Java Android nullPointerException错误
Eclipse在我的代码中没有发现错误，但当我尝试在模拟器上运行应用程序时，它会打开，然后立即崩溃。Logcat给了我一个模糊的nullPointerException错误。我可以注释掉onKeyDown方法，然后它就可以正常运行了。但当然，我不能使用后退键返回，它只会关闭应用程序 我的代码如下：Java Android nullPointerException错误,java,android,eclipse,nullpointerexception,onkeydown,Java,Android,Eclipse,Nullpointerexception,Onkeydown,Eclipse在我的代码中没有发现错误，但当我尝试在模拟器上运行应用程序时，它会打开，然后立即崩溃。Logcat给了我一个模糊的nullPointerException错误。我可以注释掉onKeyDown方法，然后它就可以正常运行了。但当然，我不能使用后退键返回，它只会关闭应用程序 我的代码如下： import android.app.Activity; import android.graphics.Color; import android.os.Bundle; import android
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.ViewFlipper;
public class MainActivity extends Activity {
static String[] items = {"Campaign", "Multiplayer", "Zombies"};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView listView = (ListView) findViewById(R.id.listview);
final ViewFlipper viewflipper = (ViewFlipper) findViewById(R.id.viewflipper1);
listView.setAdapter(new BaseAdapter(){
public int getCount() {
return items.length;
}
public Object getItem(int position) {
return items[position];
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.list_row, null);
TextView textView = (TextView) view.findViewById(R.id.TextView01);
textView.setText(items[position]);
textView.setTextColor(Color.rgb(255,106,0));
textView.setTextSize(24);
TextView textView1 = (TextView) findViewById(R.id.textView1);
textView1.setTextColor(Color.rgb(255,106,0));
return view;
}});
listView.setOnItemClickListener(new OnItemClickListener(){
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
if (position == 0) {
viewflipper.showNext();
}if (position == 1) {
viewflipper.showNext();
viewflipper.showNext();
}if (position == 2) {
viewflipper.showNext();
viewflipper.showNext();
viewflipper.showNext();
}}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
ViewFlipper viewflipper = (ViewFlipper) findViewById(R.id.viewflipper1);
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
if(viewflipper.getDisplayedChild() == 0){
viewflipper.showPrevious();
}if(viewflipper.getDisplayedChild() == 1){
viewflipper.showPrevious();
viewflipper.showPrevious();
}if(viewflipper.getDisplayedChild() == 2){
viewflipper.showPrevious();
viewflipper.showPrevious();
viewflipper.showPrevious();
}
return true;
}
return super.onKeyDown(keyCode, event);
}
};
01-21 11:38:46.151: E/AndroidRuntime(760): FATAL EXCEPTION: main
01-21 11:38:46.151: E/AndroidRuntime(760): java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{com.example.blackopsiiexperience/com.example.blackopsiiexperience.MainActivity}: java.lang.NullPointerException
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.os.Handler.dispatchMessage(Handler.java:99)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.os.Looper.loop(Looper.java:137)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.main(ActivityThread.java:5039)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.reflect.Method.invokeNative(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.reflect.Method.invoke(Method.java:511)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-21 11:38:46.151: E/AndroidRuntime(760): at dalvik.system.NativeStart.main(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): Caused by: java.lang.NullPointerException
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.Activity.findViewById(Activity.java:1839)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.example.blackopsiiexperience.MainActivity.<init>(MainActivity.java:73)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.Class.newInstanceImpl(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.Class.newInstance(Class.java:1319)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
01-21 11:38:46.151: E/AndroidRuntime(760): ... 11 more
Any suggestions?
导入android.app.Activity；
导入android.graphics.Color；
导入android.os.Bundle；
导入android.view.KeyEvent；
导入android.view.LayoutInflater；
导入android.view.Menu；
导入android.view.view；
导入android.view.ViewGroup；
导入android.widget.AdapterView；
导入android.widget.AdapterView.OnItemClickListener；
导入android.widget.BaseAdapter；
导入android.widget.ListView；
导入android.widget.TextView；
导入android.widget.ViewFlipper；
公共类MainActivity扩展了活动{
静态字符串[]项={“活动”、“多人”、“僵尸”}；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
ListView ListView=（ListView）findViewById（R.id.ListView）；
最终ViewFlipper ViewFlipper=（ViewFlipper）findViewById（R.id.viewflipper1）；
setAdapter（新的BaseAdapter（）{
public int getCount（）{
返回项目。长度；
}
公共对象getItem（int位置）{
退货项目[位置]；
}
公共长getItemId（int位置）{
返回位置；
}
公共视图getView（int位置、视图转换视图、视图组父视图）{
LayoutFlater充气机=（LayoutFlater）getSystemService（布局充气机服务）；
视图=充气机。充气（R.layout.list\u行，空）；
TextView TextView=（TextView）view.findViewById（R.id.TextView01）；
textView.setText（项目[位置]）；
setTextColor（Color.rgb（255106,0））；
textView.setTextSize（24）；
TextView textView1=（TextView）findViewById（R.id.textView1）；
textView1.setTextColor（Color.rgb（255106,0））；
返回视图；
}});
setOnItemClickListener（新的OnItemClickListener（）{
公共视图单击（适配器视图a、视图v、内部位置、长id）{
如果（位置==0）{
viewflipper.showNext（）；
}如果（位置==1）{
viewflipper.showNext（）；
viewflipper.showNext（）；
}如果（位置==2）{
viewflipper.showNext（）；
viewflipper.showNext（）；
viewflipper.showNext（）；
}}
});
}
@凌驾
公共布尔onCreateOptions菜单（菜单）{
getMenuInflater（）.充气（R.menu.activity\u主菜单）；
返回true；
}
ViewFlipper ViewFlipper=（ViewFlipper）findViewById（R.id.viewflipper1）；
@凌驾
公共布尔onKeyDown（int-keyCode，KeyEvent事件）{
if（keyCode==KeyEvent.keyCode\u BACK&&event.getRepeatCount（）==0）{
