每当我想从我的班级运行 Intent 时，NPE [重复]

Question

我是 Android 应用开发的初学者。我已经完成了一些 Udemy 课程，但后来我意识到 Android Docs 实际上可能更适合为应用程序开发打下良好的基础。我现在正在尝试构建自己的应用程序，但遇到了这个问题。

我的班级

public class deleteInfluencer extends AppCompatActivity {

private Repository instanceOfRepository;

public static final int EDIT_BLOGGER_ACTIVITY_REQUEST_CODE = 1;

deleteInfluencer(Application application) {
    super();
    instanceOfRepository = new Repository(application);
}

void callDeleteInfluencer(int id) {
    instanceOfRepository.deleteInfluencerCalledFromRepository(id);
}

void callUpdateInfluencer() {
    Intent intent = new Intent(this, EditBloggerActivity.class);
    startActivityForResult(intent, EDIT_BLOGGER_ACTIVITY_REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == EDIT_BLOGGER_ACTIVITY_REQUEST_CODE && resultCode == RESULT_OK) {
        int id = 0;
        Tables tables = new Tables(
                id, // Blogger ID
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_NAME),
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_ADDRESS),
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_MOBILE_NUMBER),
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_FB),
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_IG),
                data.getStringExtra(EditBloggerActivity.EXTRA_EDIT_REPLY_EMAIL));
        instanceOfRepository.updateInfluencerCalledFromRepository(tables);
    } else {
        Toast.makeText(this, "Save Failed! fill out all fields", Toast.LENGTH_LONG).show();

    }
}
}

LOGCAT

2020-02-28 16:10:06.071 4258-4258/com.kurtsample.digitalcirclesprototype E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.kurtsample.digitalcirclesprototype, PID: 4258
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.content.ContextWrapper.getPackageName(ContextWrapper.java:142)
    at android.content.ComponentName.<init>(ComponentName.java:130)
    at android.content.Intent.<init>(Intent.java:6082)
    at com.kurtsample.digitalcirclesprototype.deleteInfluencer.callUpdateInfluencer(deleteInfluencer.java:31)
    at com.kurtsample.digitalcirclesprototype.Adapter$2.onClick(Adapter.java:95)
    at android.view.View.performClick(View.java:6597)
    at android.view.View.performClickInternal(View.java:6574)
    at android.view.View.access$3100(View.java:778)
    at android.view.View$PerformClick.run(View.java:25885)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

将Intent intent = new Intent(this, EditBloggerActivity.class); 中的this 替换为deleteInfluencer.this。所以你会有Intent intent = new Intent(deleteInfluencer.this, EditBloggerActivity.class);

另外，还有几点需要注意：

1. 活动类不应有构造函数。如果你想要什么 要充当构造函数，您可以使用生命周期方法。
2. 您的类名应以大写字母开头，并带有 单词“活动”，因此deleteInfluencer 应该 是DeleteInfluencerActivity