所以我不知道关于双重职位的规则是什么，任何我没有得到其他问题跟进支持的人..任何我提出问题的人，这就是我的logcat
05-28 19:45:03.464: I/ActivityManager(274): Start proc xela.kasea.flyffresell for activity xela.kasea.flyffresell/.Main: pid=793 uid=10046 gids={50046, 1028}
05-28 19:45:03.474: D/dalvikvm(793): Not late-enabling CheckJNI (already on)
05-28 19:45:04.154: I/ARMAssembler(36): generated scanline__00000077:03010104_00008001_00000000 [ 89 ipp] (110 ins) at [0x41548840:0x415489f8] in 564149 ns
05-28 19:45:04.294: D/dalvikvm(793): GC_FOR_ALLOC freed 81K, 6% free 2642K/2784K, paused 26ms, total 27ms
05-28 19:45:04.294: I/dalvikvm-heap(793): Grow heap (frag case) to 3.318MB for 714016-byte allocation
05-28 19:45:04.334: D/dalvikvm(793): GC_FOR_ALLOC freed 2K, 5% free 3337K/3484K, paused 34ms, total 34ms
05-28 19:45:04.414: I/Tag2(793): This is my error msg
05-28 19:45:04.414: D/AndroidRuntime(793): Shutting down VM
05-28 19:45:04.414: W/dalvikvm(793): threadid=1: thread exiting with uncaught exception (group=0x41465700)
05-28 19:45:04.425: E/AndroidRuntime(793): FATAL EXCEPTION: main
05-28 19:45:04.425: E/AndroidRuntime(793): java.lang.RuntimeException: Unable to start activity ComponentInfo{xela.kasea.flyffresell/xela.kasea.flyffresell.Main}: java.lang.NullPointerException
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.os.Handler.dispatchMessage(Handler.java:99)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.os.Looper.loop(Looper.java:137)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread.main(ActivityThread.java:5103)
05-28 19:45:04.425: E/AndroidRuntime(793): at java.lang.reflect.Method.invokeNative(Native Method)
05-28 19:45:04.425: E/AndroidRuntime(793): at java.lang.reflect.Method.invoke(Method.java:525)
05-28 19:45:04.425: E/AndroidRuntime(793): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
05-28 19:45:04.425: E/AndroidRuntime(793): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-28 19:45:04.425: E/AndroidRuntime(793): at dalvik.system.NativeStart.main(Native Method)
05-28 19:45:04.425: E/AndroidRuntime(793): Caused by: java.lang.NullPointerException
05-28 19:45:04.425: E/AndroidRuntime(793): at xela.kasea.flyffresell.Main.onCreate(Main.java:31)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.Activity.performCreate(Activity.java:5133)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-28 19:45:04.425: E/AndroidRuntime(793): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
05-28 19:45:04.425: E/AndroidRuntime(793): ... 11 more
05-28 19:45:04.433: W/ActivityManager(274): Force finishing activity xela.kasea.flyffresell/.Main
05-28 19:45:04.743: I/WindowManager(274): Screenshot max retries 4 of Token{41792b40 ActivityRecord{418a4ce0 u0 xela.kasea.flyffresell/.Main}} appWin=Window{41943b50 u0 Starting xela.kasea.flyffresell} drawState=4
05-28 19:45:04.743: W/WindowManager(274): Screenshot failure taking screenshot for (400x800) to layer 21010
05-28 19:45:05.133: D/AlertService(580): Beginning updateAlertNotification
05-28 19:45:05.214: D/AlertService(580): No fired or scheduled alerts
05-28 19:45:05.263: W/ActivityManager(274): Activity pause timeout for ActivityRecord{418a4ce0 u0 xela.kasea.flyffresell/.Main}
05-28 19:45:05.593: D/AlertService(580): Scheduling next alarm with AlarmScheduler. sEventReminderReceived: null
05-28 19:45:05.853: D/AlarmScheduler(580): No events found starting within 1 week.
05-28 19:45:06.503: I/Process(793): Sending signal. PID: 793 SIG: 9
05-28 19:45:06.513: I/ActivityManager(274): Process xela.kasea.flyffresell (pid 793) has died.