if（viewflipper.getDisplayedChild（）==0）{
viewflipper.showPrevious（）；
}if（viewflipper.getDisplayedChild（）==1）{
viewflipper.showPrevious（）；
viewflipper.showPrevious（）；
}if（viewflipper.getDisplayedChild（）==2）{
viewflipper.showPrevious（）；
viewflipper.showPrevious（）；
viewflipper.showPrevious（）；
}
返回true；
}
返回super.onKeyDown（keyCode，event）；
}
};
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.ViewFlipper;
public class MainActivity extends Activity {
static String[] items = {"Campaign", "Multiplayer", "Zombies"};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView listView = (ListView) findViewById(R.id.listview);
final ViewFlipper viewflipper = (ViewFlipper) findViewById(R.id.viewflipper1);
listView.setAdapter(new BaseAdapter(){
public int getCount() {
return items.length;
}
public Object getItem(int position) {
return items[position];
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.list_row, null);
TextView textView = (TextView) view.findViewById(R.id.TextView01);
textView.setText(items[position]);
textView.setTextColor(Color.rgb(255,106,0));
textView.setTextSize(24);
TextView textView1 = (TextView) findViewById(R.id.textView1);
textView1.setTextColor(Color.rgb(255,106,0));
return view;
}});
listView.setOnItemClickListener(new OnItemClickListener(){
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
if (position == 0) {
viewflipper.showNext();
}if (position == 1) {
viewflipper.showNext();
viewflipper.showNext();
}if (position == 2) {
viewflipper.showNext();
viewflipper.showNext();
viewflipper.showNext();
}}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
ViewFlipper viewflipper = (ViewFlipper) findViewById(R.id.viewflipper1);
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
if(viewflipper.getDisplayedChild() == 0){
viewflipper.showPrevious();
}if(viewflipper.getDisplayedChild() == 1){
viewflipper.showPrevious();
viewflipper.showPrevious();
}if(viewflipper.getDisplayedChild() == 2){
viewflipper.showPrevious();
viewflipper.showPrevious();
viewflipper.showPrevious();
}
return true;
}
return super.onKeyDown(keyCode, event);
}
};
01-21 11:38:46.151: E/AndroidRuntime(760): FATAL EXCEPTION: main
01-21 11:38:46.151: E/AndroidRuntime(760): java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{com.example.blackopsiiexperience/com.example.blackopsiiexperience.MainActivity}: java.lang.NullPointerException
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.os.Handler.dispatchMessage(Handler.java:99)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.os.Looper.loop(Looper.java:137)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.main(ActivityThread.java:5039)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.reflect.Method.invokeNative(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.reflect.Method.invoke(Method.java:511)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-21 11:38:46.151: E/AndroidRuntime(760): at dalvik.system.NativeStart.main(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): Caused by: java.lang.NullPointerException
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.Activity.findViewById(Activity.java:1839)
01-21 11:38:46.151: E/AndroidRuntime(760): at com.example.blackopsiiexperience.MainActivity.<init>(MainActivity.java:73)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.Class.newInstanceImpl(Native Method)
01-21 11:38:46.151: E/AndroidRuntime(760): at java.lang.Class.newInstance(Class.java:1319)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
01-21 11:38:46.151: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
01-21 11:38:46.151: E/AndroidRuntime(760): ... 11 more
Any suggestions?
01-21 11:38:46.151:E/AndroidRuntime（760）：致命异常：main
01-21 11:38:46.151:E/AndroidRuntime（760）：java.lang.RuntimeException:无法实例化活动
ComponentInfo{com.example.BlackOpsiieExperience/com.example.BlackOpsiieExperience.MainActivity}:java.lang.NullPointerException
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2106）
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230）
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.ActivityThread.access$600（ActivityThread.java:141）
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1234）
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.os.Handler.dispatchMessage（Handler.java:99）上
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.os.Looper.loop（Looper.java:137）上
01-21 11:38:46.151:E/AndroidRuntime（760）：位于android.app.ActivityThread.main（ActivityThread.java:5039）
01-21 11:38:46.151:E/AndroidRuntime（760）：位于java.lang.reflect.Method.Invokenactive（本机方法）
01-21 11:38:46.151:E/AndroidRuntime（760）：在java.lang.reflect.Method.invoke（Method.java:511）
01-21 11:38:46.151:E/AndroidRuntime（760）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:793）
01-21 11:38:46.151:E/AndroidRuntime（760）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:560）
01-21 11:38:46.151:E/AndroidRuntime（760）：在dalvik.system.NativeStart.main（本机方法）
01-21 11:38:46.151:E/AndroidRuntime（760）：由以下原因引起：java.lang.NullPointerException
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.Activity.findViewById（Activity.java:1839）
01-21 11:38:46.151:E/AndroidRuntime（760）：在com.example.blackOpsiieExperience.MainActivity。（MainActivity.java:73）
01-21 11:38:46.151:E/AndroidRuntime（760）：位于java.lang.Class.newInstanceImpl（本机方法）
01-21 11:38:46.151:E/AndroidRuntime（760）：在java.lang.Class.newInstance（Class.java:1319）上
01-21 11:38:46.151:E/AndroidRuntime（760）：在android.app.Instrumentati