ListView项没有显示在主活动上
ListView项没有显示在主活动上
提问于 2014-10-14 06:38:41
我是android开发的初学者。我试图使用Adapter从一个ArrayList的Workout项发送数据到MainActivity，但是我对基本适配器的理解不是很好。这是我的代码：
WorkoutActivity.java：
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.app.FragmentManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.os.SystemClock;
import android.preference.PreferenceManager;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.Chronometer;
import android.widget.TextView;
public class WorkoutActivity extends Activity {
WorkoutItemAdapter workoutItemAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_workout);
}
public class WorkoutItemAdapter extends BaseAdapter{
int rowCount = 1;
List<WorkoutItem> workoutsList = getDataForListView();
public WorkoutItem getWorkout(int position)
{
return workoutsList.get(position);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
LayoutInflater inflater = (LayoutInflater) WorkoutActivity.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.workout_item, parent, false);
}
TextView workoutNum = (TextView) convertView.findViewById(R.id.workout_col);
TextView workoutTime = (TextView) convertView.findViewById(R.id.time_col);
WorkoutItem workout = workoutsList.get(position);
workoutNum.setText(workout.workoutNum);
workoutTime.setText(workout.time);
return convertView;
}
@Override
public int getCount() {
return workoutsList.size();
// TODO Auto-generated method stub
}
@Override
public WorkoutItem getItem(int position) {
// TODO Auto-generated method stub
return workoutsList.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public void addRow() {
rowCount++;
notifyDataSetChanged();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.workout, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onBackPressed() {
moveTaskToBack(true);
}
public List<WorkoutItem> getDataForListView()
{
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
String workoutTime = prefs.getString("Workout Time", "");
List<WorkoutItem> workoutsList = new ArrayList<WorkoutItem>();
for(int i = 0; i < (workoutsList.size() + 1); i++)
{
WorkoutItem workout = new WorkoutItem();
workout.workoutNum = "Workout " + (i+1);
workout.time = workoutTime;
workoutsList.add(workout);
}
return workoutsList;
}
public void startAndStopTimer(View view)
{
long totalTime = 0;
Button startAndStop = (Button) findViewById(R.id.button1);
Chronometer c = (Chronometer) findViewById(R.id.chronometer1);
if(startAndStop.getText().equals("Start"))
{
c.setBase(SystemClock.elapsedRealtime() + totalTime);
c.start();
startAndStop.setText("Pause");
}
else
{
totalTime = c.getBase() - SystemClock.elapsedRealtime();
c.stop();
startAndStop.setText("Start");
}
}
public void save(View view)
{
// create broadcast receiver saying ...saved.
// Add ArrayList value to arrayList
Chronometer timer = (Chronometer) findViewById(R.id.chronometer1);
SharedPreferences timerSettings = PreferenceManager.getDefaultSharedPreferences(this);
Editor editor = timerSettings.edit();
editor.putString("Workout Time", timer.getText().toString());
editor.commit();
// go back to main activity.
Intent intent = new Intent(WorkoutActivity.this, OverviewActivity.class);
startActivity(intent);
finish();
}
public void cancel(View view)
{
// go back to main activity
Intent intent = new Intent(WorkoutActivity.this, OverviewActivity.class);
startActivity(intent);
finish();
}
}OverviewActivity.java：
import edu.uark.csce.razorrunner.WorkoutActivity.WorkoutItemAdapter;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;
public class OverviewActivity extends Activity{
WorkoutItemAdapter workoutAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_overview);
LoadPreferences();
LoadListView();
}
private void LoadListView() {
// TODO Auto-generated method stub
ListView workoutList = (ListView) findViewById(R.id.workout_list);
workoutList.setAdapter(workoutAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.overview, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void LoadPreferences()
{
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
String Name = sharedPreferences.getString("Name", "");
TextView textView = (TextView) findViewById(R.id.textView2);
textView.setText(Name);
}
public void openWorkoutActivity(View view)
{
Intent intent = new Intent(OverviewActivity.this, WorkoutActivity.class);
startActivity(intent);
finish();
}
public void openProfileActivity(View view)
{
Intent intent = new Intent(OverviewActivity.this, ProfileActivity.class);
startActivity(intent);
finish();
}
public void openHistoryActivity(View view)
{
Intent intent = new Intent(OverviewActivity.this, HistoryActivity.class);
startActivity(intent);
finish();
}
}activity_overview.xml：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="edu.uark.csce.razorrunner.OverviewActivity" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<Button
android:id="@+id/profileButton"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:onClick="openProfileActivity"
android:text="Profile" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:text="Name"
android:textAppearance="?android:attr/textAppearanceLarge" />
</RelativeLayout>
<ListView
android:id="@+id/workout_list"
android:layout_width="wrap_content"
android:layout_height="195dp"
android:layout_weight="0.19" >
</ListView>
<Button
android:id="@+id/startNewWorkout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="0"
android:onClick="openWorkoutActivity"
android:text="Start New Workout!"
android:typeface="sans" />
</LinearLayout>activity_workout.xml：
<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"
android:gravity="center"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="edu.uark.csce.razorrunner.WorkoutActivity" >
<Button
android:id="@+id/Button01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button2"
android:layout_alignBottom="@+id/button2"
android:layout_alignRight="@+id/button1"
android:text="Cancel"
android:onClick="cancel" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_toLeftOf="@+id/Button01"
android:text="Save"
android:onClick="save" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/Button01"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_marginRight="22dp"
android:text="Start"
android:onClick="startAndStopTimer" />
<TextView
android:id="@+id/time_col"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView2"
android:layout_alignParentTop="true"
android:text="New Workout"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/time_col"
android:layout_marginTop="18dp"
android:text="Calories Burned"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/TextView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView2"
android:layout_below="@+id/textView2"
android:layout_marginTop="14dp"
android:text="Duration"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/TextView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView2"
android:layout_alignBottom="@+id/textView2"
android:layout_alignRight="@+id/button1"
android:layout_toRightOf="@+id/button2"
android:ems="10"
android:text="0"
android:textAppearance="?android:attr/textAppearanceLarge">
<requestFocus />
</TextView>
<Chronometer
android:id="@+id/chronometer1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/TextView01"
android:layout_alignLeft="@+id/TextView1"
android:layout_alignRight="@+id/TextView1"
android:text="Chronometer" />
</RelativeLayout>我想显示每次单击“保存”时每个列表项的锻炼次数和持续时间，但目前，每次单击“保存”都会得到一个空白的ListView。关于这一主题的任何帮助和/或补充资料都是有用的。
Stack Overflow用户
发布于 2014-10-14 07:10:11
你还没有初始化workoutAdapter...only声明..。因此，workoutAdapter is null....which意味着适配器的大小为0，...which表示列表视图中没有行.
在将适配器设置为listview之前，..you必须初始化workoutAdapter，即
workoutAdapter=new WorkoutItemAdapter(getDataForListView());创建渐缩构造器并传递列表数组
public class WorkoutItemAdapter extends BaseAdapter{
int rowCount = 1; //don't know about that
List<WorkoutItem> workoutsList;
public WorkoutItemAdapter(List<WorkoutItem> tmp)
{
this.workoutsList=tmp; //setting the list array to datamember of this adapter
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/26354161
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