我正在Android中创建一个单位转换应用程序，其中一个可以轻松地将单位更改为特定类型，基本单位是TeaSpoons，我正在使用Android Studio IDE，但是当我运行我的项目时，它运行正常没有任何问题，但在我的应用程序内部，当我选择其他测量单位时，它会崩溃并且“不幸的是，单位转换应用程序停止了”对话框弹出并关闭应用程序..
检查Logcat后发现有NullPointerException，我无法修复它 我提供下面的源代码和发生异常的代码行，请帮助我解决这个问题，并建议我更好的解决方案。
package com.hackercoder.samsung.unitconversion;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
private Spinner unitTypeSpinner;
private EditText amountTypeText;
private TextView TeaSpoontv,Cupstv,TableSpoontv,Ouncestv,Kilogramtv,Quarttv,Gallontv,Poundtv,Millilitretv,
Litretv,Milligramtv, Pinttv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addItemsToUnitTypeSpinner();
addListenerToUnitTypeSpinner();
amountTypeText=(EditText)findViewById(R.id.amount_entered);
initializeTextViews();
}
public void initializeTextViews()
{
TeaSpoontv=(TextView)findViewById(R.id.tsp_text_view);
Cupstv=(TextView)findViewById(R.id.cups_text_view);
TableSpoontv=(TextView)findViewById(R.id.tbsp_text_view);
Ouncestv=(TextView)findViewById(R.id.oz_text_view);
Kilogramtv=(TextView)findViewById(R.id.kg_text_view);
Quarttv=(TextView)findViewById(R.id.quart_text_view);
Gallontv=(TextView)findViewById(R.id.gallon_text_view);
Poundtv=(TextView)findViewById(R.id.pound_text_view);
Millilitretv=(TextView)findViewById(R.id.ml_text_view);
Litretv=(TextView)findViewById(R.id.litre_text_view);
Milligramtv=(TextView)findViewById(R.id.mlg_text_view);
Pinttv=(TextView)findViewById(R.id.pint_text_view);
}
public void addItemsToUnitTypeSpinner()
{
unitTypeSpinner=(Spinner)findViewById(R.id.unit_type_spinner);
ArrayAdapter<CharSequence> unitTypeSpinnerAdapter= ArrayAdapter.createFromResource(this,R.array.conversion_types,android.R.layout.simple_spinner_item);
unitTypeSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
unitTypeSpinner.setAdapter(unitTypeSpinnerAdapter);
}
public void addListenerToUnitTypeSpinner() {
unitTypeSpinner = (Spinner) findViewById(R.id.unit_type_spinner);
unitTypeSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String itemSelectedInSpinner = parent.getItemAtPosition(position).toString();
checkIfConvertingFromTeaSpoon(itemSelectedInSpinner);
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
public void checkIfConvertingFromTeaSpoon(String currentUnit) {
if (currentUnit!=null)
{
switch (currentUnit) {
case "TeaSpoon":
updateUnitTypeUsingTSP(Quantity.Unit.tsp);
break;
case "TableSpoon":
updateUnitTypeUsingOther(Quantity.Unit.tbs);
break;
case "Cups":
updateUnitTypeUsingOther(Quantity.Unit.cup);
break;
case "Ounces":
updateUnitTypeUsingOther(Quantity.Unit.oz);
break;
case "Kilogram":
updateUnitTypeUsingOther(Quantity.Unit.kg);
break;
case "Quart":
updateUnitTypeUsingOther(Quantity.Unit.quart);
break;
case "Gallon":
updateUnitTypeUsingOther(Quantity.Unit.gallon);
break;
case "Pound":
updateUnitTypeUsingOther(Quantity.Unit.pound);
break;
case "Millilitre":
updateUnitTypeUsingOther(Quantity.Unit.ml);
break;
case "Litre":
updateUnitTypeUsingOther(Quantity.Unit.liter);
break;
case "Milligram":
updateUnitTypeUsingOther(Quantity.Unit.mg);
break;
case "Pint":
updateUnitTypeUsingOther(Quantity.Unit.pint);
break;
}
}
}
public void updateUnitTypeUsingTSP(Quantity.Unit currentUnit)
{
double doubleToConvert= Double.parseDouble(amountTypeText.getText().toString());
String teaspoonValueAndUnit= doubleToConvert + " " + "TeaSpoon";
TeaSpoontv.setText(teaspoonValueAndUnit);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.tbs,TableSpoontv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.cup,Cupstv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.oz,Ouncestv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.kg,Kilogramtv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.quart,Quarttv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.gallon,Gallontv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.pound,Poundtv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.ml,Millilitretv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.liter,Litretv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.mg,Milligramtv);
updateUnitTextFieldUsingTSP(doubleToConvert,Quantity.Unit.pint,Pinttv);
}
public void updateUnitTextFieldUsingTSP(double doubleToConvert, Quantity.Unit unitConvertingTo, TextView tv) {
Quantity unitQuantity= new Quantity(doubleToConvert,Quantity.Unit.tsp);
String tempUnit= unitQuantity.to(unitConvertingTo).toString();
tv.setText(tempUnit);
}
public void updateUnitTypeUsingOther(Quantity.Unit currentUnitInSpinner) {
double doubleToConvert= Double.parseDouble(amountTypeText.getText().toString());
Quantity currentQuantitySelected= new Quantity(doubleToConvert, currentUnitInSpinner);
String valueInTSP= currentQuantitySelected.to(Quantity.Unit.tsp).toString();
TeaSpoontv.setText(valueInTSP);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.tbs, TableSpoontv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.cup,Cupstv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.oz,Ouncestv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.kg,Kilogramtv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.quart,Quarttv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.gallon,Gallontv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.pound,Poundtv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.ml,Millilitretv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.liter,Litretv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.mg,Milligramtv);
updateUnitTextFieldUsingTSP(doubleToConvert,currentUnitInSpinner,Quantity.Unit.pint,Pinttv);
if(currentUnitInSpinner.name().equals(currentQuantitySelected.unit.name()))
{