这是我的main.java。注意：我只使用一堂课。
package xela.kasea.flyffresell;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.ToggleButton;
public class Main extends Activity implements OnClickListener{
EditText perin, amountPrUnit, buy, sell;
ToggleButton lazy;
Button clear, submit, ret;
double ans, subAnswer;
TextView pEarned, tAmount;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.display);
Log.i("Tag2", "This is my error msg");
initalizer();
lazy.setOnClickListener(this);
clear.setOnClickListener(this);
submit.setOnClickListener(this);
ret.setOnClickListener(this);
/*String a = perin.getText().toString();
String b = amountPrUnit.getText().toString();
String c = buy.getText().toString();
String d = sell.getText().toString(); */
}
private void initalizer() {
// TODO Auto-generated method stub
perin = (EditText) findViewById(R.id.etHowRich);
amountPrUnit = (EditText) findViewById(R.id.etAmountPrUnit);
buy = (EditText) findViewById(R.id.etBuying);
sell = (EditText) findViewById(R.id.etSellingPrUnit);
lazy = (ToggleButton) findViewById(R.id.tbBuying);
clear = (Button) findViewById(R.id.bClear);
submit = (Button) findViewById(R.id.bSubmit);
ret = (Button) findViewById(R.id.bReturn);
pEarned = (TextView) findViewById(R.id.tvEarned);
tAmount = (TextView) findViewById(R.id.tvAmount);
/*int a = Integer.parseInt(perin.getText().toString());
int b = Integer.parseInt(amountPrUnit.getText().toString());
int c = Integer.parseInt(buy.getText().toString());
int d = Integer.parseInt(sell.getText().toString());*/
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
int a = Integer.parseInt(perin.getText().toString());
int b = Integer.parseInt(amountPrUnit.getText().toString());
int c = Integer.parseInt(buy.getText().toString());
int d = Integer.parseInt(sell.getText().toString());
switch(v.getId()){
case R.id.bClear:
perin.setText("");
amountPrUnit.setText("");
buy.setText("");
sell.setText("");
lazy.setChecked(false);
break;
case R.id.bReturn:
setContentView(R.layout.display);
break;
case R.id.bSubmit:
pEarned.setText(c*d-(a-(b*c)));
tAmount.setText(c*d+(a-(a-(b*c))));
setContentView(R.layout.finish);
break;
case R.id.tbBuying:
if (lazy.isChecked()){
buy.setText("");
double subAnswer = 0;
int ans = 0;
subAnswer = a/b;
ans = (int) Math.floor(subAnswer);
/*new Integer((int) ans).toString();
Integer.toString(answer);*/
buy.setText(ans);;
}
break;
}
}
}
该应用程序应该做的是，获取几个用户输入的数字，并对它们进行一些数学运算。
如果需要的话，这是清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="xela.kasea.flyffresell"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="16"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".Main"
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>
参考方案
我认为用户的此评论需要一个答案，该答案解释Java中null的基本主题：
如果我可能要问，什么是NullPointerException？
null指针表示您正在尝试操作没有分配任何内存的Object变量。 NullPointerException是Java告诉您的方式：“嘿，您要操作的变量（即，将侦听器设置为）指向没有内存位置；该变量没有实例化的Object或已经被实例化您正在尝试使用尚未建成的建筑物的浴室。”
stacktrace很不错（您应该和他成为朋友），并告诉我们Exception在代码的哪一行被抛出：
05-28 19:45:04.425: E/AndroidRuntime(793): Caused by: java.lang.NullPointerException
05-28 19:45:04.425: E/AndroidRuntime(793): at xela.kasea.flyffresell.Main.onCreate(Main.java:31)
这意味着您需要检查该行代码并找出哪个变量是null。大多数现代IDE都可以选择引入断点，以使您能够在运行时查看变量的状态。一旦知道哪个变量是null，就可以更轻松地找出原因。因此，根据您的情况，引起问题的行是Main.java的第31行。从评论中我们知道您说的是：
ret.setOnClickListender(this);
那给我们一个选择。 ret必须为null。然后我们问自己：
在正常情况下，可以使ret null发生什么？
1）变量未初始化；我们忘了初始化它。不是我们的情况。
2）对该变量进行了垃圾回收。不是我们的情况。
3）尝试初始化变量时出了点问题。可能是我们的情况。
在这种情况下，我们不会通过调用某个类的构造函数来初始化变量，而是通过方法（即findViewById()）来实现。此方法采用一个int，该id应该是我们要将View设置为的ret的null，并且它返回View或有问题的。因此，如果正确地认为这是错误的，则可能是我们使用了错误的ID。
因为实际上没有足够的信息来解决问题，所以此答案更多是显示思维模式而不是实际解决方案。
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