Question

我正在尝试将两个EditText相乘，包括editHours和editWage，并在TextView（粗略）中显示结果，非常感谢任何帮助

public class PayrollActivity extends Activity implements OnClickListener {

 TextView gross, net, calculated;
 EditText editHours, editWage;
 int hours, wage, intGross, intNet, pay;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_payroll);


     gross = (TextView) findViewById(R.id.gross);
     hours= Integer.parseInt(editHours.getText().toString());
     wage = Integer.parseInt(editWage.getText().toString());
     gross.setText(hours*wage);
     net = (TextView) findViewById(R.id.net);
     calculated = (TextView) findViewById(R.id.calculated);

        ((Button) findViewById(R.id.addButton)).setOnClickListener(new     OnClickListener() {
         @Override
         public void onClick(View v) {
             // TODO Auto-generated method stub
             StringBuilder str = new StringBuilder("It worked");
             calculated.setText(str);
         }
     });    
    }

该应用程序崩溃

hours= Integer.parseInt(editHours.getText().toString());

logcat的

05-26 14:08:36.591: E/AndroidRuntime(1659): FATAL EXCEPTION: main
05-26 14:08:36.591: E/AndroidRuntime(1659): Process: co.mytms.payroll, PID: 1659
05-26 14:08:36.591: E/AndroidRuntime(1659): java.lang.RuntimeException: Unable to start activity ComponentInfo{co.mytms.payroll/co.mytms.payroll.PayrollActivity}: java.lang.NullPointerException
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.os.Handler.dispatchMessage(Handler.java:102)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.os.Looper.loop(Looper.java:136)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread.main(ActivityThread.java:5017)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at java.lang.reflect.Method.invokeNative(Native Method)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at java.lang.reflect.Method.invoke(Method.java:515)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at dalvik.system.NativeStart.main(Native Method)
05-26 14:08:36.591: E/AndroidRuntime(1659): Caused by: java.lang.NullPointerException
05-26 14:08:36.591: E/AndroidRuntime(1659):     at co.mytms.payroll.PayrollActivity.onCreate(PayrollActivity.java:22)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.Activity.performCreate(Activity.java:5231)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-26 14:08:36.591: E/AndroidRuntime(1659):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-26 14:08:36.591: E/AndroidRuntime(1659):     ... 11 more

Answer 1

有几个问题。

首先在getText() EditText上调用onCreate方法时，它们仍为空（未初始化，请参阅@Manishika answer）。因此Integer.parseInt会尝试解析空String。将其移动到按钮的onClick方法中，这是您想要的行为（即，当您单击它时，它会将EditText的两个值相乘，并将结果设置为{{1} }）。

其次，在执行TextView时，您将调用以gross.setText(hours*wage);为参数的setText方法。 Android系统会尝试加载其内容与您在int文件中定义的ID相对应的适当String。您需要调用接受strings.xml作为参数的方法。 CharSequence

也是如此

此外，在您的问题中添加堆栈跟踪总是很好，因为它可以帮助其他人更快地找到您的错误。

希望它有所帮助！：）

Answer 2

在从他们那里获取文本之前，您还没有初始化EditTexts

editHours = (EditText)findViewById(R.id.editHours_id);
editWage = (EditText)findViewById(R.id.editWage_id);

并且还将你的计算放在onClick上，因为它最初只返回空字符串。

 ((Button) findViewById(R.id.addButton)).setOnClickListener(new     OnClickListener() {
             @Override
             public void onClick(View v) {

//If your input contains decimal values also then use BigDecimal() 
//Following code will work for both int and decimal values
gross.setText(""+new BigDecimal(editHours.getText()
                        .toString()).multiply(new BigDecimal(editWage.getText()
                        .toString())));
                 StringBuilder str = new StringBuilder("It worked");
                 calculated.setText(str);



             }
         });

将两个编辑文本相乘

2 个答案: