我正在为明天到期的移动应用开发最终项目开发一个 android 应用程序，但遇到了问题。直到昨天，我的应用程序都可以在我的手机上正常运行，但从那时起我就以某种方式搞砸了。该程序运行完美，并在模拟器上执行我需要的所有操作，即使是在我从昨天开始添加的所有内容之后，所以我认为该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，发现该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);
}
}
自昨天以来我唯一添加的是在“eMilesDriven”变量上设置的 TextWatcher，它将进行计算。我唯一能想到的另一件事是我今天更改了我的启动器图标，但是应用程序中的其他所有内容都可以正常工作，所以我不确定是这样。我只是不明白为什么它在我的模拟器上完美运行并在我的手机上崩溃。我已经多次重新启动 Android Studio，并从我的手机上删除了该应用程序并尝试再次启动它，但每次它都没有为我提供 logcat 错误。我很感激我能得到的任何帮助。如果我不能在明天之前解决它，我可能只需要在模拟器上展示我的应用程序，但我真的很想知道它为什么崩溃。
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)
获取当前焦点（）
返回当前具有焦点的此 Window 中的视图，如果没有，则返回 null。请注意，这不会在任何包含窗口中查找。
删除 getCurrentFocus() 因为它会返回 null ..
我所看到的，你所做的afterTextChanged(Editable s)是它已经指向当前的edittext ..
其他可能的空指针在这里
if (ratePerMile.equals("") && !ratePerDelivery.equals(""))
改成
if (ratePerMile == null && ratePerDelivery != null)
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