将两个编辑文本相乘[重复]

Question

我正在尝试将两个EditText相乘，两个editthours和editWage并在TextView（gross）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);
         }
     });    
    }

该应用程序崩溃于

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

logcat

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oncreate中调用edittext的gettext()方法时，它们仍然是空的（并且未初始化，请参阅@manishika答案）。因此integer.parseint将尝试解析空的字符串。将其移动到按钮的onclick方法中，这就是您想要的行为（即当您单击它时，它将edittext的两个值相乘，并将结果设置为textview)。

其次，在执行gross.setText(Hours*Walge)；时，您将调用setText方法，该方法将int作为参数。Android系统将尝试加载相应的String，其id与您在Strings.xml文件中定义的id相对应。您需要调用接受charSequence作为参数的方法。gross.settext(string.valueof（小时*工资））；也是如此

此外，在问题中添加stacktrace总是很好的，因为它可以帮助其他人更快地发现您的错误。

希望有帮助！：）