Android 下拉微调器仅加载列表中的第一项,然后在按下时返回NullPointerException
这是我第一次在我的android应用程序中构建微调器,我搜索了不同的网站,这些网站为相同的目的发布了不同的教程,我发现我实现的微调器与他们一样 我的应用程序运行成功,按下手机屏幕上第一个出现的项目后返回空指针异常 这是我在logcat上的例外Android 下拉微调器仅加载列表中的第一项,然后在按下时返回NullPointerException,android,android-layout,nullpointerexception,android-spinner,Android,Android Layout,Nullpointerexception,Android Spinner,这是我第一次在我的android应用程序中构建微调器,我搜索了不同的网站,这些网站为相同的目的发布了不同的教程,我发现我实现的微调器与他们一样 我的应用程序运行成功,按下手机屏幕上第一个出现的项目后返回空指针异常 这是我在logcat上的例外 11-01 04:15:40.669 23134-23134/com.example.prof_mohamedatef.listview E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPoint
11-01 04:15:40.669 23134-23134/com.example.prof_mohamedatef.listview E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:392)
at android.widget.ArrayAdapter.getDropDownView(ArrayAdapter.java:416)
at android.support.v7.widget.AppCompatSpinner$DropDownAdapter.getDropDownView(AppCompatSpinner.java:636)
at android.support.v7.widget.AppCompatSpinner$DropDownAdapter.getView(AppCompatSpinner.java:631)
at android.support.v7.widget.AppCompatSpinner.compatMeasureContentWidth(AppCompatSpinner.java:558)
at android.support.v7.widget.AppCompatSpinner.access$500(AppCompatSpinner.java:65)
at android.support.v7.widget.AppCompatSpinner$DropdownPopup.computeContentWidth(AppCompatSpinner.java:749)
at android.support.v7.widget.AppCompatSpinner$DropdownPopup.show(AppCompatSpinner.java:774)
at android.support.v7.widget.AppCompatSpinner.performClick(AppCompatSpinner.java:432)
at android.view.View$PerformClick.run(View.java:18339)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5283)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)
我的代码如下:
将列表分配给阵列适配器
public class Home extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Spinner spinner=(Spinner) findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(this);
//Spinner Drop Down elements
List<String> rooms_num=new ArrayList<String>();
rooms_num.add("1 room");
rooms_num.add("2 rooms");
rooms_num.add("3 rooms");
rooms_num.add("4 rooms");
rooms_num.add("5 rooms");
rooms_num.add("6 rooms");
//Adapter for Spinner
ArrayAdapter<String> roomsNumAdapter=new ArrayAdapter<String>(this, R.layout.spinner_layout_text, R.id.spinnerItem, rooms_num);
roomsNumAdapter.setDropDownViewResource(R.layout.spinner_layout_row);
spinner.setAdapter(roomsNumAdapter);
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String item = parent.getItemAtPosition(position).toString();
Toast.makeText(parent.getContext(), "Selected: " + item, Toast.LENGTH_LONG).show();
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
}
公共类Home扩展AppCompativeActivity实现AdapterView.OnItemSelectedListener{
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
微调器微调器=(微调器)findViewById(R.id.Spinner);
spinner.setOnItemSelectedListener(此);
//微调器下拉元素
List rooms_num=new ArrayList();
增加房间数量(“1个房间”);
房间数量增加(“2个房间”);
房间数量增加(“3个房间”);
房间数量增加(“4个房间”);
房间数量增加(“5个房间”);
房间数量增加(“6个房间”);
//纺纱机转接器
ArrayAdapter RoomsUMadapter=新的ArrayAdapter(此,R.layout.spinner\u layout\u text,R.id.spinnerItem,rooms\u num);
roomsNumAdapter.setDropDownViewResource(R.layout.spinner\u layout\u row);
旋转器。设置适配器(roomsNumAdapter);
}
@凌驾
已选择公共视图(AdapterView父视图、视图视图、整型位置、长id){
String item=parent.getItemAtPosition(position.toString();
Toast.makeText(parent.getContext(),“Selected:”+项,Toast.LENGTH_LONG.show();
}
@凌驾
未选择公共无效(AdapterView父级){
}
}
我在不同的网站上发现我的微调器使用了两个xml布局文件,
第一个是:
spinner\u layout\u row.xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/spinner_list"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="1dip" >
<TextView
android:id="@+id/spinnerItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="2dp"
android:textSize="12sp" >
</TextView>
</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<ScrollView android:id="@+id/scrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout 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=".Home"
android:background="#03122F"
android:padding="10dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="@+id/txt_LoggedInUser_Title"
android:layout_width="wrap_content"
android:layout_weight="1"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" android:text="Welcome" />
