Question

Android新手。

我尝试在我的onClickListener中创建一个简单的意图，它将打开一个新页面。但是，当我单击按钮时，应用程序崩溃了。我不确定是什么问题。

这是我的倾听者

 buttonCheat.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
           Intent cheatView = new Intent(getApplicationContext(),CheatActivity.class);
            startActivity(cheatView);
        }

这里我在我的清单文件中声明了活动

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
      android:name=".QuizActivity"
      android:label="@string/app_name" >
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
    <activity
      android:name=".CheatActivity"
      android:label="@string/app_name" />
  </application>

以下是相关日志

10-03 01:51:23.770    2630-2630/? D/CheatActivity﹕ onCreate() called
10-03 01:51:23.777    2630-2630/? D/AndroidRuntime﹕ Shutting down VM
10-03 01:51:23.777    2630-2630/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: itp341.exercises.week6.geoquiz, PID: 2630
    java.lang.RuntimeException: Unable to start activity ComponentInfo{itp341.exercises.week6.geoquiz/itp341.exercises.week6.geoquiz.CheatActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.ComponentName.toString()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.ComponentName.toString()' on a null object reference
            at itp341.exercises.week6.geoquiz.CheatActivity.onCreate(CheatActivity.java:49)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

来自CheatActivity

public class CheatActivity extends Activity {

    private static final String TAG = "CheatActivity";


    // View references
    TextView textAnswer;
    Button buttonShowAnswer;

    // instance variables
    boolean answerIsTrue;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate() called");
        setContentView(R.layout.activity_cheat);
        Log.d(TAG, getCallingActivity().toString());
=
        //find views
        textAnswer = (TextView) findViewById(R.id.text_answer);
        buttonShowAnswer = (Button) findViewById(R.id.button_show_answer);
    }


}

Answer 1

 Intent cheatView = new Intent(getApplicationContext(),CheatActivity.class);

这就是存在异常的原因，尝试使用它来替换它，

Intent cheatView = new Intent(QuizActivity.this,CheatActivity.class);

因为应用程序上下文无法启动活动。

简单的意图崩溃应用程序

1 个答案: