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java - 如何使用纯文本获取输入？

问题描述

firstNumber并且secondNumber是 EditText 类型。我试图从firstNumberand获取值secondNumber并将它们转换为 type float，但是当我这样做时，我得到一个 Exception java.lang.NumberFormatException，我无法找到问题的解决方案。请帮忙。

这是代码

firstNumber = (EditText)findViewById(R.id.firstNumber);
secondNumber = (EditText)findViewById(R.id.secondNumber);
result = (TextView)findViewById(R.id.result);
s1 = firstNumber.getText().toString();
s2 = secondNumber.getText().toString();
num1 = Float.parseFloat(s1);
num2 = Float.parseFloat(s2);

我得到的 Logcat 是-

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.calcmpttos, PID: 17846
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.calcmpttos/com.example.calcmpttos.MainActivity}: java.lang.NumberFormatException: For input string: "Enter First Number"
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
 Caused by: java.lang.NumberFormatException: For input string: "Enter First Number"
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
    at sun.misc.FloatingDecimal.parseFloat(FloatingDecimal.java:122)
    at java.lang.Float.parseFloat(Float.java:451)
    at com.example.calcmpttos.MainActivity.onCreate(MainActivity.java:39)
    at android.app.Activity.performCreate(Activity.java:7136)
    at android.app.Activity.performCreate(Activity.java:7127)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6669) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
2019-07-07 20:29:53.693 17846-17846/com.example.calcmpttos I/Process: Sending signal. PID: 17846 SIG: 9

标签： javaandroid

解决方案

你不能只抛出一个不包含可解析浮点数的字符串来解析浮点数并期望它解析它，这就是你得到 NumberFormatException 的原因。

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