应用程序在从文件中读取数据并在Android中绘制图形时冻结

Question

我使用的是Windows 7,64位和Android Studio。

我正在完成两项任务 -

1. 从doInBackground中的AsyncTaskRunner中的文件读取数据。然后我发布进度并传递数据。

2. 正在进行更新，我正在阅读数据并将其绘制到图表中。

我正在使用GraphView绘制图表。

问题 - 我的应用程序在几秒钟后冻结，“应用程序没有响应”显示。

我是Android编程的新手，所以请指导我。

这是代码 -

package com.example.user.ui_layout;

//import java.util.Random;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.BufferedReader;

import com.jjoe64.graphview.GraphView;
import com.jjoe64.graphview.Viewport;
import com.jjoe64.graphview.series.DataPoint;
import com.jjoe64.graphview.series.LineGraphSeries;
import com.jjoe64.graphview.GridLabelRenderer;

import android.os.AsyncTask;
import android.graphics.Color;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {
    //private static final Random RANDOM = new Random();
    private LineGraphSeries<DataPoint> series;
    private int lastX = 0;

    String line;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        GraphView graphView = (GraphView) findViewById(R.id.graph);
        GridLabelRenderer gridLabelRenderer = graphView.getGridLabelRenderer();

        series = new LineGraphSeries<DataPoint>();
        series.setColor(Color.RED);
        graphView.addSeries(series);

        Viewport viewport = graphView.getViewport();
        viewport.setScrollable(false);
        viewport.setScalable(true);

        viewport.setYAxisBoundsManual(true);
        viewport.setMinY(-50);
        viewport.setMaxY(300);

        viewport.setXAxisBoundsManual(true);
        viewport.setMinX(0);
        viewport.setMaxX(200);


        new AsyncTaskRunner().execute("");
    }


    private class AsyncTaskRunner extends AsyncTask<String, Integer, String>
    {
        @Override
        protected String doInBackground(String... params) {
            try {
                Thread.sleep(3000);                 //1000 milliseconds is one second.
            } catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
            File sdcard = Environment.getExternalStorageDirectory();
            File file = new File(sdcard, "demo.txt");
            try {
                BufferedReader br = new BufferedReader(new FileReader(file));
                while ((line = br.readLine()) != null)
                {
                    int y = Integer.parseInt(line);
                        publishProgress(y);


                }
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return line;
        }

        @Override
        protected void onPostExecute(String result)
        {

        }

        @Override
        protected void onPreExecute()
        {

        }

        @Override
        protected void onProgressUpdate(Integer... s)
        {

            series.appendData(new DataPoint(lastX++, s[0]), true, 1800);


        }

    }
}