顯示NumberFormat異常無效的雙重

Question

我想使用一些可編輯文本在Double格式中獲得一些值。

將edittext值轉換爲double時，顯示爲number precision error。

我activity.xml：

<EditText 
     android:id="@+id/edit1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_above="@+id/textView1" 
     android:layout_alignRight="@+id/textView1" 
     android:layout_marginBottom="57dp" 
     android:layout_marginRight="31dp" 
     android:ems="10" 
     android:inputType="number" > 

    </EditText> 

和我mainactivity代碼我試圖

檢索來自的EditText的雙重價值，但顯示

NumberFormatException的無效雙：

package com.example.habijabi; 

import android.os.Bundle; 
import android.app.Activity; 
import android.view.Menu; 
import android.widget.EditText; 
import android.widget.TextView; 

public class MainActivity extends Activity { 

    EditText et,et1; 
    TextView t; 

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


     et=(EditText)findViewById(R.id.edit1); 
     String s=et.getText().toString(); 
     double data; 
     data=Double.parseDouble(s); 
     System.out.println(s); 



    } 


} 

顯示這logcat的：

11-25 14:07:13.386: I/Process(1105): Sending signal. PID: 1105 SIG: 9 
11-25 14:07:14.797: W/Trace(1170): Unexpected value from nativeGetEnabledTags: 0 
11-25 14:07:14.797: W/Trace(1170): Unexpected value from nativeGetEnabledTags: 0 
11-25 14:07:14.906: W/Trace(1170): Unexpected value from nativeGetEnabledTags: 0 
11-25 14:07:14.906: W/Trace(1170): Unexpected value from nativeGetEnabledTags: 0 
11-25 14:07:15.256: D/AndroidRuntime(1170): Shutting down VM 
11-25 14:07:15.256: W/dalvikvm(1170): threadid=1: thread exiting with uncaught exception (group=0x40a70930) 
11-25 14:07:15.286: E/AndroidRuntime(1170): FATAL EXCEPTION: main 
11-25 14:07:15.286: E/AndroidRuntime(1170): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.habijabi/com.example.habijabi.MainActivity}: java.lang.NumberFormatException: Invalid double: "" 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.os.Handler.dispatchMessage(Handler.java:99) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.os.Looper.loop(Looper.java:137) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread.main(ActivityThread.java:5039) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at java.lang.reflect.Method.invoke(Method.java:511) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at dalvik.system.NativeStart.main(Native Method) 
11-25 14:07:15.286: E/AndroidRuntime(1170): Caused by: java.lang.NumberFormatException: Invalid double: "" 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at java.lang.StringToReal.invalidReal(StringToReal.java:63) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at java.lang.StringToReal.parseDouble(StringToReal.java:248) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at java.lang.Double.parseDouble(Double.java:295) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at com.example.habijabi.MainActivity.onCreate(MainActivity.java:27) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.Activity.performCreate(Activity.java:5104) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
11-25 14:07:15.286: E/AndroidRuntime(1170):  ... 11 more 

Answer 1

的原因是，""不是有效的兩倍。你需要測試前的字符串或捕捉這些異常

double data; 

try { 
    data = new Double(et.getText().toString()); 
} catch (NumberFormatException e) { 
    data = 0; // your default value 
} 

重要的一點：添加try and catch當你鑄造任何東西。