使用日历作为X轴从sqlite创建图表-Java 学习之路

-1

我想创建一个图表日历与整数 . 在表中键入日期格式或将字符串值解析为日期 .

import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.jjoe64.graphview.GraphView;
import com.jjoe64.graphview.helper.DateAsXAxisLabelFormatter;
import com.jjoe64.graphview.series.DataPoint;
import com.jjoe64.graphview.series.LineGraphSeries;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class VIewGraph extends AppCompatActivity {

    LineGraphSeries<DataPoint> series;
    DatabaseHelper mDatabaseHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_graph);
        mDatabaseHelper = new DatabaseHelper(this);

        String y;
        Float z;
        Date d1;
        Cursor data = mDatabaseHelper.readEntry();
        int rows = data.getCount();
        data.moveToFirst();

        GraphView graph = (GraphView) findViewById(R.id.graph11);
        series = new LineGraphSeries<DataPoint>();

        for(int i = 0;  i <rows; i++){
            data.moveToNext();
            String x = data.getString(2);
            y = data.getString(3);
            z = Float.parseFloat(y);   
            Date date1;
            try { 
                date1 = new SimpleDateFormat("dd/MM/yyyy").parse(x);
                 } catch (Exception e) {
                   e.printStackTrace();
                  }

            series.appendData(new DataPoint(date1, z), true, 25);
        }
        graph.addSeries(series);

        graph.getGridLabelRenderer().setNumHorizontalLabels(3);
        graph.getGridLabelRenderer().setHumanRounding(false);

    }
}

这是一些关于getTime（）的代码

import android.app.DatePickerDialog;
import android.app.TimePickerDialog;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.icu.util.Calendar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;
import java.sql.Time;

public class Logging extends AppCompatActivity {

private static final String TAG = "Logging";

DatabaseHelper mDatabaseHelper;
EditText editWeight, editFat, editHydration, editMuscle, editBone, editTime, editASD;
private Button button2;
private TextView mDisplayDate, mDisplayTime;
private DatePickerDialog.OnDateSetListener mDateSetListener;
private TimePickerDialog.OnTimeSetListener mTimeSetListener;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_logging);
    button2 = (Button) findViewById(R.id.button2);
    mDisplayDate = (TextView) findViewById(R.id.tvDate);
    mDatabaseHelper = new DatabaseHelper(this);
    mDisplayTime = (TextView) findViewById(R.id.tvTime);

    editWeight = (EditText) findViewById(R.id.editWeight);
    editFat = (EditText) findViewById(R.id.editFat);
    editHydration = (EditText) findViewById(R.id.editHydration);
    editMuscle = (EditText) findViewById(R.id.editMuscle);
    editBone = (EditText) findViewById(R.id.editBone);

    mDisplayDate.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Calendar cal = Calendar.getInstance();
            int year = cal.get(Calendar.YEAR);
            int month = cal.get(Calendar.MONTH);
            int day = cal.get(Calendar.DAY_OF_MONTH);

            DatePickerDialog dialog = new DatePickerDialog(
                    Logging.this,
                    android.R.style.Theme_Holo_Light_Dialog_MinWidth,
                    mDateSetListener,
                    year,month,day);
            dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
            dialog.show();

        }
    });

    mDateSetListener = new DatePickerDialog.OnDateSetListener() {
        @Override
        public void onDateSet(DatePicker datePicker, int year, int month, int day) {
            month = month + 1;
            Log.d(TAG, "onDateSet: mm/dd/yyyy: " + day + "/" + month + "/" + year);

            String date = day + "/" + month + "/" + year;
            mDisplayDate.setText(date);
        }
    };

    mDisplayTime.setOnClickListener(new View.OnClickListener() {
                                        @Override
                                        public void onClick(View view) {
                                            Calendar mTime = Calendar.getInstance();
                                            int mHour = mTime.get(Calendar.HOUR_OF_DAY);
                                            int mMinute = mTime.get(Calendar.MINUTE);

                                            TimePickerDialog timePickerDialog = new TimePickerDialog(Logging.this,
                                                    new TimePickerDialog.OnTimeSetListener() {

