-1

このウェブページからこのコードを実装しようとしています。

しかし、何らかの理由で私は取得していNullPointerExceptionます:

    08-05 08:59:09.512: E/AndroidRuntime(875): java.lang.NullPointerException
    08-05 08:59:09.512: E/AndroidRuntime(875):  at com.example.basiccountdown.MainActivity$1.onTick(MainActivity.java:23)

コード：

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_timer);
    startB = (Button) this.findViewById(R.id.button);
    startB.setOnClickListener(this);

    text = (TextView) this.findViewById(R.id.timer);
    countDownTimer = new MyCountDownTimer(startTime, interval);

    text.setText(text.getText() + String.valueOf(startTime/1000));

    }

より多くのスタックトレース

08-05 09:21:44.313: D/AndroidRuntime(1258): Shutting down VM
08-05 09:21:44.313: W/dalvikvm(1258): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
08-05 09:21:44.412: E/AndroidRuntime(1258): FATAL EXCEPTION: main
08-05 09:21:44.412: E/AndroidRuntime(1258): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.basiccountdown/com.example.basiccountdown.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.basiccountdown.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.basiccountdown-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.basiccountdown-2, /system/lib]]
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.os.Looper.loop(Looper.java:137)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread.main(ActivityThread.java:5103)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at java.lang.reflect.Method.invokeNative(Native Method)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at java.lang.reflect.Method.invoke(Method.java:525)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at dalvik.system.NativeStart.main(Native Method)
08-05 09:21:44.412: E/AndroidRuntime(1258): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.basiccountdown.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.basiccountdown-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.basiccountdown-2, /system/lib]]
08-05 09:21:44.412: E/AndroidRuntime(1258):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:53)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
08-05 09:21:44.412: E/AndroidRuntime(1258):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
08-05 09:21:44.412: E/AndroidRuntime(1258):     ... 11 more
08-05 09:28:51.782: D/AndroidRuntime(1307): Shutting down VM
08-05 09:28:51.782: W/dalvikvm(1307): threadid=1: thread exiting with uncaught exception (group=0x414c4700)

23行目はsuper.onCreate(savedInstanceState);

4

3 に答える 3

1

Add your MainActivity to the AndroidManifest. This should fix the problem. It is the tutorial, which didn't say anywhere that this activity should be added there. It is for new projects, where this happens automatically. Add this into the manifest:

<activity android:name="com.example.basiccountdown.MainActivity">

Then go to Project -> Properties -> Builders too.

于 2013-08-05T14:18:07.923 に答える
1

タイマー アクティビティ クラスの名前を MainActivity に変更します。

于 2013-08-05T13:58:24.233 に答える
0

あなたが言及したコードをコピーした場合、私が提案できる2つのことがあります：

1) メイン アクティビティを適切に定義しているかどうかをマニフェストで確認します。

2) /res/layout/activity_timer.xml で、ID「timer」のテキスト ビューがあることを確認します。

于 2013-08-05T14:25:35.610 に答える