我正在尝试在 android 应用程序中以编程方式添加 SeekBar。
这是我的代码：
SeekBar seekbar = new SeekBar(this);
seekbar.setMax(6);
seekbar.setLayoutParams(new LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.WRAP_CONTENT));
LinearLayout linearLayout = (LinearLayout) findViewById(R.id.linearLayout1);
linearLayout.addView(seekBar);
但是，当调用 addView 方法时，我得到了这个异常
06-21 22:11:26.286: E/AndroidRuntime(13354): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.T4J_OAuth.activities/com.T4J_OAuth.activities.ExampleTabActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.T4J_OAuth.activities/com.T4J_OAuth.activities.feedbackActivity}: java.lang.NullPointerException
我是不是对代码做错了什么。请注意，我尝试添加 seekBar 的活动是包含选项卡的父活动的一部分。因此，此活动是选项卡之一。
这是我的反馈活动类
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.feedback_form)
String unitName = "Unit:" + ExampleTabActivity.unitName;
final TextView textViewToChange = (TextView) findViewById(R.id.textView1);
textViewToChange.setText(unitName);
String lectureName = "Lecture:" + ExampleTabActivity.lectureName;
final TextView textViewToChange2 = (TextView) findViewById(R.id.textView2);
textViewToChange2.setText(lectureName);
Spinner spinner = (Spinner) findViewById(R.id.spinner1);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, ExampleTabActivity.subsections);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
SeekBar seekbar = new SeekBar(this);
seekbar.setMax(6);
seekbar.setLayoutParams(new LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.WRAP_CONTENT));*/
LinearLayout linearLayout = (LinearLayout) findViewById(R.id.linearLayout1);
linearLayout.addView(seekBar);
}
创建选项卡的 TabActivity 的这一部分
TabHost tabHost = getTabHost();
TabHost.TabSpec spec;
Intent newIntent = new Intent().setClass(this, feedbackActivity.class);
spec = tabHost
.newTabSpec("structured")
.setIndicator(createTabView(this, "Structured"))
.setContent(newIntent);
tabHost.addTab(spec);
Intent newIntent2 = new Intent().setClass(this, feedbackNLActivity.class);
spec = tabHost
.newTabSpec("nl")
.setIndicator(createTabView(this, "Natural Language"))
.setContent(newIntent2);
tabHost.addTab(spec);
tabHost.setCurrentTab(0);
}
private static View createTabView(final Context context, final String text) {
View view = LayoutInflater.from(context).inflate(R.layout.tab, null);
TextView tv = (TextView) view.findViewById(R.id.tabText);
tv.setText(text);
return view;
}
这是错误的完整堆栈跟踪
06-21 22:21:11.427: E/AndroidRuntime(14643): FATAL EXCEPTION: main
06-21 22:21:11.427: E/AndroidRuntime(14643): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.T4J_OAuth.activities/com.T4J_OAuth.activities.ExampleTabActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.T4J_OAuth.activities/com.T4J_OAuth.activities.feedbackActivity}: java.lang.NullPointerException
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1830)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1851)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.access$1500(ActivityThread.java:132)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.os.Handler.dispatchMessage(Handler.java:99)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.os.Looper.loop(Looper.java:150)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.main(ActivityThread.java:4293)
06-21 22:21:11.427: E/AndroidRuntime(14643): at java.lang.reflect.Method.invokeNative(Native Method)
06-21 22:21:11.427: E/AndroidRuntime(14643): at java.lang.reflect.Method.invoke(Method.java:507)
06-21 22:21:11.427: E/AndroidRuntime(14643): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
06-21 22:21:11.427: E/AndroidRuntime(14643): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
06-21 22:21:11.427: E/AndroidRuntime(14643): at dalvik.system.NativeStart.main(Native Method)
06-21 22:21:11.427: E/AndroidRuntime(14643): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.T4J_OAuth.activities/com.T4J_OAuth.activities.feedbackActivity}: java.lang.NullPointerException
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1830)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.startActivityNow(ActivityThread.java:1656)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:656)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.widget.TabHost.setCurrentTab(TabHost.java:326)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.widget.TabHost.addTab(TabHost.java:216)
06-21 22:21:11.427: E/AndroidRuntime(14643): at com.T4J_OAuth.activities.ExampleTabActivity.onCreate(ExampleTabActivity.java:354)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1794)
06-21 22:21:11.427: E/AndroidRuntime(14643): ... 11 more
06-21 22:21:11.427: E/AndroidRuntime(14643): Caused by: java.lang.NullPointerException
06-21 22:21:11.427: E/AndroidRuntime(14643): at com.T4J_OAuth.activities.feedbackActivity.onCreate(feedbackActivity.java:85)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
06-21 22:21:11.427: E/AndroidRuntime(14643): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1794)
06-21 22:21:11.427: E/AndroidRuntime(14643): ... 20 more
这是我的 xml 文件
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:overScrollMode="always"
android:isScrollContainer="true"
android:scrollbarAlwaysDrawVerticalTrack="true"
android:scrollbarStyle="outsideInset"
android:scrollbars="vertical">
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:paddingTop="5dp"
android:text="Unit Name: Data Structurs"
android:textSize="20dp" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:text="Lecture Name: Queues"
android:textSize="15dp" />
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
</LinearLayout>
</ScrollView>
提前致谢。