[英]NullPointerException on TextView using setText()
我是android編程的新手,並且遇到了我的老朋友NullPointerException
...
我已經花了很長時間了,但無法弄清楚出什么問題了。
當我嘗試調用任何.setText()
方法時,基本上給了我NullPointerException
,也許有人看到我在這里做錯了...(盡管我嘗試盡可能地遵循示例)
public class lessonView extends Activity {
TextView adressOfLecture;
TextView lecturer;
TextView lesson;
Lecture lecture;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_lesson_view);
Bundle data = getIntent().getExtras();
lecture = (Lecture) data.getParcelable("student");
adressOfLecture = (TextView)findViewById(R.id.lectureViewAdressLabel);
lecturer = (TextView)findViewById(R.id.lectureViewLecturerLabel);
lesson = (TextView)findViewById(R.id.lectureViewTitle);
updateLabels();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_lesson_view, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void updateLabels(){
adressOfLecture.setText(lecture.getRoom());
lecturer.setText(lecture.getTutor());
lesson.setText(lecture.getName());
}
}
另外,這是我的xml文件:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.coronarip7.app.stupla.lessonView">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="(ort)"
android:id="@+id/lectureViewAdressLabel"
android:layout_centerVertical="true"
android:layout_toStartOf="@+id/lectureViewTitle"
android:layout_marginRight="86dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="dozent"
android:id="@+id/lectureViewLecturerLabel"
android:layout_toEndOf="@+id/lectureViewTitle"
android:layout_alignTop="@+id/lectureViewAdressLabel"
android:layout_alignParentEnd="true"
android:layout_marginRight="27dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/lectureViewTitle"
android:gravity="center_horizontal"
android:text="test"
android:textSize="40dp"
android:textStyle="bold"
android:padding="10dp"
android:layout_row="0"
android:layout_column="0"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
和我得到的日志貓:
04-25 01:23:51.058 12236-12236/com.coronarip7.app.stupla E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.coronarip7.app.stupla, PID: 12236
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.coronarip7.app.stupla/com.coronarip7.app.stupla.lessonView}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
at android.app.ActivityThread.access$800(ActivityThread.java:145)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5081)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.coronarip7.app.stupla.lessonView.updateLabels(lessonView.java:59)
at com.coronarip7.app.stupla.lessonView.onCreate(lessonView.java:31)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
at android.app.ActivityThread.access$800(ActivityThread.java:145)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5081)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
認真的說,我對如何解決它沒有想法...
首先檢查您是否正確放置了多余的內容。 然后,我將在您的onCreate方法中使用以下測試:
Intent intent = getIntent();
if (intent.hasExtra("student")){
lecture = (Lecture) intent.getParcelableExtra("student");
}
然后測試演講是否為空,如Rami先前所寫。
好的,謝謝您的建議,但我會走全球路線。 我將創建一個數組的靜態版本(我想通過該數組通過Intent傳遞對象),然后將帶有coordiantes的int []數組傳遞給新視圖。
但是還是感謝您的快速解答!
(我是stackoverflow的新手,有沒有辦法將問題標記為“已解決”或“不再需要解決”?)
不要在代碼中使用靜態對象,例如數組,對象,它們在全局范圍內可用,您應該創建意圖並將數據添加到意圖中,然后調用活動
Intent intent = new Intent ();
intent.putExtra ("student",value);
以意圖開始活動,並在您的LessonViewActivity中檢查意圖
Intent intent = getIntent();
if (intent.hasExtra("student")){
lecture = (Lecture) intent.getParcelableExtra("student");
if (lecture !=null){
updateLabels ();
}
}
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