<TextView
android:id="@+id/txt_LoggedInUser_TYPE"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#D4D4D8"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/txt_LoggedInUser"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="6">
<Spinner
android:background="#FFF"
android:layout_margin="5dp"
android:id="@+id/spinner"
android:textStyle="bold"
android:textSize="15sp"
android:layout_gravity="center"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
/>
</LinearLayout>
</LinearLayout>
</ScrollView>
第二个是:
spinner\u layout\u text.xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/spinner_list"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="1dip" >
<TextView
android:id="@+id/spinnerItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="2dp"
android:textSize="12sp" >
</TextView>
</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<ScrollView android:id="@+id/scrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout 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=".Home"
android:background="#03122F"
android:padding="10dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="@+id/txt_LoggedInUser_Title"
android:layout_width="wrap_content"
android:layout_weight="1"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" android:text="Welcome" />
<TextView
android:id="@+id/txt_LoggedInUser_TYPE"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#D4D4D8"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/txt_LoggedInUser"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="6">
<Spinner
android:background="#FFF"
android:layout_margin="5dp"
android:id="@+id/spinner"
android:textStyle="bold"
android:textSize="15sp"
android:layout_gravity="center"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
/>
</LinearLayout>
</LinearLayout>
</ScrollView>
最后,这是我的活动xml布局文件:
activity\u home.xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/spinner_list"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="1dip" >
<TextView
android:id="@+id/spinnerItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="2dp"
android:textSize="12sp" >
</TextView>
</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<ScrollView android:id="@+id/scrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout 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=".Home"
android:background="#03122F"
android:padding="10dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="@+id/txt_LoggedInUser_Title"
android:layout_width="wrap_content"
android:layout_weight="1"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" android:text="Welcome" />
<TextView
android:id="@+id/txt_LoggedInUser_TYPE"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#D4D4D8"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/txt_LoggedInUser"
android:layout_width="wrap_content"
android:layout_weight="2"
android:textColor="#FFF"
android:padding="5dp"
android:textStyle="bold"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="6">
<Spinner
android:background="#FFF"
android:layout_margin="5dp"
android:id="@+id/spinner"
android:textStyle="bold"
android:textSize="15sp"
android:layout_gravity="center"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
/>
</LinearLayout>
</LinearLayout>
</ScrollView>
谢谢你的帮助。
谢谢尝试像这样编辑您的微调器\u布局\u text.xml
<TextView
android:id="@+id/spinnerItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="1dip"
android:padding="2dp"
android:textSize="12sp">
</TextView>
我认为问题在于你给relativeLayout提供了方向性,它只在线性布局的情况下有效ArrayAdapter RoomsNameDapter=new ArrayAdapter(这是android.R.layout.simple\u list\u item\u 2,rooms\u num);
ArrayAdapter<String> roomsNumAdapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_2,rooms_num);
或者使用customadapter尝试使用
parent.getAdapter().getItem(位置)
而不是parent.getItemAtPosition(位置)
。这会将您的onItemSelected()方法更改为类似以下内容:
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String item = parent.getAdapter().getItem(position).toString();
Toast.makeText(parent.getContext(), "Selected: " + item, Toast.LENGTH_LONG).show();
}
@覆盖
已选择公共视图(AdapterView父视图、视图视图、整型位置、长id){
String item=parent.getAdapter().getItem(position.toString();
