我正在制作一个简单的卡路里计算器，它给了我这个错误，我已经查看了代码并在此处搜索了解决方案，但我无法看出为什么没有运行。 我认为这是因为我没有初始化变量，所以我这样做了，但仍然遇到相同的错误，也许是旋转器的问题，我是使用旋转器的新手
这是代码:
public class CaloriesCalculator extends ActionBarActivity {
EditText etAge, etWeight, etHeight;
Button btnCalculate;
TextView tvResult;
Spinner spinnerGender, spinnerActivity;
String itemGender, itemActivity;
int Height=0;
int Weight=0;
int Age=0;;
double bmr=0.0;
double tdee=0.0;
String result;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.caloriescalculator);
spinnerGender=(Spinner)findViewById(R.id.spinnerGender);
spinnerActivity=(Spinner)findViewById(R.id.spinnerActivity);
etAge=(EditText)findViewById(R.id.etAge);
etWeight=(EditText)findViewById(R.id.etWeight);
etHeight=(EditText)findViewById(R.id.etHeight);
tvResult=(TextView)findViewById(R.id.tvResult);
List<String> list = new ArrayList<String>();
list.add("Male");
list.add("Female");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, list );
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerGender.setAdapter(dataAdapter);
List<String> list2 = new ArrayList<String>();
list.add("Sedentary");
list.add("Lightly Active");
list.add("Moderalety Active");
list.add("Very Active");
list.add("Extremely Active");
ArrayAdapter<String> dataAdapter2 = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, list2 );
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerActivity.setAdapter(dataAdapter2);
btnCalculate.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
spinnerGender.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent,
View view, int position, long id) {
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
spinnerActivity.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent,
View view, int position, long id) {
// TODO Auto-generated method stub
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
itemGender=String.valueOf(spinnerGender.getSelectedItem());
itemActivity=String.valueOf(spinnerActivity.getSelectedItem());
if(itemGender=="Male"){
Weight=Integer.parseInt(etWeight.getText().toString());
Height=Integer.parseInt(etHeight.getText().toString());
Age=Integer.parseInt(etAge.getText().toString());
if(itemActivity=="Sedentary"){
bmr=66+((13.7 * Weight)+(5*Height))-(6.8*Age);
tdee=bmr*1.2;
}
else if(itemActivity=="Lightly Active"){
bmr=66+((13.7 * Weight)+(5*Height))-(6.8*Age);
tdee=bmr*1.375;
}
else if(itemActivity=="Moderalety Active"){
bmr=66+((13.7 * Weight)+(5*Height))-(6.8*Age);
tdee=bmr*1.55;
}
else if(itemActivity=="Very Active"){
bmr=66+((13.7 * Weight)+(5*Height))-(6.8*Age);
tdee=bmr*1.725;
}
else if(itemActivity=="Extremely Active"){
bmr=66+((13.7 * Weight)+(5*Height))-(6.8*Age);
tdee=bmr*1.9;
}
}
else if(itemGender=="Female") {
Weight=Integer.parseInt(etWeight.getText().toString());
Height=Integer.parseInt(etHeight.getText().toString());
Age=Integer.parseInt(etAge.getText().toString());
if(itemActivity=="Sedentary"){
bmr=655+((9.6*Weight)+(1.8*Height))-(4.7*Age);
tdee=bmr*1.2;
}
else if(itemActivity=="Lightly Active"){
bmr=655+((9.6*Weight)+(1.8*Height))-(4.7*Age);
tdee=bmr*1.375;
}
else if(itemActivity=="Moderalety Active"){
bmr=655+((9.6*Weight)+(1.8*Height))-(4.7*Age);
tdee=bmr*1.55;
}
else if(itemActivity=="Very Active"){
bmr=655+((9.6*Weight)+(1.8*Height))-(4.7*Age);
tdee=bmr*1.725;
}
else if(itemActivity=="Extremely Active"){
bmr=655+((9.6*Weight)+(1.8*Height))-(4.7*Age);
tdee=bmr*1.9;
}
}
result=Double.toString(tdee);
tvResult.setText(result);
}
});
}
@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;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
日志猫:
11-28 17:20:05.501: E/AndroidRuntime(1455): FATAL EXCEPTION: main
11-28 17:20:05.501: E/AndroidRuntime(1455): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.calculadoracalorias/com.app.calculadoracalorias.CaloriesCalculator}: java.lang.NullPointerException
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.os.Handler.dispatchMessage(Handler.java:99)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.os.Looper.loop(Looper.java:137)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-28 17:20:05.501: E/AndroidRuntime(1455): at java.lang.reflect.Method.invokeNative(Native Method)
11-28 17:20:05.501: E/AndroidRuntime(1455): at java.lang.reflect.Method.invoke(Method.java:525)
11-28 17:20:05.501: E/AndroidRuntime(1455): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-28 17:20:05.501: E/AndroidRuntime(1455): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-28 17:20:05.501: E/AndroidRuntime(1455): at dalvik.system.NativeStart.main(Native Method)
11-28 17:20:05.501: E/AndroidRuntime(1455): Caused by: java.lang.NullPointerException
11-28 17:20:05.501: E/AndroidRuntime(1455): at com.app.calculadoracalorias.CaloriesCalculator.onCreate(CaloriesCalculator.java:67)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.Activity.performCreate(Activity.java:5133)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-28 17:20:05.501: E/AndroidRuntime(1455): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-28 17:20:05.501: E/AndroidRuntime(1455): ... 11 more
11-28 17:24:42.341: D/AndroidRuntime(1507): Shutting down VM
11-28 17:24:42.341: W/dalvikvm(1507): threadid=1: thread exiting with uncaught exception (group=0x41465700)
11-28 17:24:42.371: E/AndroidRuntime(1507): FATAL EXCEPTION: main
11-28 17:24:42.371: E/AndroidRuntime(1507): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.calculadoracalorias/com.app.calculadoracalorias.CaloriesCalculator}: java.lang.NullPointerException
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.os.Handler.dispatchMessage(Handler.java:99)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.os.Looper.loop(Looper.java:137)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-28 17:24:42.371: E/AndroidRuntime(1507): at java.lang.reflect.Method.invokeNative(Native Method)
11-28 17:24:42.371: E/AndroidRuntime(1507): at java.lang.reflect.Method.invoke(Method.java:525)
11-28 17:24:42.371: E/AndroidRuntime(1507): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-28 17:24:42.371: E/AndroidRuntime(1507): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-28 17:24:42.371: E/AndroidRuntime(1507): at dalvik.system.NativeStart.main(Native Method)
11-28 17:24:42.371: E/AndroidRuntime(1507): Caused by: java.lang.NullPointerException
11-28 17:24:42.371: E/AndroidRuntime(1507): at com.app.calculadoracalorias.CaloriesCalculator.onCreate(CaloriesCalculator.java:70)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.Activity.performCreate(Activity.java:5133)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-28 17:24:42.371: E/AndroidRuntime(1507): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-28 17:24:42.371: E/AndroidRuntime(1507): ... 11 more
最佳答案
如果 btnCalculate 为空，您应该在执行 onclickListener 之前初始化:
btnCalculate = (Button)findViewById(R.id.btnCalculate); //your id
另请注意，您正在初始化 dataAdapter2，但实际上您正在使用 dataAdapert，并且 list2 没有任何元素，因为您声明了它，但您始终填充 list1
关于java.lang.runtimeException 无法启动 Activity componentinfo java.lang.nullpointerException android，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/27196707/