        mRequestQueue = Volley.newRequestQueue(getApplicationContext());
    }
    return mRequestQueue;
}

public <T> void addToRequestQueue(Request<T> req, String tag) {
    req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
    getRequestQueue().add(req);
}
 }

希望这对您有所帮助。如果遇到任何问题，请告诉我。

Hope this will help you. If any issue faced let me know.

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