android program crashing (new to platform)

问题

So it is my first real Android program (!hello world), but i do have java experience.The program compiles fine, but on running it crashes as soon as it opens (tried debugging, but it crashes before it hits my breakpoint). Was looking for any advice from anyone who is more experienced with android.

package org.me.tipcalculator;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.text.NumberFormat;
import android.util.Log;

public class TipCalculator extends Activity {

public static final String tag = "TipCalculator";

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.main);

    final EditText mealpricefield = (EditText) findViewById(R.id.mealprice);
    final TextView answerfield = (TextView) findViewById(R.id.answer);

    final Button button =  (Button) findViewById(R.id.calculate);
    button.setOnClickListener(new Button.OnClickListener()
    {
        public void onClick(View v) {
            try
            {
                Log.i(tag, "onClick invoked.");
                String mealprice = mealpricefield.getText().toString();

                Log.i(tag, "mealprice is [" + mealprice + "]");
                String answer = "";

                if (mealprice.indexOf("$") == -1)
                {
                    mealprice = "$" + mealprice;
                }

                float fmp = 0.0F;

                NumberFormat nf =
                        java.text.NumberFormat.getCurrencyInstance();

                fmp = nf.parse(mealprice).floatValue();

                fmp *= 1.2;

                Log.i(tag, "Total Meal Price (unformatted) is [" + fmp + "]");

                answer = "Full Price, including 20% Tip: " + nf.format(fmp);

                answerfield.setText(answer);

                Log.i(tag, "onClick Complete");

            }
            catch(java.text.ParseException pe){
                Log.i (tag ,"Parse exception caught");
                answerfield.setText("Failed to parse amount?");
            }
            catch(Exception e){
                Log.e (tag ,"Failed to Calculate Tip:" + e.getMessage());
                e.printStackTrace();
                answerfield.setText(e.getMessage());
            }
        }
    }
    );
}

Just in case it helps heres the xml

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Android Tip Calculator"/>
<EditText
    android:id="@+id/mealprice"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:autoText="true"/>
<Button
    android:id="@+id/calculate"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Calculate Tip"/>
<TextView
    android:id= "@+id/answer"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text=""/>
</LinearLayout>

回答1:

You may forget to register your activity name in the AndroidManifest.xml. It is a very common mistake for starters. AndroidManifest.xml should be like this:

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

回答2:

Use adb logcat, DDMS, or the DDMS perspective in Eclipse to find the Java stack trace that caused your crash.

来源：https://stackoverflow.com/questions/1352950/android-program-crashing-new-to-platform

标签

android

calculator