应用程序崩溃，我收到了这些错误：
致命的例外：主要 过程：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：empty String 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） 在android.os.Looper.loop（Looper.java:154） 在android.app.ActivityThread.main（ActivityThread.java:6077） at java.lang.reflect.Method.invoke（Native Method） 在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:755） 引起：java.lang.NumberFormatException：空字符串 在 java.lang.FloatingDecimal.readJavaFormatString（FloatingDecimal.java:1071） 在java.lang.Double.parseDouble（Double.java:547） 在 com.example.ayyan.jellybeanestimator.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） 在android.os.Handler.dispatchMessage（Handler.java:102） 在android.os.Looper.loop（Looper.java:154） 在android.app.ActivityThread.main（ActivityThread.java:6077） at java.lang.reflect.Method.invoke（Native Method） 在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865） 在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);
}
}
答案 0 :(得分：1)
你应该计算onClick of button。在你的代码中你没有输入任何值并试图计算它。
@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);
}
});
}
答案 1 :(得分：1)
检查EditText中是否插入了任何值，然后仅在Double中解析
@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);
}
});
}
答案 2 :(得分：0)
EditText字段中没有值，并且您正在尝试解析该值。因此错误java.lang.NumberFormatException：empty String。
答案 3 :(得分：-1)
@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();
}
}
答案 4 :(得分：-1)
您可以尝试更改：
answer.setText("You have this amount of beans in your jar" + numberOfBeans);
到
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。