我正在开发一个即将到期的移动应用开发最终项目的Android应用程序，并且遇到了问题。直到昨天，我的应用程序将在我的手机上正常运行，但我从那时起以某种方式弄乱了一些东西。该程序运行完美，并在模拟器上完成我需要的所有内容，即使在我从昨天开始添加的所有内容之后，所以我认为应用程序已完全完成并准备好呈现。但是，我今天在手机上运行它，发现应用程序在启动以下活动时崩溃...
public class OrderDetails extends AppCompatActivity {
private List<PhoneBook> contactList;
private ListView listView;
private TextView name, number, address, orderTotal, amountReceived, tip, mileage, grandTotal;
private Button add;
private PhonebookAdapter adapter;
PhoneBookHandler db;
double dAmountReceived;
double dTotalCost;
double dSubtract;
double dMileage;
double dGrandTotal;
double dTip;
double dAdd;
double dMilesDriven;
double dMultiply;
double dRatePerMile;
String sAmountReceived;
String sTotalCost;
String sTip;
String sMileage;
String sGrandTotal;
String sAddress;
String ratePerDelivery;
String ratePerMile;
String milesDriven;
EditText eAmountReceived;
EditText eTotalCost;
EditText eTip;
EditText eMileage;
EditText eAddress;
EditText eGrandTotal;
EditText eMilesDriven;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.order_details);
listView = (ListView) findViewById(R.id.contactlist);
db = new PhoneBookHandler(this);
contactList = db.getAllContacts();
adapter = new PhonebookAdapter(this, contactList);
eAddress = (EditText) findViewById(R.id.address);
eTotalCost = (EditText) findViewById(R.id.orderTotal);
eAmountReceived = (EditText) findViewById(R.id.amountReceived);
eTip = (EditText) findViewById(R.id.tip);
eMileage = (EditText) findViewById(R.id.mileage);
eGrandTotal = (EditText) findViewById(R.id.grandTotal);
eMilesDriven = (EditText) findViewById(R.id.milesDriven);
// use shared preferences to inflate mileage edittext with data entered in settings menu
ratePerDelivery = PreferenceManager.getDefaultSharedPreferences(this).getString("ratePerDeliveryPref", null);
ratePerMile = PreferenceManager.getDefaultSharedPreferences(this).getString("ratePerMilePref", null);
eAmountReceived.addTextChangedListener(new TextWatcher()
{
@Override
public void beforeTextChanged(CharSequence s, int start,
int count, int after){}
@Override
public void onTextChanged(CharSequence s, int start,
int before, int count){}
@Override
public void afterTextChanged(Editable s)
{
if (getCurrentFocus() == eAmountReceived)
{
sAmountReceived = eAmountReceived.getText().toString();
sTotalCost = eTotalCost.getText().toString();
sMileage = eMileage.getText().toString();
sTip = eTip.getText().toString();
try
{
dAmountReceived = Double.parseDouble(sAmountReceived);
dTotalCost = Double.parseDouble(sTotalCost);
dSubtract = dAmountReceived - dTotalCost;
dMileage = Double.parseDouble(sMileage);
dGrandTotal = dSubtract + dMileage;
} catch(NumberFormatException e){}
sTip = String.valueOf(dSubtract);
DecimalFormat df = new DecimalFormat("0.00");
sTip = df.format(dSubtract);
eTip.setText(sTip);
sGrandTotal = String.valueOf(dGrandTotal);
sGrandTotal = df.format(dGrandTotal);
eGrandTotal.setText(sGrandTotal);
}
}
});
eTip.addTextChangedListener(new TextWatcher()
{
@Override
public void beforeTextChanged(CharSequence s, int start,
int count, int after){}
@Override
public void onTextChanged(CharSequence s, int start,
int before, int count){}
@Override
public void afterTextChanged(Editable s) {
if (getCurrentFocus() == eTip)
{
sAmountReceived = eAmountReceived.getText().toString();
sTotalCost = eTotalCost.getText().toString();
sMileage = eMileage.getText().toString();
sTip = eTip.getText().toString();
try {
dTip = Double.parseDouble(sTip);
dTotalCost = Double.parseDouble(sTotalCost);
dAdd = dTotalCost + dTip;
dMileage = Double.parseDouble(sMileage);
dGrandTotal = dTip + dMileage;
} catch (NumberFormatException e) {
}
sAmountReceived = String.valueOf(dAdd);
DecimalFormat df = new DecimalFormat("0.00");
sAmountReceived = df.format(dAdd);
eAmountReceived.setText(sAmountReceived);
sGrandTotal = String.valueOf(dGrandTotal);
sGrandTotal = df.format(dGrandTotal);
eGrandTotal.setText(sGrandTotal);
}
}
});
if (ratePerMile.equals("") && !ratePerDelivery.equals(""))
{
eMileage.setText(ratePerDelivery);
}
else
