应用程序在android中停止工作

这是我在我的应用程序中的fourthpage类。我收到错误应用程序在android中停止工作

不幸的是应用程序已停止工作

我不知道为什么我会收到这个。

package student.a.a; 

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

import java.text.DecimalFormat; 

public class fourthpage extends Activity { 
    EditText txtb1, txtb2, txtb3, txtb4, txtb5; 
    Button btnper; 
    TextView lblgrade, lblper; 

    DecimalFormat df = new DecimalFormat("##.##"); 

    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.fourthxml); 

     // text boxes 
     txtb1 = (EditText) findViewById(R.id.txtb1); 
     txtb2 = (EditText) findViewById(R.id.txtb2); 
     txtb3 = (EditText) findViewById(R.id.txtb3); 
     txtb4 = (EditText) findViewById(R.id.txtb4); 
     txtb5 = (EditText) findViewById(R.id.txtb5); 

     // buttons 
     btnper = (Button) findViewById(R.id.btnper); 

     // labels/text view 
     lblgrade = (TextView) findViewById(R.id.lblgrade); 
     lblper = (TextView) findViewById(R.id.lblgrade); 
    } 

    String tb1 = txtb1.getText().toString(); 
    String tb2 = txtb2.getText().toString(); 
    String tb3 = txtb3.getText().toString(); 
    String tb4 = txtb4.getText().toString(); 
    String tb5 = txtb5.getText().toString(); 

    double txb1 = Double.parseDouble(tb1); 
    double txb2 = Double.parseDouble(tb2); 
    double txb3 = Double.parseDouble(tb3); 
    double txb4 = Double.parseDouble(tb4); 
    double txb5 = Double.parseDouble(tb5); 

    double sum = 0; 
    double total = 0; 

    public void onClickper(View v) { 
     sum = txb1 + txb2 + txb3 + txb4 + txb5; 
     total = (sum/500) * 100; 
     String tot = df.format(total); 
     lblper.setText(tot); 

     if (total <= 100) { 
      lblgrade.setText("Congratulations !! , Grade 'A+' "); 
     } else if (total <= 80) { 
      lblgrade.setText("Congratulations !! , Grade 'A'"); 
     } else if (total <= 70) { 
      lblgrade.setText("Grade 'B'"); 
     } else if (total <= 60) { 
      lblgrade.setText("Grade 'C'"); 
     } else 
      lblgrade.setText("Failed"); 
    } 
}

这是fourthpage的xml代码。它包含5个文本框，一个按钮和两个textviews：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 

    <TableLayout 
     android:id="@+id/tableLayout1" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <TableRow 
      android:id="@+id/tableRow1" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout1" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/textView1" 
        android:layout_gravity="left" 
        android:text="Calculate your marks" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow7" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout3" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <Space android:layout_gravity="fill_horizontal" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow2" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout2" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/textView2" 
        android:layout_gravity="left" 
        android:text="Subject 1" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

       <EditText 
        android:id="@+id/txtb1" 
        android:layout_width="162dp" 
        android:layout_gravity="fill_horizontal" > 

        <requestFocus /> 
       </EditText> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow3" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/GridLayout01" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/TextView01" 
        android:layout_gravity="left" 
        android:text="Subject 2" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

       <EditText 
        android:id="@+id/txtb2" 
        android:layout_gravity="fill_horizontal" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow4" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/GridLayout02" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/TextView02" 
        android:layout_gravity="left" 
        android:text="Subject 3" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

       <EditText 
        android:id="@+id/txtb3" 
        android:layout_gravity="fill_horizontal" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow5" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/GridLayout03" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/TextView03" 
        android:layout_gravity="left" 
        android:text="Subject 4" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

       <EditText 
        android:id="@+id/txtb4" 
        android:layout_gravity="fill_horizontal" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow6" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/GridLayout04" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/TextView04" 
        android:layout_gravity="left" 
        android:text="Subject 5" 
        android:textAppearance="?android:attr/textAppearanceMedium" /> 

       <EditText 
        android:id="@+id/txtb5" 
        android:layout_gravity="fill_horizontal" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow8" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout4" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 



       <Button 
        android:id="@+id/btnper" 
        android:layout_gravity="left" 
        android:text="Button" android:onClick="onClickper"/> 

       <Button 
        android:id="@+id/btngrade" 
        android:layout_gravity="left" 
        android:text="Button" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow9" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout5" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/textView3" 
        android:layout_gravity="left" 
        android:text="percentage is " 
        android:textAppearance="?android:attr/textAppearanceSmall" /> 

       <TextView 
        android:id="@+id/lblper" 
        android:layout_gravity="left" 
        android:text="Large Text" 
        android:textAppearance="?android:attr/textAppearanceLarge" /> 

      </GridLayout> 

     </TableRow> 

     <TableRow 
      android:id="@+id/tableRow10" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" > 

      <GridLayout 
       android:id="@+id/gridLayout6" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" > 

       <TextView 
        android:id="@+id/textView5" 
        android:layout_gravity="left" 
        android:text=" Grade is   " 
        android:textAppearance="?android:attr/textAppearanceSmall" /> 

       <TextView 
        android:id="@+id/lblgrade" 
        android:layout_gravity="left" 
        android:text="Large Text" 
        android:textAppearance="?android:attr/textAppearanceLarge" /> 

      </GridLayout> 

     </TableRow> 

    </TableLayout> 

</LinearLayout>

这里是AndroidManifest.xml中：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="student.a.a" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk android:minSdkVersion="14" /> 