Toast.makeText(parent.getContext(),“Selected:”+项,Toast.LENGTH_LONG.show();
}
编辑
替换:
ArrayAdapter<String> roomsNumAdapter=new ArrayAdapter<String>(this,R.layout.spinner_layout_text,rooms_num);
roomsNumAdapter.setDropDownViewResource(R.layout.spinner_layout_row);
spinner.setAdapter(roomsNumAdapter);
ArrayAdapter roomsNumAdapter=新的ArrayAdapter(this,R.layout.spinner\u layout\u text,rooms\u num);
roomsNumAdapter.setDropDownViewResource(R.layout.spinner\u layout\u row);
旋转器。设置适配器(roomsNumAdapter);
与:
ArrayAdapter roomsNumAdapter=新的ArrayAdapter(这个,R.layout.spinner\u layout\u text,R.id.spinnerItem,rooms\u num);
旋转器。设置适配器(roomsNumAdapter);
初始化微调器后:
spinner = (Spinner) findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(this);
//Spinner Drop Down elements
ArrayList<String> rooms_num = new ArrayList<String>();
rooms_num.add("1");
rooms_num.add("2");
rooms_num.add("3");
rooms_num.add("4");
rooms_num.add("5");
rooms_num.add("6");
CustomSpinnerAdapter customSpinnerAdapter=new CustomSpinnerAdapter(getApplicationContext(),rooms_num);
spinner.setAdapter(customSpinnerAdapter);
spinner=(spinner)findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(此);
//微调器下拉元素
ArrayList房间数=新建ArrayList();
房间数量增加(“1”);
房间数量增加(“2”);
房间数量增加(“3”);
房间数量增加(“4”);
房间数量增加(“5”);
房间数量增加(“6”);
CustomSpinnerAdapter CustomSpinnerAdapter=新的CustomSpinnerAdapter(getApplicationContext(),房间数量);
spinner.setAdapter(自定义SpinNerAdapter);
为名为CustomSpinnerAdapter的微调器使用自定义适配器,如下所示:
package mo.ed.prof_mohamedatef.yourbestonlinetv;
import android.content.Context;
import android.graphics.Color;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import java.util.ArrayList;
/**
* Created by Prof-Mohamed Atef on 11/1/2016.
*/
public class CustomSpinnerAdapter extends BaseAdapter {
private final Context mContext;
private ArrayList<String> SpinnerFeedItemList;
public CustomSpinnerAdapter(Context mContext, ArrayList<String> spinnerFeedItemList) {
this.mContext= mContext;
SpinnerFeedItemList = spinnerFeedItemList;
}
@Override
public int getCount() {
return SpinnerFeedItemList.size();
}
@Override
public Object getItem(int position) {
return SpinnerFeedItemList.get(position);
}
@Override
public long getItemId(int position) {
return (long) position;
}
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
TextView txt = new TextView(mContext);
txt.setPadding(16, 16, 16, 16);
txt.setTextSize(18);
txt.setGravity(Gravity.CENTER_VERTICAL);
txt.setText(SpinnerFeedItemList.get(position));
txt.setTextColor(Color.parseColor("#000000"));
return txt;
}
TextView txt;
@Override
public View getView(int position, View convertView, ViewGroup parent) {
txt = new TextView(mContext);
txt.setGravity(Gravity.CENTER);
txt.setPadding(10, 10, 10, 10);
txt.setTextSize(16);
txt.setText(SpinnerFeedItemList.get(position));
txt.setTextColor(Color.parseColor("#000000"));
txt.setBackgroundResource(R.color.yellow);
return txt;
}
}
package mo.ed.prof_mohamedatef.yourbestonlinev;
导入android.content.Context;
导入android.graphics.Color;
导入android.view.Gravity;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.BaseAdapter;
导入android.widget.TextView;
导入java.util.ArrayList;
/**
*由Mohamed Atef教授于2016年11月1日创建。
*/
公共类CustomSpinerAdapter扩展BaseAdapter{
私有最终上下文mContext;
私有ArrayList SpinnerFeedItemList;
公共CustomSpinnerAdapter(上下文mContext、ArrayList spinnerFeedItemList){
this.mContext=mContext;
SpinnerFeedItemList=SpinnerFeedItemList;
}
@凌驾
public int getCount(){
返回喷丝头FeedItemList.size();
}
@凌驾
公共对象getItem(int位置){
返回喷丝板FeedItemList.get(位置);
}
@凌驾
公共长getItemId(int位置){
返回(长)位置;
}
@凌驾
公共视图getDropDownView(int位置、视图转换视图、视图组父视图){
TextView txt=新的TextView(mContext);
setPadding(16,16,16,16);
txt.setTextSize(18);
txt.setGravity(重心垂直);
setText(SpinnerFeedItemList.get(position));
txt.setTextColor(Color.parseColor(#000000”);
返回txt;
}
文本视图;
@凌驾
公共视图getView(int位置、视图转换视图、视图组父视图){
txt=新文本视图(mContext);
txt.setGravity(Gravity.CENTER);
setPadding(10,10,10,10);
txt.setTextSize(16);
setText(SpinnerFeedItemList.get(position));
txt.setTextColor(Color.parseColor(#000000”);
txt.setBackgroundResource(R.color.yellow);
返回txt;
}
}
最后,它成功地工作了。感谢您的回复。您为什么有L