RadioGroup导致Android App崩溃？

Question

I'm trying to build an app in Android Studio that calculates the local sales tax based on the purchase amount entered by the user. However I think my radio groups are causing the app to crash because when I remove all references to them, the app opens just fine.

I checked the XML code and the IDE didn't give me any warnings other than using literal strings for naming conventions.

When I run the program, I get a message in the emulator saying "Unfortunately, week3app has stopped." No error that I can see shows up in the stack trace when I run the app unless it's one I'm unfamiliar with and I'm just not seeing it. Here is my code:

XML Layout:

<?XML version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.eliza.week3app.Main"
    tools:showIn="@layout/activity_main"
    android:background="#ebe8e8">

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/zipEdit"
        android:textSize="12sp"
        android:hint="12345"
        android:layout_alignParentTop="true"
        android:layout_alignLeft="@+id/findButton"
        android:layout_alignStart="@+id/findButton"
        android:layout_marginTop="33dp"
        android:layout_toStartOf="@+id/purchAmtEdit"
        android:layout_alignRight="@+id/findButton"
        android:layout_alignEnd="@+id/findButton" />


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Find Tax"
        android:id="@+id/findButton"
        android:layout_marginTop="53dp"
        android:layout_below="@+id/AmountLbl"
        android:layout_toRightOf="@+id/totalLbl"
        android:layout_toEndOf="@+id/totalLbl" />

    <RadioGroup
        android:checkedButton="@+id/gpsRadio"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/radioGroup1"
        android:layout_alignParentTop="true"
        android:layout_toLeftOf="@+id/zipEdit"
        android:layout_toStartOf="@+id/zipEdit"
        android:layout_alignBottom="@+id/zipEdit">

        <RadioButton
        android:layout_width="124dp"
        android:layout_height="wrap_content"
        android:text="Use GPS"
        android:id="@+id/gpsRadio"
        android:textSize="12sp"
        android:layout_marginLeft="20sp" />

        <RadioButton
            android:layout_width="124sp"
            android:layout_height="wrap_content"
            android:text="Use Zip"
            android:id="@+id/zipRadio"
            android:textSize="12sp"
            android:layout_below="@+id/gpsRadio"
            android:layout_marginLeft="20sp"/>

    </RadioGroup>

    <RadioGroup
        android:checkedButton="@+id/generalRadio"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/radioGroup2"
        android:layout_below="@+id/zipEdit"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">


    <RadioButton
        android:layout_width="124sp"
        android:layout_height="wrap_content"
        android:text="General Tax"
        android:id="@+id/generalRadio"
        android:textSize="12sp"
        android:layout_marginTop="31sp"
        android:layout_marginLeft="22sp"
        android:layout_marginStart="22sp"/>

    <RadioButton
        android:layout_width="124dp"
        android:layout_height="wrap_content"
        android:layout_marginLeft="22sp"
        android:text="Grocery Tax"
        android:id="@+id/groceryRadio"
        android:textSize="12sp"/>

    </RadioGroup>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Purchase Amount"
        android:id="@+id/AmountLbl"
        android:textColor="#030000"
        android:layout_below="@+id/radioGroup2"
        android:layout_toLeftOf="@+id/purchAmtEdit"
        android:layout_toStartOf="@+id/purchAmtEdit"
        android:layout_marginTop="29dp" />

    <EditText
        android:layout_width="130sp"
        android:layout_height="wrap_content"
        android:textSize="12sp"
        android:inputType="numberDecimal"
        android:ems="10"
        android:id="@+id/purchAmtEdit"
        android:layout_above="@+id/findButton"
        android:layout_toRightOf="@+id/radioGroup2"
        android:layout_toEndOf="@+id/radioGroup2"
        android:layout_marginLeft="32dp"
        android:layout_marginStart="32dp" />

    <TextView
        android:layout_marginTop="85dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tax Amount: "
        android:id="@+id/taxAmountLbl"
        android:textColor="#030000"
        android:layout_below="@+id/findButton"
        android:layout_alignLeft="@+id/AmountLbl"
        android:layout_alignStart="@+id/AmountLbl" />

    <TextView
        android:layout_marginTop="28dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Total Amount: "
        android:id="@+id/totalLbl"
        android:textColor="#030000"
        android:layout_below="@+id/taxAmountLbl"
        android:layout_alignLeft="@+id/taxAmountLbl"
        android:layout_alignStart="@+id/taxAmountLbl" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/taxAmtResultLbl"
        android:textColor="#030000"
        android:layout_above="@+id/totalLbl"
        android:layout_toRightOf="@+id/totalLbl"
        android:layout_toEndOf="@+id/totalLbl" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/totalAmtResultLbl"
        android:textColor="#030000"
        android:layout_alignBottom="@+id/taxAmountLbl"
        android:layout_toRightOf="@+id/taxAmtResultLbl"
        android:layout_toEndOf="@+id/taxAmtResultLbl" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Location: "
        android:id="@+id/locationLbl"
        android:textColor="#030000"
        android:layout_marginBottom="27dp"
        android:layout_above="@+id/taxAmtResultLbl"
        android:layout_alignLeft="@+id/taxAmountLbl"
        android:layout_alignStart="@+id/taxAmountLbl" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/locResultsLbl"
        android:textColor="#030000"
        android:layout_alignBottom="@+id/locationLbl"
        android:layout_toRightOf="@+id/locationLbl"
        android:layout_toEndOf="@+id/locationLbl"/>   