String currentSelectedUnitInSpinnerTextInTextView= doubleToConvert + " " + currentQuantitySelected.unit.name();
String currentTextViewName= currentQuantitySelected.unit.name()+" _text_view";
int currentID=getResources().getIdentifier(currentTextViewName,"id",MainActivity.this.getPackageName());
TextView textview=(TextView)findViewById(currentID);
textview.setText(currentTextViewName);
}
}
public void updateUnitTextFieldUsingTSP(double doubleToConvert, Quantity.Unit currentUnitInSpinner, Quantity.Unit preferredUnit, TextView targetTextView)
{
Quantity currentQuantitySelected=new Quantity(doubleToConvert, currentUnitInSpinner);
String updatedTextviewText =currentQuantitySelected.to(Quantity.Unit.tsp).to(preferredUnit).toString();
targetTextView.setText(updatedTextviewText);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
和生成的logcat
02-04 13:16:44.395 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ Late-enabling CheckJNI
02-04 13:16:44.395 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ Try to disable coredump for pid 18606
02-04 13:16:44.395 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ Process 18606 nice name: com.hackercoder.samsung.unitconversion
02-04 13:16:44.395 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ Extra Options: not specified
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion I/dalvikvm﹕ Could not find method android.view.ViewGroup.onNestedScrollAccepted, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onNestedScrollAccepted
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ VFY: unable to resolve virtual method 11345: Landroid/view/ViewGroup;.onNestedScrollAccepted (Landroid/view/View;Landroid/view/View;I)V
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ VFY: replacing opcode 0x6f at 0x0000
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion I/dalvikvm﹕ Could not find method android.view.ViewGroup.onStopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onStopNestedScroll
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ VFY: unable to resolve virtual method 11351: Landroid/view/ViewGroup;.onStopNestedScroll (Landroid/view/View;)V
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ VFY: replacing opcode 0x6f at 0x0000
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion I/dalvikvm﹕ Could not find method android.support.v7.internal.widget.ActionBarOverlayLayout.stopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.setHideOnContentScrollEnabled
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ VFY: unable to resolve virtual method 9039: Landroid/support/v7/internal/widget/ActionBarOverlayLayout;.stopNestedScroll ()V
02-04 13:16:44.475 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x000e
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ VFY: unable to resolve virtual method 364: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ VFY: unable to resolve virtual method 386: Landroid/content/res/TypedArray;.getType (I)I
02-04 13:16:44.485 18606-18606/com.hackercoder.samsung.unitconversion D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
02-04 13:16:44.525 18606-18606/com.hackercoder.samsung.unitconversion D/TextView﹕ Constructor - Got Res id for appearance for textColorPrimaryInverse
02-04 13:16:44.525 18606-18606/com.hackercoder.samsung.unitconversion W/ResourceType﹕ Skipping entry 0x7f070035 in package table 0 because it is not complex!
02-04 13:16:44.525 18606-18606/com.hackercoder.samsung.unitconversion D/TextView﹕ Constructor - Got appearance for textColorPrimaryInverse
02-04 13:16:44.525 18606-18606/com.hackercoder.samsung.unitconversion D/TextView﹕ Constructor -- Got mEditTextBackgroundColor
02-04 13:16:44.605 18606-18606/com.hackercoder.samsung.unitconversion D/android.widget.GridLayout﹕ horizontal constraints: x1-x0>=341, x2-x1>=276, x2-x0<=596 are inconsistent; permanently removing: x2-x0<=596.
02-04 13:16:44.635 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 46
02-04 13:16:44.635 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 49
02-04 13:16:44.635 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 50
02-04 13:16:44.645 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 50
02-04 13:16:44.645 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 50
02-04 13:16:44.655 18606-18606/com.hackercoder.samsung.unitconversion E/IMGSRV﹕ :0: PVRDRMOpen: TP3, ret = 52
02-04 13:16:44.675 18606-18606/com.hackercoder.samsung.unitconversion D/OpenGLRenderer﹕ Enabling debug mode 0
02-04 13:16:50.035 18606-18606/com.hackercoder.samsung.unitconversion D/AndroidRuntime﹕ Shutting down VM
02-04 13:16:50.035 18606-18606/com.hackercoder.samsung.unitconversion W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x430ef140)
**02-04 13:16:50.035 18606-18606/com.hackercoder.samsung.unitconversion E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.hackercoder.samsung.unitconversion, PID: 18606
java.lang.NullPointerException
at com.hackercoder.samsung.unitconversion.MainActivity.updateUnitTypeUsingOther(MainActivity.java:170)
at com.hackercoder.samsung.unitconversion.MainActivity.checkIfConvertingFromTeaSpoon(MainActivity.java:86)
at com.hackercoder.samsung.unitconversion.MainActivity$1.onItemSelected(MainActivity.java:64)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:893)
at android.widget.AdapterView.access$200(AdapterView.java:48)
at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:861)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:149)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)**
根据Logcat，updateUnitTypeusingOther（）
中发生异常请帮我解决问题或建议我提供更好的解决方案