我创建了我的MainActivity应该午餐的新活动，以及应用程序在新活动开始时崩溃的原因（称为GamePlayActivity）。 这是java代码：
Intent startGameDrill = new Intent(MainActivity.this, GamePlayActivity.class);
startActivity(startGameDrill);
这是startGameDrill：
package com.simplemathgame;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
public class GamePlayActivity extends MainActivity {
int addDrills;
int subDrils;
int mulDrills;
int divDrills;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game_play);
try {
numberOfAddDrills = (TextView) findViewById(R.id.add_drills_number);
numberOfSubDrills = (TextView) findViewById(R.id.sub_drills_number);
numberOfMulDrills = (TextView) findViewById(R.id.mul_drills_number);
numberOfDivDrills = (TextView) findViewById(R.id.div_drills_number);
minBoundText = (TextView) findViewById(R.id.min_text);
maxBoundText = (TextView) findViewById(R.id.max_text);
} catch (Exception e1) {
// TODO Auto-generated catch block
Log.w("game","error");
}
try {
addDrills = Integer.parseInt((String) numberOfAddDrills.getText());
subDrils = Integer.parseInt((String) numberOfSubDrills.getText());
mulDrills = Integer.parseInt((String) numberOfMulDrills.getText());
divDrills = Integer.parseInt((String) numberOfDivDrills.getText());
} catch (NumberFormatException e) {
Log.w("GameDrills","string to int");
}
Log.w("add", "" + addDrills);
Log.w("add", "" + subDrils);
Log.w("add", "" + mulDrills);
Log.w("add", "" + divDrills);
}
}
这是清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.simplemathgame"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:theme="@style/AppTheme" >
<activity
android:name="com.simplemathgame.Splash"
android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.simplemathgame.MainActivity"
android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
<intent-filter>
<action android:name="com.simplemathgame.MainActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.simplemathgame.GamePlayActivity"
android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
</activity>
</application>
</manifest>
这是logCat：
12-21 22:05:53.949: D/dalvikvm(610): GC_EXTERNAL_ALLOC freed 42K, 53% free 2546K/5379K, external 1917K/2137K, paused 41ms
12-21 22:06:32.809: D/AndroidRuntime(610): Shutting down VM
12-21 22:06:32.809: W/dalvikvm(610): threadid=1: thread exiting with uncaught exception (group=0x40015560)
12-21 22:06:32.818: E/AndroidRuntime(610): FATAL EXCEPTION: main
12-21 22:06:32.818: E/AndroidRuntime(610): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.simplemathgame/com.simplemathgame.GamePlayActivity}: java.lang.NullPointerException
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.os.Handler.dispatchMessage(Handler.java:99)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.os.Looper.loop(Looper.java:123)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread.main(ActivityThread.java:3683)
12-21 22:06:32.818: E/AndroidRuntime(610): at java.lang.reflect.Method.invokeNative(Native Method)
12-21 22:06:32.818: E/AndroidRuntime(610): at java.lang.reflect.Method.invoke(Method.java:507)
12-21 22:06:32.818: E/AndroidRuntime(610): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-21 22:06:32.818: E/AndroidRuntime(610): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-21 22:06:32.818: E/AndroidRuntime(610): at dalvik.system.NativeStart.main(Native Method)
12-21 22:06:32.818: E/AndroidRuntime(610): Caused by: java.lang.NullPointerException
12-21 22:06:32.818: E/AndroidRuntime(610): at com.simplemathgame.GamePlayActivity.onCreate(GamePlayActivity.java:31)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-21 22:06:32.818: E/AndroidRuntime(610): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
12-21 22:06:32.818: E/AndroidRuntime(610): ... 11 more
以下是GamePlayActivity的布局：
<?xml version="1.0" encoding="utf-8"?>
<TableLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:background="#000044">
<TableRow
android:layout_marginTop="10dp"
android:gravity="center_vertical" >
<TextView
android:textColor="#FFFFFFFF"
android:textSize="16sp"
android:textStyle="bold"
android:text="Addition Drills:"/>
</TableRow>
</TableLayout>
为什么会崩溃？
答案 0 :(得分：4)
看看这里：
12-21 22:06:32.818: E/AndroidRuntime(610): Caused by: java.lang.NullPointerException
12-21 22:06:32.818: E/AndroidRuntime(610): at com.simplemathgame.GamePlayActivity.onCreate(GamePlayActivity.java:31)
GamePlayActivity.java的第31行是这一行：
addDrills = Integer.parseInt((String) numberOfAddDrills.getText());
由于此行中唯一引用成员或方法的是numberOfAddDrills，因此它必须为空。
在使用findViewById时，请考虑检查例外情况;但是，如果找不到视图，它将只返回null，而不是抛出异常。
查看您发布的activity_game_play.xml;没有TextView与android:id="@+id/add_drills_number"。您需要创建它，并为其他五个TextView创建相同的交易。
哦，还有一个提示：如果您无意阅读日志，请不要仅使用} catch (Exception e1) {，尤其是来捕获常规异常。我不能告诉你人们多少次错过了这样的错误。
如果你想从另一个布局传递值，你有两个选择：保持对View个对象的引用（这有点傻，不要这样做）;或者将您需要的数据传递给新的Activity：
startGameDrill.putExtra("myIntExtra", 5); // For example
然后，在GamePlayActivity.onCreate()中，您可以使用getIntent()的附加功能获取它：
Bundle extras = getIntent().getExtras();
int myIntExtra = extras.getInt("myIntExtra");
然后使用那个值，而不是依赖于前一个布局中的视图。有一个更全面的例子in this answer。
答案 1 :(得分：0)
按照堆栈跟踪，直到找到对您的类的一些引用：
它显示：
12-21 22:06:32.818: E/AndroidRuntime(610): Caused by: java.lang.NullPointerException
12-21 22:06:32.818: E/AndroidRuntime(610): at com.simplemathgame.GamePlayActivity.onCreate(GamePlayActivity.java:31)
所以你在GamePlayActivity.java的第31行创建了一个NullPointerException
第31行：
addDrills = Integer.parseInt((String) numberOfAddDrills.getText());
所以也许numberOfAddDrills为空？