出于某种原因，我无法弄清楚如何将自定义布局文件添加到我的列表视图中，我几乎尝试了所有教程，但我仍然缺少此过程中的链接，所以这就是为什么我转向你们。
到目前为止我发现我需要一个自定义适配器来扩展常规arrayadapter。
ReminderAdapter.java
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import java.util.ArrayList;
public class ReminderAdapter extends ArrayAdapter<ReminderObject> {
private ArrayList<ReminderObject> items;
private Context context;
public ReminderAdapter(Context context, int textViewResourceId, ArrayList<ReminderObject> items) {
super(context, textViewResourceId, items);
this.items = items;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.reminder_row, null);
}
ReminderObject o = items.get(position);
if (o != null) {
TextView txtTime = (TextView) v.findViewById(R.id.txtTime);
}
return v;
}
}
我也知道，每个属性都需要一个带有getter和setter的对象
class ReminderObject {
int _id, _hours, _minutes;
public ReminderObject(){}
public ReminderObject(int _hours, int _minutes){
this._hours = _hours;
this._minutes = _minutes;
}
public ReminderObject(int id, int _hours, int _minutes){
this._id = id;
this._hours = _hours;
this._minutes = _minutes;
}
public int getIdentifier(){
return this._id;
}
public void setIdentifier(int id){
this._id = id;
}
public int getHours(){
return this._hours;
}
public void setHours(int hours){
this._hours = hours;
}
public int getMinutes(){
return this._minutes;
}
public void setMinutes(int minutes){
this._minutes = minutes;
}
}
在这里，我得到了自定义布局文件
<?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="horizontal"
android:padding="5dip" >
<TextView
android:id="@+id/txtTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#040404"
android:typeface="sans"
android:textSize="15dip"
android:textStyle="bold"/>
<ImageView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/trash"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"/>
</RelativeLayout>
我的数据库处理程序类
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class dbHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "remindersDB";
private static final String TABLE_NAME = "reminders";
private static final String KEY_ID = "id";
private static final String KEY_HOURS = "hours";
private static final String KEY_MINUTES = "minutes";
public dbHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE =
"CREATE TABLE " + TABLE_NAME + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_HOURS + " INTEGER,"
+ KEY_MINUTES + " INTEGER" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
void addReminder(ReminderObject reminder) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_HOURS, reminder.getHours());
values.put(KEY_MINUTES, reminder.getMinutes());
db.insert(TABLE_NAME, null, values);
db.close();
}
public ArrayList getAllReminders()
{
ArrayList reminderList = new ArrayList();
String selectQuery = "SELECT * FROM " + TABLE_NAME;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
if (cursor.moveToFirst()) {
do {
ReminderObject reminder = new ReminderObject();
reminderList.add(cursor.getInt(1) + ":" + cursor.getInt(2));
} while (cursor.moveToNext());
}
return reminderList;
}
public void deleteReminder(ReminderObject reminderobject) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_NAME, KEY_ID + " = ?", new String[] { String.valueOf(reminderobject.getIdentifier()) });
db.close();
}
public void deleteAllReminders() {
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL("DELETE FROM " + TABLE_NAME);
db.execSQL("VACUUM");
}
}
我在活动中调用的最终方法填写列表
private void populateListView() {
dbHandler dbConnection = new dbHandler(getApplicationContext());
ListView lvReminders = (ListView) findViewById(android.R.id.list);
List reminders = dbConnection.getAllReminders();
ReminderAdapter adapter = new ReminderAdapter(this, R.layout.reminder_row, reminders);
lvReminders.setAdapter(adapter);
}
导致应用程序关闭的错误
05-05 21:32:17.506 9042-9042/nl.co.hoofdpijn E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at nl.co.hoofdpijn.ReminderAdapter.getView(ReminderAdapter.java:25)
at android.widget.AbsListView.obtainView(AbsListView.java:2465)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
at android.widget.ListView.onMeasure(ListView.java:1162)
at android.view.View.measure(View.java:15288)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1396)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15288)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:15288)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1396)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15288)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2397)
at android.view.View.measure(View.java:15288)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1974)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1217)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1390)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1113)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4481)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
at android.view.Choreographer.doCallbacks(Choreographer.java:555)
at android.view.Choreographer.doFrame(Choreographer.java:525)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4867)
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:1007)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
at dalvik.system.NativeStart.main(Native Method)
规则25：LayoutInflater vi =（LayoutInflater）context.getSystemService（Context.LAYOUT_INFLATER_SERVICE）;
答案 0 :(得分：1)
在您的情况下，上下文似乎为null。你有私有变量＆＃39; context＆＃39;但你永远不会为它分配任何价值。
更改适配器的构造函数，如下所示，它应修复NPE：
public ReminderAdapter（Context context，int textViewResourceId，ArrayList items）
{
super（context，textViewResourceId，items）;
this.items = items;
this.context = context;
}