为什么我的应用程序崩溃而没有任何错误？

Question

应用程序崩溃，出现以下错误：

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致命异常：主进程：com.example.ayyan.jellybeanestimator，PID：2960 java.lang.RuntimeException：无法启动活动

ComponentInfo {com.example.ayyan.jellybeanestimator / com.example.ayyan.jellybeanestimator.MainActivity}：java.lang.NumberFormatException：空字符串在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2646）在android.app.ActivityThread .handleLaunchActivity（ActivityThread.java:2707）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1460）在android.os.Handler.dispatchMessage（Handler .java：102），位于android.os.Looper.loop（Looper.java:154），位于android.app.ActivityThread.main（ActivityThread.java:6077），位于java.lang.reflect.Method.invoke（本机方法），位于com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865）位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:755）原因：java.lang.NumberFormatException：空字符串在com.example.ayyan.jell上的java.lang.Double.parseDouble（Double.java:547）上的java.lang.FloatingDecimal.readJavaFormatString（FloatingDecimal.java:1071） ybeanestimator.MainActivity.onCreate（MainActivity.java:25）在android.app.Activity.performCreate（Activity.java:6662）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1118）在android.app.ActivityThread.performLaunchActivity （ActivityThread.java:2599）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2707）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java） ：1460），位于android.os.Handler.dispatchMessage（Handler.java：102），位于android.os.Looper.loop（Looper.java：154），位于android.app.ActivityThread.main（ActivityThread.java：6077），位于Java com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865）上的.lang.reflect.Method.invoke（本机方法），com.android.internal.os.ZygoteInit.main（ZygoteInit.java： 755）

package com.example.ayyan.jellybeanestimator;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.EditText;
import android.widget.Button;   
import android.content.Intent;
import android.view.View;

public class MainActivity extends AppCompatActivity {
EditText jellyBeanLength, jellyBeanDiameter, jarSizeVolume;
double jellybeantall, jellybeanfat, jellybeanspace;
double loadFactor = .698;
TextView answer;

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

    jellyBeanLength = (EditText) findViewById (R.id.length);
    jellyBeanDiameter = (EditText) findViewById (R.id.diameter);
    jarSizeVolume = (EditText) findViewById (R.id.jarsize);
    jellybeantall = Double.parseDouble(jellyBeanLength.getText().toString());
    jellybeanfat = Double.parseDouble(jellyBeanDiameter.getText().toString());
    jellybeanspace = Double.parseDouble(jarSizeVolume.getText().toString());
    answer = (TextView) findViewById (R.id.answer);
    Button calculate = (Button) findViewById (R.id.calculate);
    calculate.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this, MainActivity.class));
        }
    });



    double volumeOfOneJellyBean =  ((3.14159265359/6)*(jellybeanfat*jellybeanfat)*jellybeantall);
    double volumeofBeans = (jellybeanspace*loadFactor);
    float numberOfBeans = (float)Math.round (volumeofBeans/volumeOfOneJellyBean);
    answer.setText("You have this amount of beans in your jar" + numberOfBeans);
}

}

Answer 1

检查是否在EditText插入了任何值，然后仅将其解析为Double

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

        jellyBeanLength = (EditText) findViewById (R.id.length);
        jellyBeanDiameter = (EditText) findViewById (R.id.diameter);
        jarSizeVolume = (EditText) findViewById (R.id.jarsize);

        answer = (TextView) findViewById (R.id.answer);
        Button calculate = (Button) findViewById (R.id.calculate);
        calculate.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

//Take out value when button pressed
        jellybeantall = Double.parseDouble(TextUtils.isEmpty(jellyBeanLength.getText().toString())?"0":jellyBeanLength.getText().toString());
        jellybeanfat = Double.parseDouble(TextUtils.isEmpty(jellyBeanDiameter.getText().toString())?"0":jellyBeanDiameter.getText().toString());
        jellybeanspace = Double.parseDouble(TextUtils.isEmpty(jarSizeVolume.getText().toString())?"0":jarSizeVolume.getText().toString());



        double volumeOfOneJellyBean =  ((3.14159265359/6)*(jellybeanfat*jellybeanfat)*jellybeantall);
        double volumeofBeans = (jellybeanspace*loadFactor);
        float numberOfBeans = (float)Math.round (volumeofBeans/volumeOfOneJellyBean);
        answer.setText("You have this amount of beans in your jar" + numberOfBeans);
            } 
        }); 
    } 

Answer 2

您应该计算按钮的onClick。在您的代码中，您没有输入任何值并试图进行计算。

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

    jellyBeanLength = (EditText) findViewById (R.id.length);
    jellyBeanDiameter = (EditText) findViewById (R.id.diameter);
    jarSizeVolume = (EditText) findViewById (R.id.jarsize);
    jellybeantall = Double.parseDouble(jellyBeanLength.getText().toString());
    jellybeanfat = Double.parseDouble(jellyBeanDiameter.getText().toString());
    jellybeanspace = Double.parseDouble(jarSizeVolume.getText().toString());
    answer = (TextView) findViewById (R.id.answer);
    Button calculate = (Button) findViewById (R.id.calculate);
    calculate.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
    double volumeOfOneJellyBean =  ((3.14159265359/6)*(jellybeanfat*jellybeanfat)*jellybeantall);
    double volumeofBeans = (jellybeanspace*loadFactor);
    float numberOfBeans = (float)Math.round (volumeofBeans/volumeOfOneJellyBean);
    answer.setText("You have this amount of beans in your jar" + numberOfBeans);
        }
    });
}

Answer 3

EditText字段中没有任何值，您正尝试解析该值。因此，错误java.lang.NumberFormatException：空字符串。

Answer 4

您可以尝试更改：

answer.setText("You have this amount of beans in your jar" + numberOfBeans);

至

answer.setText("You have this amount of beans in your jar" + String.valueOf(numberOfBeans));

这应该将双精度型转换为字符串。

Answer 5

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    try
    {
       jellyBeanLength = (EditText) findViewById (R.id.length);
        jellyBeanDiameter = (EditText) findViewById (R.id.diameter);
        jarSizeVolume = (EditText) findViewById (R.id.jarsize);
        jellybeantall = Double.parseDouble(jellyBeanLength.getText().toString());
        jellybeanfat = Double.parseDouble(jellyBeanDiameter.getText().toString());
        jellybeanspace = Double.parseDouble(jarSizeVolume.getText().toString());
        answer = (TextView) findViewById (R.id.answer);
        Button calculate = (Button) findViewById (R.id.calculate);
        calculate.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
        double volumeOfOneJellyBean =  ((3.14159265359/6)*(jellybeanfat*jellybeanfat)*jellybeantall);
        double volumeofBeans = (jellybeanspace*loadFactor);
        float numberOfBeans = (float)Math.round (volumeofBeans/volumeOfOneJellyBean);
        answer.setText("You have this amount of beans in your jar" + numberOfBeans);
        }
        });
    } 
    catch (Exception e) 
    {
       e.printStackTrace();
    }
}