我正在尝试在eclipse中创建一个简单的android应用程序。当我试图运行由eclipse自动创建的“Hello world”时，模拟器工作正常，并且工作正常。但是当我尝试创建一个简单的程序并运行它时，模拟器弹出“不幸的是OddOrEven已停止”。我也试过我的Android手机，但他们有同样的错误。我该怎么办？我只是一个初学者，试图学习如何制作Android应用程序。
这是我的Android清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.IDB.oddoreven"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.IDB.oddoreven.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是我的主要活动文件：
package com.IDB.oddoreven;
import android.support.v7.app.ActionBarActivity;
//import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.*;
//import android.os.Build;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText input = (EditText) findViewById(R.id.tbInput);
final TextView output = (TextView) findViewById(R.id.tbResult);
Button check = (Button) findViewById(R.id.btnCheck);
check.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Double num = Double.parseDouble(input.getText().toString());
num = Double.parseDouble(calc.multiNum(num));
output.setText(num+"");
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
}
}
这是我的calc.java文件：
package com.IDB.oddoreven;
public class calc {
public static String multiNum(double x){
String re= "";
double num = x * 5;
re = num + "";
return re;
}
}
*这是我的fragment_main.xml：*
<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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.IDB.oddoreven.MainActivity$PlaceholderFragment" >
<EditText
android:id="@+id/tbInput"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:inputType="numberDecimal"
android:textSize="12sp" >
<requestFocus />
</EditText>
<Button
android:id="@+id/btnCheck"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/tbInput"
android:layout_centerVertical="true"
android:text="@string/button" />
<EditText
android:id="@+id/tbResult"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/btnCheck"
android:layout_alignParentRight="true"
android:layout_below="@+id/btnCheck"
android:inputType="text" />
</RelativeLayout>
这是我的 logcat ：
03-23 13:29:24.383: D/AndroidRuntime(601): Shutting down VM
03-23 13:29:24.393: W/dalvikvm(601): threadid=1: thread exiting with uncaught exception (group=0xb3aa6d58)
03-23 13:29:24.433: E/AndroidRuntime(601): FATAL EXCEPTION: main
03-23 13:29:24.433: E/AndroidRuntime(601): Process: com.IDB.oddoreven, PID: 601
03-23 13:29:24.433: E/AndroidRuntime(601): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.IDB.oddoreven/com.IDB.oddoreven.MainActivity}: java.lang.NullPointerException
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2208)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2270)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread.access$800(ActivityThread.java:138)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1209)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.os.Handler.dispatchMessage(Handler.java:102)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.os.Looper.loop(Looper.java:136)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread.main(ActivityThread.java:5042)
03-23 13:29:24.433: E/AndroidRuntime(601): at java.lang.reflect.Method.invokeNative(Native Method)
03-23 13:29:24.433: E/AndroidRuntime(601): at java.lang.reflect.Method.invoke(Method.java:515)
03-23 13:29:24.433: E/AndroidRuntime(601): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:776)
03-23 13:29:24.433: E/AndroidRuntime(601): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
03-23 13:29:24.433: E/And`enter code here`roidRuntime(601): at dalvik.system.NativeStart.main(Native Method)
03-23 13:29:24.433: E/AndroidRuntime(601): Caused by: java.lang.NullPointerException
03-23 13:29:24.433: E/AndroidRuntime(601): at com.IDB.oddoreven.MainActivity.onCreate(MainActivity.java:27)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.Activity.performCreate(Activity.java:5231)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-23 13:29:24.433: E/AndroidRuntime(601): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2172)
03-23 13:29:24.433: E/AndroidRuntime(601): ... 11 more
答案 0 :(得分：0)
也许我看到了问题。您的观看次数在fragment_main和Activity充气activity_main，而您的片段PlaceholderFragment会在按钮和EditTexts所在的位置膨胀。
你应该将它放在片段onCreateView方法中：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
// don't forget, you need the inflated View to find their ids (rootView).
final EditText input = (EditText) rootView.findViewById(R.id.tbInput);
final EditText output = (EditText) rootView.findViewById(R.id.tbResult);
Button check = (Button) rootView.findViewById(R.id.btnCheck);
check.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Double num = Double.parseDouble(input.getText().toString());
num = Double.parseDouble(calc.multiNum(num));
output.setText(num+"");
}
});
return rootView;
}
如果有帮助，请告诉我。