当我开始主要活动时,我得到以下错误堆栈:
12-10 01:46:41.257: E/AndroidRuntime(849): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.projetofinal_pesquisa_de_campo/br.domBosco.projetofinal_pesquisa_de_campo.MainActivity}: java.lang.NullPointerException
12-10 01:46:41.257: E/AndroidRuntime(849): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.os.Handler.dispatchMessage(Handler.java:99)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.os.Looper.loop(Looper.java:123)
12-10 01:46:41.257: E/AndroidRuntime(849): at android.app.ActivityThread.main(ActivityThread.java:3683)
12-10 01:46:41.257: E/AndroidRuntime(849): at java.lang.reflect.Method.invokeNative(Native Method)
12-10 01:46:41.257: E/AndroidRuntime(849): at java.lang.reflect.Method.invoke(Method.java:507)
12-10 01:46:41.257: E/AndroidRuntime(849): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-10 01:46:41.257: E/AndroidRuntime(849): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-10 01:46:41.257: E/AndroidRuntime(849): at dalvik.system.NativeStart.main(Native Method)
12-10 01:46:41.257: E/AndroidRuntime(849): Caused by: java.lang.NullPointerException
12-10 01:46:41.257: E/AndroidRuntime(849): at br.domBosco.projetofinal_pesquisa_de_campo.MainActivity.onCreate(MainActivity.java:46)
我无法弄清楚为什么会发生这种情况,搜索时间会尝试解决此问题。
这是我的主要活动:
public class MainActivity extends Activity {
LinearLayout container;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// LeitorXml lxml = new LeitorXml();
// try {
// Questionario questionario = lxml.getQuestionariosFromXml2(this);
// } catch (XmlPullParserException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
container = (LinearLayout) findViewById(R.id.svQuestionario);
LayoutInflater layoutInflater =
(LayoutInflater) getBaseContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final View viewDinamica = layoutInflater.inflate(R.layout.campos_dinamicos, null);
//setContentView(R.layout.campos_dinamicos);
TextView lblPergunta = (TextView)viewDinamica.findViewById(R.id.lblCampoDinamico);
lblPergunta.setText("Uma Pergunta apenas");
EditText txtPergunta = (EditText)viewDinamica.findViewById(R.id.txtCampoDinamico);
container.addView(viewDinamica);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
以下是我的xml布局配置文件:
activity_main.xml中:
<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="@+id/lblNomeQuestionario"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<ScrollView
android:id="@+id/svQuestionario"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/lblNomeQuestionario"
android:layout_below="@id/lblNomeQuestionario"
android:layout_marginTop="18dp" >
<LinearLayout
android:id="@+id/container"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</ScrollView>
</RelativeLayout>
这里是我的campos_dinamicos.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/lblCampoDinamico"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/txtCampoDinamico"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@id/lblCampoDinamico"
android:ems="10" />
</RelativeLayout>
我试着这样做: http://android-er.blogspot.com.br/2013/05/add-and-remove-view-dynamically.html
有人可以帮我吗?我非常noob编程到android,所以也许这是一个非常简单的错误!谢谢!
答案 0 :(得分:3)
<ScrollView
android:id="@+id/svQuestionario"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/lblNomeQuestionario"
android:layout_below="@id/lblNomeQuestionario"
android:layout_marginTop="18dp" >
<LinearLayout
android:id="@+id/container"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
您将R.id.svQuestionario
投射为LinearLayout
。这将导致ClassCastException
。
此外,您无法将另一个孩子添加到ScrollView
。因此,要解决此问题,请使用
container = (LinearLayout) findViewById(R.id.container);