在得到你们的帮助之后，我建立了一个很棒的应用程序（BMI计算器）。添加搜索栏并清除代码中的所有错误后，应用程序在我测试时无法启动，显示消息＆＃34;应用程序无法正常关闭＆＃34;。
搜索栏是一种可选方法，用于更改textedit字段中的值。
这是MainActiviy.java
package com.example.calculadorimc;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
public class MainActivity extends Activity {
private RadioGroup rgsexo;
EditText editPeso;
EditText editAltura;
TextView imcView;
SeekBar alterarAltura;
SeekBar alterarPeso;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
alterarAltura.setOnSeekBarChangeListener(alteraralturaListener);
editPeso = (EditText)findViewById(R.id.editPeso);
editAltura = (EditText)findViewById(R.id.editAltura);
imcView = (TextView)findViewById(R.id.imcView);
alterarAltura = (SeekBar)findViewById(R.id.alterarAltura);
alterarPeso = (SeekBar)findViewById(R.id.alterarPeso);
}
private OnSeekBarChangeListener alteraralturaListener = new OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
// Calcula o novo valor do TIP
double setAltura = (alterarAltura.getProgress()) * .01d;
// mostra na caixa o valor novo
editAltura.setText(String.format("%.02f", setAltura).replace(',', '.'));
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
};
public void calculateClickHandler(View view) {
// make sure we handle the click of the calculator button
if (view.getId() == R.id.botaoCalcular) {
// get the users values from the widget references
float peso = Float.parseFloat(editPeso.getText().toString());
float altura = Float.parseFloat(editAltura.getText().toString());
// calculate the bmi value
float imcValue = calcularIMC(peso, altura);
// interpret the meaning of the bmi value
String imcInterpretation = interpretIMC(imcValue);
// now set the value in the result text
imcView.setText(imcValue + "-" + imcInterpretation);
}
}
// the formula to calculate the BMI index
// check for http://en.wikipedia.org/wiki/Body_mass_index
private float calcularIMC (float peso, float altura) {
return (float) (peso / (altura * altura));
}
// interpret what BMI means
private String interpretIMC(float imcValue) {
rgsexo = (RadioGroup)findViewById(R.id.rgSexo);
int selectedId = rgsexo.getCheckedRadioButtonId(); // get the id
switch (selectedId) // switch on the button selected
{
case R.id.radioMasc:
if (imcValue < 20) {
return "Abaixo do Peso";
} else if (imcValue < 24.9) {
return "Peso Normal";
} else if (imcValue < 29.9) {
return "Acima do Peso";
} else if (imcValue < 39.9) {
return "Obesidade Moderada";
} else {
return "Obesidade Mórbida";
}
case R.id.radioFem:
if (imcValue < 19) {
return "Abaixo do Peso";
} else if (imcValue < 23.9) {
return "Peso Normal";
} else if (imcValue < 28.9) {
return "Acima do Peso";
} else if (imcValue < 38.9) {
return "Obesidade Moderada";
} else {
return "Obesidade Mórbida";
}
}
return null;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
和Activitymain.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
tools:context=".MainActivity" >
<RadioGroup
android:id="@+id/rgSexo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<RadioButton
android:id="@+id/radioMasc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="@string/radioMasc" />
<RadioButton
android:id="@+id/radioFem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/radioFem" />
</RadioGroup>
<TextView
android:id="@+id/alturaView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/alturaView" />
<EditText
android:id="@+id/editAltura"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="5"
android:inputType="numberDecimal"
android:text="@string/editAltura" >
<requestFocus />
</EditText>
<SeekBar
android:id="@+id/alterarAltura"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="3" />
<TextView
android:id="@+id/pesoView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/pesoView" />
<EditText
android:id="@+id/editPeso"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="5"
android:inputType="number"
android:text="@string/editPeso" />
<SeekBar
android:id="@+id/alterarPeso"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="600" />
<View
android:layout_width="fill_parent"
android:layout_height="2dip"
android:layout_marginBottom="5dip"
android:layout_marginTop="5dip"
android:background="#111111" />
<Button
android:id="@+id/botaoCalcular"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="calculateClickHandler"
android:text="@string/botaoCalcular" />
<TextView
android:id="@+id/imcView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/imcView"
android:textAppearance="?android:attr/textAppearanceLarge" />
感谢您的支持。
P.S。我总计N00b
LogCat文件
03-04 21:18:38.492: D/AndroidRuntime(279): Shutting down
VM
03-04 21:18:38.492: W/dalvikvm(279): threadid=1: thread
exiting with uncaught exception (group=0x4001d800)