</RelativeLayout>

Main Class:

    package com.example.eliza.week3app;    
    import android.app.Activity;
    import android.os.Bundle;
    import android.support.design.widget.FloatingActionButton;
    import android.support.design.widget.Snackbar;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
    import android.view.View;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.widget.EditText;
    import android.widget.RadioButton;
    import android.widget.RadioGroup;

    public class Main extends Activity {
    public RadioButton gpsRadio, zipRadio, genTaxRadio, grocTaxRadio;
    public EditText editPurchAmt;
    public String location;
    public int zip;
    public double localTax, totalTax, purchAmt, totalAmt;

       RadioGroup locationGroup = (RadioGroup) findViewById(R.id.radioGroup1);
       RadioGroup taxGroup = (RadioGroup) findViewById (R.id.radioGroup2);
       EditText editZip = (EditText) findViewById(R.id.zipEdit);
       EditText getPurchAmt = (EditText) findViewById(R.id.purchAmtEdit);

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

        locationGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checked) {

                if (checked == R.id.gpsRadio) {
                    editZip.setEnabled(false);
                } else if (checked == R.id.zipRadio) {
                    editZip.setEnabled(true);
                }
            }
        });

        taxGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checked) {

                if (checked == R.id.generalRadio) {
                    editPurchAmt.setText("100.00");
                } else if (checked == R.id.zipRadio) {
                    editPurchAmt.setText("10.00");
                }
            }
        });    
    }
    }

And finally, the debug log:

Target device: MyNexus [emulator-5554]
No apk changes detected since last installation, skipping installation of C:\Users\eliza\AndroidStudioProjects\Week3App\app\build\outputs\apk\app-debug.apk
Force stopping package: com.example.eliza.week3app
DEVICE SHELL COMMAND: am force-stop com.example.eliza.week3app
Launching application: com.example.eliza.week3app/com.example.eliza.week3app.Main.
DEVICE SHELL COMMAND: am start -D -n "com.example.eliza.week3app/com.example.eliza.week3app.Main" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
Client not ready yet.
WARNING: linker: libdvm. so has text relocations. This is wasting memory and is a security risk. Please fix.
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.example.eliza.week3app/.Main }
Connected to the target VM, address: 'localhost:8617', transport: 'socket'
Disconnected from the target VM, address: 'localhost:8617', transport: 'socket'

I'm really stumped as to what's going on here.

Answer 1

You have a block of code that's trying to grab view references during the activity object instantion:

RadioGroup locationGroup = (RadioGroup) findViewById(R.id.radioGroup1);
RadioGroup taxGroup = (RadioGroup) findViewById (R.id.radioGroup2);
EditText editZip = (EditText) findViewById(R.id.zipEdit);
EditText getPurchAmt = (EditText) findViewById(R.id.purchAmtEdit);

Instead you need to do all this only after setContentView is finished. There are no views to find before then.

Answer 2

You are not instantiating editPurchAmt yet and trying to set text to editPurchAmt which is null right now . please give reference to editPurchAmt from your view before use it.

Answer 3

please move the following:

RadioGroup locationGroup = (RadioGroup) findViewById(R.id.radioGroup1);
  RadioGroup taxGroup = (RadioGroup) findViewById (R.id.radioGroup2);
  EditText editZip = (EditText) findViewById(R.id.zipEdit);
  EditText getPurchAmt = (EditText) findViewById(R.id.purchAmtEdit);

inside the onCreate method

Answer 4

Replace your code of onCreate() to following,

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

        RadioGroup locationGroup = (RadioGroup) findViewById(R.id.radioGroup1);
        RadioGroup taxGroup = (RadioGroup) findViewById (R.id.radioGroup2);
        EditText editZip = (EditText) findViewById(R.id.zipEdit);
        EditText getPurchAmt = (EditText) findViewById(R.id.purchAmtEdit);

        locationGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checked) {

                if (checked == R.id.gpsRadio) {
                    editZip.setEnabled(false);
                } else if (checked == R.id.zipRadio) {
                    editZip.setEnabled(true);
                }
            }
        });

        taxGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checked) {

                if (checked == R.id.generalRadio) {
                    editPurchAmt.setText("100.00");
                } else if (checked == R.id.zipRadio) {
                    editPurchAmt.setText("10.00");
                }
            }
        });
    }