问题
I am a Beginner. I have a problem with a spinner. I want to create a spinner by using onItemSelected method and to display that selected spinner item in TextView
But my program is not running in emulator. it says "Program stopped".. what was my mistake in below program. Pls help me.. Thanks U..
My SpinOnItemActivity.java
package spinner.onitemsel;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.view.View.OnClickListener;
public class SpinOnItemActivity extends Activity
{
Spinner sp= (Spinner) findViewById(R.id.spin);;
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.spinner_array , android.R.layout.simple_spinner_item);
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_spin_on_item );
sp.performClick();
}
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setAdapter(adapter);
String Name = (String) sp.getSelectedItem();
TextView tview1 = (TextView)findViewById(R.id.testtxt );
tview1.setText(Name);
}
}
My activity_spin_on_item.xml file
<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"
tools:context=".SpinActivity" >
<Spinner
android:id="@+id/spin"
android:layout_width="149dp"
android:layout_height="66dp"
android:layout_alignBottom="@+id/button1"
android:layout_alignParentLeft="true"
android:layout_alignRight="@+id/testtxt"
android:layout_gravity="top" />
<TextView
android:id="@+id/testtxt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/testtxt2"
android:layout_centerHorizontal="true"
android:layout_marginBottom="44dp"
android:gravity="bottom"
android:text="Spin Txt" />
</RelativeLayout>
My logcat Report
12-10 09:58:40.988: W/Trace(837): Unexpected value from nativeGetEnabledTags: 0
12-10 09:58:41.168: W/Trace(837): Unexpected value from nativeGetEnabledTags: 0
12-10 09:58:41.198: W/Trace(837): Unexpected value from nativeGetEnabledTags: 0
12-10 09:58:41.878: D/dalvikvm(837): GC_CONCURRENT freed 51K, 6% free 2830K/2996K, paused 12ms+3ms, total 56ms
12-10 09:58:41.878: D/dalvikvm(837): WAIT_FOR_CONCURRENT_GC blocked 25ms
12-10 09:58:41.968: D/AndroidRuntime(837): Shutting down VM
12-10 09:58:41.968: W/dalvikvm(837): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
12-10 09:58:41.988: E/AndroidRuntime(837): FATAL EXCEPTION: main
12-10 09:58:41.988: E/AndroidRuntime(837): java.lang.RuntimeException: Unable to start activity ComponentInfo{spinner.onitemsel/spinner.onitemsel.SpinOnItemActivity}: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.os.Handler.dispatchMessage(Handler.java:99)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.os.Looper.loop(Looper.java:137)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread.main(ActivityThread.java:5039)
12-10 09:58:41.988: E/AndroidRuntime(837): at java.lang.reflect.Method.invokeNative(Native Method)
12-10 09:58:41.988: E/AndroidRuntime(837): at java.lang.reflect.Method.invoke(Method.java:511)
12-10 09:58:41.988: E/AndroidRuntime(837): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-10 09:58:41.988: E/AndroidRuntime(837): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-10 09:58:41.988: E/AndroidRuntime(837): at dalvik.system.NativeStart.main(Native Method)
12-10 09:58:41.988: E/AndroidRuntime(837): Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
12-10 09:58:41.988: E/AndroidRuntime(837): at android.view.ViewRootImpl.setView(ViewRootImpl.java:567)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:246)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.widget.PopupWindow.invokePopup(PopupWindow.java:993)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:899)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.widget.ListPopupWindow.show(ListPopupWindow.java:603)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.widget.Spinner$DropdownPopup.show(Spinner.java:981)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.widget.Spinner.performClick(Spinner.java:609)
12-10 09:58:41.988: E/AndroidRuntime(837): at spinner.onitemsel.SpinOnItemActivity.onCreate(SpinOnItemActivity.java:35)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.Activity.performCreate(Activity.java:5104)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-10 09:58:41.988: E/AndroidRuntime(837): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-10 09:58:41.988: E/AndroidRuntime(837): ... 11 more
12-10 10:03:42.109: I/Process(837): Sending signal. PID: 837 SIG: 9
My Edited Code: Pls Check it out..
package spinner.onitemsel;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
public class SpinOnItemActivity extends Activity
{
ArrayAdapter<CharSequence> adapter;
Spinner sp;
TextView tview1;
int length;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_spin_on_item );
sp= (Spinner) findViewById(R.id.spin);
adapter = ArrayAdapter.createFromResource(this, R.array.spinner_array , android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setAdapter(adapter);
sp.performClick();
}
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
String Name = (String) sp.getSelectedItem();
tview1 = (TextView)findViewById(R.id.testtxt );
tview1.setText(Name);
}
}
回答1:
Actually your Spinner sp is null, So when code line sp.performClick(); is executed in onCreate() the application crashes with Null Pointer Exception.
Because you are defining Spinner sp in above onCreate() so android doesn't find the Spinner sp from Layout Xml file. It should be after setContentView() so android nut shell has a reference of that Spinner for particular Activity.
Solution:
Put these lines,
Spinner sp = (Spinner) findViewById(R.id.spin);;
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.spinner_array , android.R.layout.simple_spinner_item);
in onCreate() of Activity after setContentView(R.layout.activity_spin_on_item );
Something like,
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_spin_on_item );
Spinner sp= (Spinner) findViewById(R.id.spin);;
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.spinner_array , android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setAdapter(adapter);
sp.performClick();
}
Update:2
From your activity_spin_on_item.xml File.
Look at Parent Tag,
<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"
tools:context=".SpinActivity" >
In this the attribute
tools:context=".SpinActivity"
should be tools:context=".SpinOnItemActivity"
回答2:
Spinner sp= (Spinner) findViewById(R.id.spin);;
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.spinner_array , android.R.layout.simple_spinner_item);
will come inside your onCreate() method after setContentView()
Edit: Then
sp.setAdapter(adapter);
TextView tview1 = (TextView)findViewById(R.id.testtxt );
will also come in onCreate() method after setContentView()
Edit:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_spin_on_item);
Spinner sp = (Spinner) findViewById(R.id.spin);
TextView tview1 = (TextView) findViewById(R.id.testtxt);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.spinner_array,
android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setAdapter(adapter);
sp.performClick();
}
public void onItemSelected(AdapterView<?> adapterView, View view, int i,
long l) {
String Name = (String) sp.getSelectedItem();
tview1.setText(Name);
}
来源：https://stackoverflow.com/questions/13798404/android-spinner-onitemselected