03-04 21:18:38.542: E/AndroidRuntime(279): FATAL
EXCEPTION: main
03-04 21:18:38.542: E/AndroidRuntime(279):
java.lang.RuntimeException: Unable to start activity
ComponentInfo
{com.example.calculadorimc/com.example.calculadorimc.Main
Activity}: java.lang.NullPointerException
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2663)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread.handleLaunchActivity
(ActivityThread.java:2679)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread.access$2300
(ActivityThread.java:125)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread$H.handleMessage
(ActivityThread.java:2033)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.os.Handler.dispatchMessage(Handler.java:99)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.os.Looper.loop(Looper.java:123)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread.main(ActivityThread.java:4627)
03-04 21:18:38.542: E/AndroidRuntime(279): at
java.lang.reflect.Method.invokeNative(Native Method)
03-04 21:18:38.542: E/AndroidRuntime(279): at
java.lang.reflect.Method.invoke(Method.java:521)
03-04 21:18:38.542: E/AndroidRuntime(279): at
com.android.internal.os.ZygoteInit
$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-04 21:18:38.542: E/AndroidRuntime(279): at
com.android.internal.os.ZygoteInit.main
(ZygoteInit.java:626)
03-04 21:18:38.542: E/AndroidRuntime(279): at
dalvik.system.NativeStart.main(Native Method)
03-04 21:18:38.542: E/AndroidRuntime(279): Caused by:
java.lang.NullPointerException
03-04 21:18:38.542: E/AndroidRuntime(279): at
com.example.calculadorimc.MainActivity.onCreate
(MainActivity.java:27)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.Instrumentation.callActivityOnCreate
(Instrumentation.java:1047)
03-04 21:18:38.542: E/AndroidRuntime(279): at
android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2627)
03-04 21:18:38.542: E/AndroidRuntime(279): ... 11
more
03-04 21:18:44.231: I/Process(279): Sending signal. PID:
279 SIG: 9
03-04 21:18:48.231: D/AndroidRuntime(286): Shutting down
VM
03-04 21:18:48.231: W/dalvikvm(286): threadid=1: thread
exiting with uncaught exception (group=0x4001d800)
03-04 21:18:48.272: E/AndroidRuntime(286): FATAL
EXCEPTION: main
03-04 21:18:48.272: E/AndroidRuntime(286):
java.lang.RuntimeException: Unable to start activity
ComponentInfo
{com.example.calculadorimc/com.example.calculadorimc.Main
Activity}: java.lang.NullPointerException
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2663)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread.handleLaunchActivity
(ActivityThread.java:2679)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread.access$2300
(ActivityThread.java:125)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread$H.handleMessage
(ActivityThread.java:2033)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.os.Handler.dispatchMessage(Handler.java:99)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.os.Looper.loop(Looper.java:123)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread.main(ActivityThread.java:4627)
03-04 21:18:48.272: E/AndroidRuntime(286): at
java.lang.reflect.Method.invokeNative(Native Method)
03-04 21:18:48.272: E/AndroidRuntime(286): at
java.lang.reflect.Method.invoke(Method.java:521)
03-04 21:18:48.272: E/AndroidRuntime(286): at
com.android.internal.os.ZygoteInit
$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-04 21:18:48.272: E/AndroidRuntime(286): at
com.android.internal.os.ZygoteInit.main
(ZygoteInit.java:626)
03-04 21:18:48.272: E/AndroidRuntime(286): at
dalvik.system.NativeStart.main(Native Method)
03-04 21:18:48.272: E/AndroidRuntime(286): Caused by:
java.lang.NullPointerException
03-04 21:18:48.272: E/AndroidRuntime(286): at
com.example.calculadorimc.MainActivity.onCreate
(MainActivity.java:27)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.Instrumentation.callActivityOnCreate
(Instrumentation.java:1047)
03-04 21:18:48.272: E/AndroidRuntime(286): at
android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2627)
03-04 21:18:48.272: E/AndroidRuntime(286): ... 11
more
03-04 21:18:52.073: I/Process(286): Sending signal. PID:
286 SIG: 9
答案 0 :(得分：2)
在调用方法之前用alterarAltura初始化findViewById()。
答案 1 :(得分：2)
您需要在将字段分配给变量后调用.setOnSeek...，否则alterarAltura将为null并且null上的操作会导致NullPointerException
示例：
editPeso = (EditText)findViewById(R.id.editPeso);
editAltura = (EditText)findViewById(R.id.editAltura);
imcView = (TextView)findViewById(R.id.imcView);
alterarAltura = (SeekBar)findViewById(R.id.alterarAltura);
alterarPeso = (SeekBar)findViewById(R.id.alterarPeso);
alterarAltura.setOnSeekBarChangeListener(alteraralturaListener);