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我有一個包含培訓列表的Mainactivity。並且在每個列表上單擊它開始整個應用程序中相同訓練的會話。 我設法使用Singleton並將其訪問到我的主要活動中。但onItemClick它需要對話框和按鈕單擊對話框內，它應該採取其他活動。現在我得到一個錯誤，如java NullPointerException。這是下面的代碼; 請記住：我也想在第二項活動中進行同樣的訓練。將同一個對象從一個活動傳遞給另一個活動
MainActivity class;
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
currentTraining = (Training)arg0.getAdapter().getItem(arg2);
Log.i("DEBUG", currentTraining.getTitle());
CurrentTraining.getInstance().setTraining(currentTraining);
Toast.makeText(
getApplicationContext(),
"You clicked on position : " + arg2 + " and ID : "
+ currentTraining.getId(), Toast.LENGTH_LONG).show();
dialog = new Dialog(MainActivity.this);
dialog.setContentView(R.layout.dialog);
dialog.setTitle(currentTraining.getTitle());
TextView description = (TextView) dialog.findViewById(R.id.textView1);
description.setText("Description: " + currentTraining.getDescription());
TextView location = (TextView) dialog.findViewById(R.id.textView2);
location.setText("Location: " + currentTraining.getLocation());
TextView date = (TextView) dialog.findViewById(R.id.textView3);
date.setText("Date: " + currentTraining.getDate());
Button back_btn = (Button) dialog.findViewById(R.id.button1);
back_btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
dialog.dismiss();
}
});
Button start_btn = (Button) dialog.findViewById(R.id.button2);
start_btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent(MainActivity.this,
TraineeActivity.class);
//intent.putExtra("trainingId", currentTraining.getId());
//intent.putExtra("title", currentTraining.getTitle().toString());
MainActivity.this.startActivity(intent);
}
});
dialog.show();
}
而在第二個Activity Class中;
Training currentTraining;
private ListView personNamesListView;
// Adapter to made the connection between ListView UI component and SQLite data set.
private ListAdapter traineeListAdapter;
private TextView TitleView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.trainees);
currentTraining = CurrentTraining.getInstance().setTraining(currentTraining);
Log.i("DEBUG", ""+currentTraining.getTitle());
TitleView = (TextView)findViewById(R.id.training_title);
TitleView.setText(currentTraining.getTitle());
Button addnew = (Button) findViewById(R.id.add_btn);
addnew.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent(TraineeActivity.this,
FormActivity.class);
TraineeActivity.this.startActivity(intent);
}
});
personNamesListView = (ListView) findViewById(R.id.traineeslist);
// Create a list that contains only full name of the trainee
traineeListAdapter = new ArrayAdapter<Trainee>(this,
android.R.layout.simple_list_item_1, currentTraining.getTraineeArrayList());
personNamesListView.setAdapter(traineeListAdapter);
}
protected void onResume(){
super.onResume();
traineeListAdapter = new ArrayAdapter<Trainee>(this, android.R.layout.simple_list_item_1, currentTraining.getTraineeArrayList());
personNamesListView.setAdapter(traineeListAdapter);
}
我的單例類：
public class CurrentTraining {
private Training training ; //Training is my model class
private static CurrentTraining instance;
private CurrentTraining() {
}
public static CurrentTraining getInstance() {
if (instance == null)
instance = new CurrentTraining();
return instance;
}
public Training getTraining() {
return training;
}
public Training setTraining(Training training) {
return this.training = training;
}
}