Android，无效的双：“”空白字段使程序崩溃[重复]

Question

在用户输入后，我正在尝试使用按钮进行计算。当我不填写字段并按下按钮时，我的程序崩溃了，但我只想敬酒..我已经阅读了很多其他类似的问题，但我不明白我必须做些什么来解决在我的代码中.. 有没有人可以帮助我？？谢谢。。

activity_main.xml：

<EditText
    android:layout_width="130dp"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText1"/>

<EditText
    android:layout_width="130dp"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText2"/>

<EditText
    android:layout_width="130dp"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText3"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text=""
    android:id="@+id/textView1"/>

<Button
    android:layout_width="65dp"
    android:layout_height="wrap_content"
    android:id="@+id/calculateButton
    android:background="@android:drawable/ic_menu_edit" />

MainActivity.java:

......
mEditText1 = (EditText)findViewById(R.id.editText1);
mEditText2 = (EditText)findViewById(R.id.editText2);
mEditText3 = (EditText)findViewById(R.id.editText3);
mTextView = (TextView)findViewById(R.id.textView1);
cButton =  (Button)findViewById(R.id.calculateButton);
    cButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //When the button is clicked, call the calucate method.
            calculate();
        }
    });

......

public void calculate(){

    Double value1 = Double.parseDouble(mEditText1.getText().toString());
    Double value2 = Double.parseDouble(mEditText2.getText().toString());
    Double value3 = Double.parseDouble(mEditText3.getText().toString());
    if((value1!=0)&&(value2!=0)) {

        if ((value1 != null) && (value2 != null) && (value3 != null)) {
            calculatedValue = (value2 * value3) / value1;
            mTextView.setText(calculatedValue.toString());}
    else {
            Toast.makeText(getApplicationContext(), "Please fill them all", Toast.LENGTH_LONG).show();
          }
 }

我得到的错误是：

12-22 20:09:26.694 18523-18523/com.example.nigi.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.NumberFormatException: Invalid double: ""
    at java.lang.StringToReal.invalidReal(StringToReal.java:63)
    at java.lang.StringToReal.parseDouble(StringToReal.java:248)
    at java.lang.Double.parseDouble(Double.java:295)
    at android.view.View.performClick(View.java:4442)
    at android.view.View$PerformClick.run(View.java:18473)
    at android.os.Handler.handleCallback(Handler.java:733)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:136)
    at android.app.ActivityThread.main(ActivityThread.java:5105)

谢谢！！

Answer 1

使用此代码：

    public void calculate()
{        
        if(String.valueOf(mEditText1.getText()).length() == 0)    
        mEditText1.setError("Required only alphabets");    
        else if(String.valueOf(mEditText2.getText()).length() == 0)    
        mEditText2.setError("Required only alphabets");    
        else if(String.valueOf(mEditText3.getText()).length() == 0)
            mEditText3.setError("Required only alphabets");    
        else{
        Double value1 = Double.parseDouble(String.valueOf(mEditText1.getText()));
        Double value2 = Double.parseDouble(String.valueOf(mEditText2.getText()));
        Double value3 =    Double.parseDouble(String.valueOf(mEditText3.getText()));
        calculatedValue = (value2 * value3) / value1;
        mTextView.setText(calculatedValue.toString());
       }
 }