{
eMilesDriven.addTextChangedListener(new TextWatcher()
{
@Override
public void beforeTextChanged(CharSequence s, int start,
int count, int after){}
@Override
public void onTextChanged(CharSequence s, int start,
int before, int count){}
@Override
public void afterTextChanged(Editable s)
{
if (getCurrentFocus() == eMilesDriven)
{
sAmountReceived = eAmountReceived.getText().toString();
sTotalCost = eTotalCost.getText().toString();
sMileage = eMileage.getText().toString();
sTip = eTip.getText().toString();
try
{
milesDriven = eMilesDriven.getText().toString();
dMilesDriven = Double.parseDouble(milesDriven);
dRatePerMile = Double.parseDouble(ratePerMile);
dMultiply = dRatePerMile * dMilesDriven;
dGrandTotal = dSubtract + dMultiply;
} catch(NumberFormatException e){}
sMileage = String.valueOf(dMultiply);
DecimalFormat df = new DecimalFormat("0.00");
sMileage = df.format(dMultiply);
eMileage.setText(sMileage);
sGrandTotal = String.valueOf(dGrandTotal);
sGrandTotal = df.format(dGrandTotal);
eGrandTotal.setText(sGrandTotal);
}
}
});
}
}
public void onClick(View view)
{
name = (EditText) findViewById(R.id.name);
number = (EditText) findViewById(R.id.number);
address = (EditText) findViewById(R.id.address);
orderTotal = (EditText) findViewById(R.id.orderTotal);
amountReceived = (EditText) findViewById(R.id.amountReceived);
tip = (EditText) findViewById(R.id.tip);
mileage = (EditText) findViewById(R.id.mileage);
grandTotal = (EditText) findViewById(R.id.grandTotal);
String cName = name.getText().toString();
String num = number.getText().toString();
String cAddress = address.getText().toString();
String cOrderTotal = orderTotal.getText().toString();
String cAmountReceived = amountReceived.getText().toString();
String cTip = tip.getText().toString();
String cMileage = mileage.getText().toString();
String cGrandTotal = grandTotal.getText().toString();
int id = db.addContact(new PhoneBook(cName, num, cAddress, cOrderTotal,
cAmountReceived, cTip, cMileage, cGrandTotal));
contactList.add(new PhoneBook(id, cName, num, cAddress, cOrderTotal,
cAmountReceived, cTip, cMileage, cGrandTotal));
adapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), "Entry Successfully Created.", Toast.LENGTH_LONG).show();
}
public void buttonClickFunction(View v)
{
Intent intent = new Intent(getApplicationContext(), display_database.class);
startActivity(intent);
}
public void sendMessage(View v)
{
eAddress = (EditText) findViewById(R.id.address);
sAddress = eAddress.getText().toString();
String map = "http://maps.google.com/maps?q=" + sAddress;
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(map));
startActivity(intent);
}
}
我昨天唯一添加的是TextWatcher，它设置在＆＃34; eMilesDriven＆＃34;将进行计算的变量。我能想到的另一件事就是今天我改变了我的启动器图标，但是应用程序中的其他所有内容都正常工作，所以我不确定是不是这样。我只是不明白为什么它在我的模拟器上完美运行并且在我的手机上崩溃。我已经多次重启Android Studio，并从我的手机上删除了应用程序并尝试再次启动它，但每次都没有给我提供任何logcat错误。我将不胜感激任何帮助。如果我明天无法解决问题，我可能只需要在模拟器上展示我的应用程序，但我真的想知道它为什么会崩溃。
编辑： logcat错误如下：
FATAL EXCEPTION: main
Process: com.example.boley.databaseexample, PID: 15335
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.boley.databaseexample/com.example.boley.personaldeliveryassistant.OrderDetails}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3253)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3349)
at android.app.ActivityThread.access$1100(ActivityThread.java:221)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at com.example.boley.personaldeliveryassistant.OrderDetails.onCreate(OrderDetails.java:173)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3206)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3349)
at android.app.ActivityThread.access$1100(ActivityThread.java:221)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
答案 0 :(得分：2)
getCurrentFocus（）
返回此窗口中当前具有焦点的视图，如果是，则返回null 没有了。请注意，这不包含任何包含Window的内容。
删除getCurrentFocus（），因为它将返回null ..
我所看到的，你在afterTextChanged(Editable s)中做的，它已经指向当前的edittext ..
其他posible null指针在这里
if (ratePerMile.equals("") && !ratePerDelivery.equals(""))
更改为
if (ratePerMile == null && ratePerDelivery != null)