为什么程序一直提示错误
这是我的Java文件
package com.example.spinner;
import java.util.ArrayList;
import java.util.List;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.os.Build;
public class MainActivity extends Activity {
private TextView textview;
private Spinner spinner;
private List<String>list;
private ArrayAdapter<String>adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textview=(TextView) findViewById(R.id.textview);
spinner=(Spinner) findViewById(R.id.spinner);
//1:设置数据源、
list=new ArrayList<String>();
list.add("北京");
list.add("上海");
list.add("深圳");
list.add("广州");
//2：新建数组适配器
adapter=new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, list);
//3:设置下拉列表样式
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//4:加载适配器
spinner.setAdapter(adapter);
}
}这是我的xml文件
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/textview" android:layout_width="match_parent" android:layout_height="wrap_content" android:textSize="25sp" android:textColor="#ff0000" /> <Spinner android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/spinner" /> </LinearLayout>
这是我的日志
07-18 14:52:31.343: D/AndroidRuntime(1593): Shutting down VM
07-18 14:52:31.343: W/dalvikvm(1593): threadid=1: thread exiting with uncaught exception (group=0xa61ea908)
07-18 14:52:31.347: E/AndroidRuntime(1593): FATAL EXCEPTION: main
07-18 14:52:31.347: E/AndroidRuntime(1593): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.spinner/com.example.spinner.MainActivity}: java.lang.NullPointerException
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.os.Handler.dispatchMessage(Handler.java:99)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.os.Looper.loop(Looper.java:137)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-18 14:52:31.347: E/AndroidRuntime(1593): at java.lang.reflect.Method.invokeNative(Native Method)
07-18 14:52:31.347: E/AndroidRuntime(1593): at java.lang.reflect.Method.invoke(Method.java:511)
07-18 14:52:31.347: E/AndroidRuntime(1593): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-18 14:52:31.347: E/AndroidRuntime(1593): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-18 14:52:31.347: E/AndroidRuntime(1593): at dalvik.system.NativeStart.main(Native Method)
07-18 14:52:31.347: E/AndroidRuntime(1593): Caused by: java.lang.NullPointerException
07-18 14:52:31.347: E/AndroidRuntime(1593): at com.example.spinner.MainActivity.onCreate(MainActivity.java:49)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.Activity.performCreate(Activity.java:5104)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-18 14:52:31.347: E/AndroidRuntime(1593): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-18 14:52:31.347: E/AndroidRuntime(1593): ... 11 more
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