                                                        @Override
                                                        public void onTimeSet(TimePicker view, int hourOfDay,
                                                                              int minute) {

                                                            mDisplayTime.setText(hourOfDay + ":" + minute);
                                                        }
                                                    }, mHour, mMinute, true);
                                            timePickerDialog.show();
                                        }
                                    });

    LogData();
}

public void LogData(){
    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            boolean isInserted = mDatabaseHelper.addData(
                    mDisplayDate.getText().toString(),
                    mDisplayTime.getText().toString(),
                    editWeight.getText().toString(),
                    editFat.getText().toString(),
                    editHydration.getText().toString(),
                    editMuscle.getText().toString(),
                    editBone.getText().toString()
            );
            if (isInserted == true)
                Toast.makeText(Logging.this, "Data Inserted", Toast.LENGTH_LONG).show();
            else
                Toast.makeText(Logging.this, "Data not Inserted", Toast.LENGTH_LONG).show();
        }
    });
}

}

现在错误发生在Logcat上：

08-19 21：58：50.313 25858-25858 / example.christopher.bd E / AndroidRuntime：FATAL EXCEPTION：main进程：example.christopher.bd，PID：25858 java.lang.RuntimeException：无法启动活动ComponentInfo {example . christopher.bd/example.christopher.bd.VIewGraph}：java.lang.NullPointerException：尝试在android.app.ActivityThread.performLaunchActivity上的空对象引用上调用虚方法'long java.util.Date.getTime（）'（ ActivityThread.java:2913）在Android.app.servert事件中的android.app.ActivityThread.handleLaunchActivity（ActivityThread.java：3048）处于android.app.servertransaction.TransactionExecutor.executeCallbacks（TransactionExecutor）的android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:78） .java：108）在Android.app.Handler.dispatchMessage（处理程序 . ）的android.app.AvertThread $ H.handleMessage（ActivityThread.java:1808）的android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68） . java：106）在androi的android.os.Looper.loop（Looper.java:193） d.app.ActivityThread.main（ActivityThread.java:6669）at java.lang.reflect.Method.invoke（Native Method）at com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:493）at at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:858）引起：java.lang.NullPointerException：尝试在空对象引用上调用虚方法'long java.util.Date.getTime（）' com.jjoe64.graphview.series.DataPoint . （DataPoint.java:45）在example.christopher.bd.VIewGraph.onCreate（VIewGraph.java:48）的android.app.Activity.performCreate（Activity.java:7136）at at Android.app.A活动中的android.app.Activity.performCreate（Activity.java:7127）安卓android.app.Anstrumentation.callActivityOnCreate（Instrumentation.java:1271），android.app.ActivityThread，Android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2893） .handleLaunchActivity（ActivityThread.java:3048）在android.app.servertransaction.TransactionExecuto的android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:78）在android.app.Handler的android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1808）的android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68）上的r.executeCallbacks（TransactionExecutor.java:108） .dispatchMessage（Handler.java:106）位于android.app.Looper.loop（Looper.java:193）的android.app.ActivityThread.main（ActivityThread.java:6669），位于java.lang.reflect.Method.invoke（本地方法）com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:493）at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:858）

谁能帮我？谢谢

2 回答

0
改变这一行：

Date date1 = new SimpleDateFormat("dd/MM/yyyy").parse(x);

至：
```
Date date1 = null;
   try { 
        date1 = new SimpleDateFormat("dd/MM/yyyy").parse(x);
    } catch (Exception e) {
        e.printStackTrace();
    }
```
这应该可以解决您的问题 .

Parse 要求它在try catch下，因为 Parse 不知道将向它提供什么类型的字符串 .
回复于 2024-05-03T10:30:48+08:00
0
请参阅import语句中的ViewGraph Activity文件：
```
import java.sql.Time; // Delete this line
```
写这一行：
```
import java.util.Time;
```
这将现在奏效 .
回复于 2024-05-03T10:30:48+08:00

使用日历作为X轴从sqlite创建图表

2 回答

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