    <application 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" > 
     <activity 
      android:label="@string/app_name" 
      android:name=".StudentsinfoActivity" > 
      <intent-filter > 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.DEFAULT" /> 
      </intent-filter> 
     </activity> 
     <activity 
      android:label="@string/app_name" 
      android:name=".secondpage" > 
      <intent-filter > 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.DEFAULT" /> 
      </intent-filter> 
     </activity> 
     <activity 
      android:label="@string/app_name" 
      android:name=".thirdpage" > 
      <intent-filter > 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.DEFAULT" /> 
      </intent-filter> 
     </activity> 
     <activity 
      android:label="@string/app_name" 
      android:name=".fourthpage" > 
      <intent-filter > 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 
</manifest>

这里是我的logcat：

08-09 16:32:00.970: W/dalvikvm(892): threadid=1: thread exiting with uncaught exception (group=0x409961f8) 
08-09 16:32:00.980: E/AndroidRuntime(892): FATAL EXCEPTION: main 
08-09 16:32:00.980: E/AndroidRuntime(892): java.lang.RuntimeException: Unable to start activity ComponentInfo{student.a.a/student.a.a.fourthpage}: java.lang.NumberFormatException: Invalid double: "" 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread.access$600(ActivityThread.java:122) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.os.Handler.dispatchMessage(Handler.java:99) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.os.Looper.loop(Looper.java:137) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread.main(ActivityThread.java:4340) 
08-09 16:32:00.980: E/AndroidRuntime(892): at java.lang.reflect.Method.invokeNative(Native Method) 
08-09 16:32:00.980: E/AndroidRuntime(892): at java.lang.reflect.Method.invoke(Method.java:511) 
08-09 16:32:00.980: E/AndroidRuntime(892): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
08-09 16:32:00.980: E/AndroidRuntime(892): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
08-09 16:32:00.980: E/AndroidRuntime(892): at dalvik.system.NativeStart.main(Native Method) 
08-09 16:32:00.980: E/AndroidRuntime(892): Caused by: java.lang.NumberFormatException: Invalid double: "" 
08-09 16:32:00.980: E/AndroidRuntime(892): at java.lang.StringToReal.invalidReal(StringToReal.java:63) 
08-09 16:32:00.980: E/AndroidRuntime(892): at java.lang.StringToReal.parseDouble(StringToReal.java:248) 
08-09 16:32:00.980: E/AndroidRuntime(892): at java.lang.Double.parseDouble(Double.java:295) 
08-09 16:32:00.980: E/AndroidRuntime(892): at student.a.a.fourthpage.onCreate(fourthpage.java:61) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.Activity.performCreate(Activity.java:4465) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
08-09 16:32:00.980: E/AndroidRuntime(892): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) 
08-09 16:32:00.980: E/AndroidRuntime(892): ... 11 more

来源

2015-08-09 Saeed ur Rehman

你可以发布你的logcat的？ – PakkuDon

请添加logcat输出，包括Exception的* Stacktrace *。 –

我已经发布了，请通过它 –

仅仅因为你已经把你的onCreate之后的变量声明并不意味着此代码将在onCreate之后执行。在调用onCreate之前和EditText成员初始化之前，所有String成员都将被初始化。您的double成员也一样。

String tb1 = txtb1.getText().toString(); 
String tb2 = txtb2.getText().toString(); 
String tb3 = txtb3.getText().toString(); 
String tb4 = txtb4.getText().toString(); 
String tb5 = txtb5.getText().toString(); 

double txb1= Double.parseDouble(tb1); 
double txb2= Double.parseDouble(tb2); 
double txb3= Double.parseDouble(tb3); 
double txb4= Double.parseDouble(tb4); 
double txb5= Double.parseDouble(tb5);

你必须移动上述初始化为onCreate和单独声明String和double成员。

... 
String tb1, tb2, tb3, tb4, tb5;  
double txb1, txb2, txb, txb4, txb5; 

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.fourthxml); 

    //text boxes 
    txtb1=(EditText)findViewById(R.id.txtb1); 
    txtb2=(EditText)findViewById(R.id.txtb2); 
    txtb3=(EditText)findViewById(R.id.txtb3); 
    txtb4=(EditText)findViewById(R.id.txtb4); 
    txtb5=(EditText)findViewById(R.id.txtb5); 

    //buttons 
    btnper=(Button)findViewById(R.id.btnper); 

    //labels/text view 
    lblgrade=(TextView)findViewById(R.id.lblgrade); 
    lblper=(TextView)findViewById(R.id.lblgrade); 

    tb1 = txtb1.getText().toString(); 
    tb2 = txtb2.getText().toString(); 
    tb3 = txtb3.getText().toString(); 
    tb4 = txtb4.getText().toString(); 
    tb5 = txtb5.getText().toString(); 

    txb1= Double.parseDouble(tb1); 
    txb2= Double.parseDouble(tb2); 
    txb3= Double.parseDouble(tb3); 
    txb4= Double.parseDouble(tb4); 
    txb5= Double.parseDouble(tb5); 
}

你得到NumberFormatException因为你解析空字符串。如果字符串不包含有效的double值，则可以使用以下方法安全地解析double或将其值设置为某个默认值。

public double getDoubleOrDefault(String value, double defValue) 
{ 
    try 
    { 
     return Double.parseDouble(value); 
    } 
    catch (Exception ex) 
    { 
     return defValue; 
    } 
} 

txb1 = getDoubleOrDefault(tb1, 0.0);

Double.parseDouble documentation

来源

2015-08-09 10:54:39

感谢您的答案，但我仍然得到应用程序停止错误。这里是我的logCat –

谢谢，我得到了我的错误。 :) –

应用程序在android中停止工作

回答

相关问题